Medical Nutrition Therapy and Weight Loss Questions for the Evidence Analysis Library Prevention of Type 2 Diabetes Project: Systematic Reviews

Abstract

Background:
Eleven recommendations, based on systematic reviews, were developed for the Evidence Analysis Library's prevention of type 2 diabetes project. Two recommendations, medical nutrition therapy (MNT) and weight loss, were rated strong.

Objective:
Present the basis of systematic reviews for MNT and weight loss recommendations.

Methods:
Literature searches using Medline were conducted to identify studies that met eligibility criteria. The MNT literature search covered a time span of 1995 to 2012, the weight loss literature search covered 2008 to 2012 due to inclusion of a Cochrane Review meta-analysis of randomized controlled trials (RCTs) published in 2008. Eligibility criteria for inclusion of articles included original research using higher-quality study designs (ie, RCTs, case control, cohort, crossover, and nonrandomized trials) with participants aged >18 years and meeting prediabetes or metabolic syndrome diagnostic criteria. MNT was defined as individualized and delivered by a registered dietitian nutritionist or international equivalent and length of weight loss interventions was ≥3 months.

Main outcome measures:
Two-hour postprandial blood glucose level, glycated hemoglobin level, albumin-to-creatinine ratio (metabolic syndrome samples only), fasting blood glucose level, high-density lipoprotein cholesterol level, systolic and diastolic blood pressure, triglyceride levels, urinary albumin excretion rate (metabolic syndrome samples only), waist circumference (WC), and waist-to-hip ratio were evaluated.

Results:
For MNT, 11 publications were included, with all 11 using an RCT study design and 10 including participants with prediabetes. A majority of publications reported significant improvements in glycemic outcomes, WC, and blood pressure. For weight loss, 28 publications were identified, with one meta-analysis (only included RCTs) and 20 publications using an RCT study design, with the meta-analysis and 10 RCTs including participants with prediabetes. A majority of publications reported significant improvements in glycemic outcomes, triglyceride level, WC, and blood pressure.

Conclusions:
Systematic reviews provided strong evidence that MNT and weight loss alter clinical parameters in ways that should reduce the risk of developing type 2 diabetes.

Full text

RESEARCH
Review
Medical Nutrition Therapy and Weight Loss
Questions for the Evidence Analysis Library
Prevention of Type 2 Diabetes Project:
Systematic Reviews
Hollie A. Raynor, PhD, RD, LDN; Patricia G. Davidson, DCN, MS, RDN; Heather Burns, MEd, RD, LD; Micki D. Hall Nadelson, MS, RD, LD;
Shelley Mesznik, MA, RD; Virginia Uhley, PhD, RDN; Lisa Moloney, MS, RD, LD
ARTICLE INFORMATION
Article history:
Submitted 25 July 2016
Accepted 20 June 2017
Keywords:
Prediabetes
Metabolic syndrome
Medical nutrition therapy
Weight loss
Evidence Analysis Library
2212-2672/Copyright ª2017 by the Academy of
Nutrition and Dietetics.
http://dx.doi.org/10.1016/j.jand.2017.06.361
ABSTRACT
Background Eleven recommendations, based on systematic reviews, were developed
for the Evidence Analysis Library’s prevention of type 2 diabetes project. Two recom-
mendations, medical nutrition therapy (MNT) and weight loss, were rated strong.
Objective Present the basis of systematic reviews for MNT and weight loss
recommendations.
Methods Literature searches using Medline were conducted to identify studies that
met eligibility criteria. The MNT literature search covered a time span of 1995 to 2012,
the weight loss literature search covered 2008 to 2012 due to inclusion of a Cochrane
Review meta-analysis of randomized controlled trials (RCTs) published in 2008. Eligi-
bility criteria for inclusion of articles included original research using higher-quality
study designs (ie, RCTs, case control, cohort, crossover, and nonrandomized trials)
with participants aged >18 years and meeting prediabetes or metabolic syndrome
diagnostic criteria. MNT was defined as individualized and delivered by a registered
dietitian nutritionist or international equivalent and length of weight loss interventions
was 3 months.
Main outcome measures Two-hour postprandial blood glucose level, glycated he-
moglobin level, albumin-to-creatinine ratio (metabolic syndrome samples only), fasting
blood glucose level, high-density lipoprotein cholesterol level, systolic and diastolic
blood pressure, triglyceride levels, urinary albumin excretion rate (metabolic syndrome
samples only), waist circumference (WC), and waist-to-hip ratio were evaluated.
Results For MNT, 11 publications were included, with all 11 using an RCT study design
and 10 including participants with prediabetes. A majority of publications reported
significant improvements in glycemic outcomes, WC, and blood pressure. For weight
loss, 28 publications were identified, with one meta-analysis (only included RCTs) and
20 publications using an RCT study design, with the meta-analysis and 10 RCTs
including participants with prediabetes. A majority of publications reported significant
improvements in glycemic outcomes, triglyceride level, WC, and blood pressure.
Conclusions Systematic reviews provided strong evidence that MNT and weight
loss alter clinical parameters in ways that should reduce the risk of developing type
2 diabetes.
J Acad Nutr Diet. 2017;117:1578-1611.
AT LOCAL, STATE, AND NATIONAL LEVELS, CONSID-
erable effort and expense are being directed toward
the prevention of type 2 diabetes mellitus (T2DM),
due to its increasing prevalence.
1
During 2011-2012,
the estimated prevalence of diabetes, defined by glycated
hemoglobin (HbA1c) level, fasting plasma glucose level, or
2-hour plasma glucose, was 14% among US adults.
2
Further-
more, one in three adults aged 65 years and older has dia-
betes,
2
creating the need for evidenced-based nutrition
recommendations for the prevention of T2DM. The population
at increased risk for developing T2DM are individuals with
insulin resistance, and within this population, the relative risk
for developing T2DM varies tremendously.
3
Thus, a hierar-
chical approach is suggested in determining those at greatest
risk for developing T2DM.
3
The highest risk group for devel-
oping T2DM includes individuals with prediabetes as defined
by the American Diabetes Association (ADA)
4
and/or metabolic
syndrome as defined by the National Cholesterol Education
Program’s Adult Treatment Panel III
5
or the World Health
Organization (WHO)
6
(see Table 1).
1578 JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS ª2017 by the Academy of Nutrition and Dietetics.

The prevalence of prediabetes, defined by HbA1c level,
fasting plasma glucose level, or 2-hour plasma glucose, was
38% in 2011-2012,
2
with the prevalence projected to increase
to 50% by 2050.
1
Similar to the prevalence of prediabetes, the
prevalence of metabolic syndrome in the United States is
34%.
7
The conversion rate from prediabetes to T2DM ranges
from 10% to 23% after 5 years and approximately 40% after 10
years,
8
which is five to seven times higher than in individuals
with normoglycemia. The 5-year conversion rate of metabolic
syndrome to T2DM is similarly five-fold.
9
In individuals with
both prediabetes and metabolic syndrome the risk of pro-
gression to T2DM is even higher.
9
Seventy-five percent of
those with prediabetes also have metabolic syndrome, and
individuals who meet diagnostic criteria for both prediabetes
and metabolic syndrome constitute the highest risk group for
T2DM.
9
Successful efforts to reduce or normalize the clinical
parameters used to define prediabetes and metabolic syn-
drome can lower the risk for T2DM.
4,10
Nutrition recom-
mendations for prevention of T2DM are available via the
Academy of Nutrition and Dietetics (the Academy) Evidence
Analysis Library (EAL) (www.andeal.org). Eleven of the
recommendations were developed from systematic reviews
of the literature. Two of the 11 recommendations received
the highest possible ratings that could be provided for
recommendations (strong). Additional information on the
development and rating of recommendations can be found
via the EAL. The two strong recommendations focus on
the effect of medical nutrition therapy (MNT) and weight
loss on clinical parameters used to define prediabetes
and metabolic syndrome. The purpose of this article is to
present the bases of the MNT and weight loss systematic
reviews upon which these two recommendations were
based.
METHODS
A detailed description of the methodology used for con-
ducting systematic reviews for the Academy EAL has been
published.
11
Methodology related to the systematic reviews
Table 1. National Cholesterol Education Program’s Adult Treatment Panel III (ATP III)
5
and World Health Organization (WHO)
6
definitions of metabolic syndrome
Risk factor
ATP III defining
level
a
WHO defining level
b
Abdominal obesity (cm)
Men >102
Women >88
Triglycerides (mmol/L)
c
1.7 1.7
High-density lipoprotein cholesterol (mmol/L)
d
Men <1.04 <0.9
Women <1.30 <1.0
Blood pressure (mm Hg) 130/85 140 systolic or 90 diastolic or taking
antihypertensive medication
Fasting glucose (mmol/L)
e
6.1
Insulin resistance Type 2 diabetes, impaired fasting glucose, impaired
glucose tolerance, or for those with normal
fasting glucose levels (<6.1 mmol/L), glucose
uptake below the lowest quartile for the
background population under investigation
under hyperinsulinemic, euglycemic conditions
Body mass index
f
>30
Waist-to-hip ratio
f
Men >0.9
Women >0.85
Urinary albumin excretion rate
g
(
m
g/min) 20
a
Must have three of the five risk factors for diagnosis.
b
Must have one item indicating insulin resistance and two of the other five risk factors for diagnosis.
c
To convert mmol/L triglycerides to mg/dL, multiply mmol/L by 88.6. To convert mg/dL triglycerides to mmol/L, multiply mg/dL by 0.0113. Triglycerides of 1.7 mmol/L¼150.6 mg/dL.
d
To convert mmol/L cholesterol to mg/dL, multiply mmol/L by 38.6. To convert mg/dL cholesterol to mmol/L, multiply mg/dL by 0.026. Cholesterol of 1.04 mmo/L¼40.14 mg/dL.
e
To convert mmol/L glucose to mg/dL, multiply mmol/L by 18.0. To convert mg/dL glucose to mmol/L, multiply mg/dL by 0.0555. Glucose of 6.1 mmol/L¼110 mg/dL.
f
Need to only meet body mass index or waist-to-hip ratio.
g
Or albumin-to-creatinine ratio 3.4 mg/mmol.
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Inclusion criteria Exclusion criteria
Population Individuals aged 18 y and older with
prediabetes (Academy of Nutrition and
Dietetics definition) or metabolic
syndrome (ATP III
a
or WHO
b
definition)
Individuals aged 18 y and older with
metabolic syndrome as defined by
WHO definition if diagnosis of
metabolic syndrome included
having type 2 diabetes
When the whole study sample did
not meet criteria for prediabetes or
metabolic syndrome, or when there
was no subsample meeting criteria
for prediabetes or metabolic
syndrome in which the outcomes
were reported on just the
subsample
Individuals aged 17 y and younger
Intervention Intervention criteria specific for each
question: medical nutrition therapy
and all methods of weight loss with at
least a 3-mo intervention
For medical nutrition therapy ques-
tion, for studies conducted in the
United States, when the dietary
intervention was not individualized
and delivered by a registered dietitian
nutritionist, it was not considered
medical nutrition therapy
For weight loss question, all
methods of weight loss with
<3-mo intervention
Comparison All types of interventions in which the
independent effect of the nutrition
therapy factor in question could be
determined
When the comparison intervention
changed components that would not
allow the independent effect of the
nutrition factor to be determined
Outcomes 2-h postprandial blood glucose
Glycated hemoglobin
Albumin-to-creatinine ratio
Fasting blood glucose
High-density lipoprotein
cholesterol
Systolic and diastolic blood
pressure
Urinary albumin excretion rate
Triglycerides
Waist circumference
Waist-to-hip ratio
Urinary albumin excretion rate and
albumin-to-creatinine ratio in individuals
with prediabetes
Study type Randomized controlled trial
Case control study
Cohort studies
Crossover studies
Nonrandomized clinical studies
Cross-sectional
Before-and-after studies
(continued on next page)
Figure 1. Inclusion and exclusion criteria for selected articles for medical nutrition therapy and weight loss questions for the
prevention of type 2 diabetes Academy of Nutrition and Dietetics (Academy) Evidence Analysis Library online entry using the
population, intervention, comparison, outcomes, and study type format.
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for the MNT and weight loss recommendations regarding the
prevention on T2DM are described in more detail below.
Committee
An expert workgroup was formed in 2008 to identify and
evaluate research to develop the Academy’s Prevention of
T2DM EAL online entry. The expert panel conducted their
work via conference calls, shared Internet workspace, and
two multiple-day workshops. The panel identified nutrition-
related intervention questions that addressed major nutrition
therapy factors, including MNT, weight loss, macronutrient
distribution, fiber intake, whole-grain intake, vegetable-
based protein consumed, type of fat consumed, fruit and
vegetable intake, sugar intake, glycemic index and glycemic
load of the diet, and physical activity related to the preven-
tion of T2DM in those at highest risk for T2DM, with highest
risk defined by Project IMAGE (Development and Imple-
mentation of a European Guideline and Training Standards
for Diabetes prevention).
3,12,13
Identification of Studies and Eligibility Criteria
For the recommendations on the EAL, a comprehensive
literature search was conducted using Medline, with searches
covering the time frame of 1995 to 2012 (before 1995 the
health conditions of prediabetes and metabolic syndrome
were not commonly recognized). However, for the weight
loss systematic review, July 2008 was used as earliest publi-
cation date in the search due to the inclusion of a Cochrane
Review on the topic of exercise or exercise and diet for
preventing T2DM.
14
The Cochrane Review, published in 2008,
includes landmark randomized controlled trials (RCTs) and
was included to represent these historical findings.
14
Only articles published in the English language were
considered for eligibility. Search terms included prediabetes,
pre-diabetes,impaired fasting glucose,borderline diabetes,
impaired glucose tolerance (prediabetes search terms); insulin
resistance syndrome,metabolic syndrome,dysmetabolic syn-
drome,syndrome X, and Reaven’s syndrome (metabolic syn-
drome search terms) combined with the nutrition factor of
interest. For MNT, search terms included medical nutrition
therapy,MNT,dietitian,dietician,nutritionist, and nutrition
professional. For weight loss, search terms included weight
management,weight loss,physical activity, and exercise.
Searches for prediabetes and metabolic syndrome were
conducted separately.
The abstracts of all studies identified by the search were
scanned by the workgroup members, and the full text of any
identified studies that were believed to have the potential to
meet inclusion criteria was retrieved for further evaluation.
Each retrieved article had a worksheet completed by an ev-
idence analyst who reported on methodologic quality, bias,
and outcomes of interest. Evidence analysts are members of
the Academy with an advanced degree and research experi-
ence. Before engaging in a systematic review for the EAL,
evidence analysts participate in a 2-day training program.
Worksheets completed by the evidence analysts were
reviewed by the work group members to further determine
whether the study met criteria for inclusion in the review.
Other studies included in the systematic reviews came from
Inclusion criteria Exclusion criteria
Publication date 1995 to November 2012
For weight loss question, July 2008
was used as earliest publication
date due to use of a Cochrane re-
view on the topic of exercise or
exercise and diet for preventing
type 2 diabetes
c
Earlier than 1995 and later than November
2012
Setting All settings
Sample size In randomized controlled trials, at least
10 participants per group
Samples <10 participants
Retention rate in follow-up >20%
Authorship If authors were on 2 or more articles,
when content appears different, then
all articles with different content are
included
If authors were on 2 or more articles, when
content appears similar, all earlier
articles (only the most recent article was
not excluded)
Language English
a
ATP III¼National Cholesterol Education Program’s Adult Treatment Panel III.
b
WHO¼World Health Organization.
c
The Cochrane Review includes weight loss interventions published before 2008, including the Diabetes Prevention Program.
Figure 1. (continued) Inclusion and exclusion criteria for selected articles for medical nutrition therapy and weight loss questions for
the prevention of type 2 diabetes Academy of Nutrition and Dietetics (Academy) Evidence Analysis Library online entry using the
population, intervention, comparison, outcomes, and study type format.
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Table 2. Included studies for medical nutrition therapy question in individuals with metabolic syndrome or prediabetes. All reported results are between-condition
analyses
Author(s), y, reference Sample
Study
design Intervention Cardiometabolic changes
Corpeleijn and
colleagues, 2006
15
N¼97
PreDM
a
RCT
b
Intervention: 12 mo
IG
c
Diet: Dutch guidelines, 55% kcal CHO
d
, 25%-30% kcal fat (<10%
kcal SFA
e
), <33 mg/MJ cholesterol
PA
f
: 30 min/d, 5 d/wk, supervised 1/wk
Deliverer: RD
g
, trainer
Contact: Every 3 mo, individual session
CG
h
Diet: No specific recommendations
PA: No specific recommendations
Deliverer: NR
i
Contact: 1, type of session NR
2-h PPG
j
(YIG vs CG) (P<0.01)
HbA1c
k
, FBG
l
,WC
m
(NS
n
)
DBP
o
, HDL
p
, SBP
q
,TG
r
, WHR
s
(NR)
Dyson and
colleagues,1997
16
N¼227
PreDM
RCT Intervention: 12 mo
IG
Diet: British Dietetic Association Guidelines,
500-700 kcal/d deficit when body mass index >22,
when body mass index <22 maintain weight
PA: 20-30 min, 5-6/wk
Deliverer: Fitness instructor, RD
Contact: Every 3 mo, individual session
Medication: Randomized to sulfonylureas or placebo/no drug
CG
Diet: Weight loss if body mass index >25, no specific
recommendations
PA: No specific recommendations
Deliverer: Physician
Contact: Every 3 mo, individual session
Medication: Randomized to sulfonylureas or placebo/no drug
2-h PPG, HbA1c, DBP, FBG, HDL,
SBP, TG, WHR (NS)
WC (NR)
(continued on next page)
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Table 2. Included studies for medical nutrition therapy question in individuals with metabolic syndrome or prediabetes. All reported results are between-condition
analyses (continued)
Author(s), y, reference Sample
Study
design Intervention Cardiometabolic changes
Eriksson and colleagues,
1999
17
N¼523
PreDM
RCT Intervention: 12 mo
IG
Diet: >50% kcal CHO, >20% kcal PUFA
t
/MUFA
u
or 25% kcal if
most came from MUFA, <10% kcal SFA, protein 1g/kg ideal
body weight, <300 mg cholesterol, 15 g fiber/1,000 kcal; at 6
mo when no weight loss and body mass index >30 then very
low calorie diet (6-12 wk)
PA: Promoted, 2/wk resistance training, supervised
Deliverer: RD
Contact: 7, individual session
CG
Diet: Reduce kcal (kcal NR) to achieve body mass index <25,
<30% kcal fat
PA: No specific recommendations
Deliverer: RD
Contact: 1, individual session
2-h PPG (YIG vs CG) (P<0.001)
DBP (YIG vs CG) (P<0.05)
FBG (YIG vs CG) (P<0.001)
TG (YIG vs CG) (P<0.001)
HDL, SBP, WC (NS)
HbA1c, WHR (NR)
Gagnon and colleagues,
2011
18
N¼48
PreDM
RCT Intervention: 12 mo
IG
Diet: No specific recommendations
PA: 60 min/d
Deliverer: Physician, RD, registered nurse
Contact: Every 6 wk, individual session; every 2 wk, group
session
CG
Diet: No specific recommendations
PA: 60 min/d
Deliverer: Physician, RD, registered nurse
Contact: Every 2 wk, group session
SBP (YIG vs CG) (P<0.03)
WC (YIG vs CG) (P<0.01)
2-h PPG, HbA1c, DBP, FBG, HDL,
TG (NS)
WHR (NR)
(continued on next page)
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Table 2. Included studies for medical nutrition therapy question in individuals with metabolic syndrome or prediabetes. All reported results are between-condition
analyses (continued)
Author(s), y, reference Sample
Study
design Intervention Cardiometabolic changes
Katula and colleagues,
2011
19
N¼301
PreDM
RCT Intervention: 12 mo
IG
Diet: 1,200-1,800 kcal/d
PA: 180 min/wk
Deliverer: CHW, RD
Contact: 1wk, group session for Mo 1-6; 3 individual sessions
for Mo 1-6; 1mo, group session for Mo 7-12; 1mo,
telephone call for Mo 7-12
CG
Diet: No specific recommendations
PA: No specific recommendations
Deliverer: RD
Contact: 2individual sessions for Mo 1-3, 1mo newsletter
FBG (YIG vs CG) (P<0.0001)
WC (YIG vs CG) (P<0.0001)
2-h PPG, HbA1c, DBP, HDL, SBP,
TG, WHR (NR)
Lindstrom and
colleagues, 2003
20
N¼522
PreDM
RCT Intervention: 24 mo
IG
Diet: 5% weight loss, 30% kcal fat (10% kcal SFA), 15 g/
1,000 kcal fiber
PA: 30 min/d
Deliverer: RD
Contact: 1, individual session
CG
Diet: No specific recommendations
PA: No specific recommendations
Deliverer: NR
Contact: 1, type of session NR
2-h PPG (YIG vs CG) (P¼0.0002)
HbA1c (YIG vs CG) (P¼0.0003)
DBP (YIG vs CG) (P¼0.0125)
FBG (YIG vs CG) (P<0.0001)
SBP (YIG vs CG) (P¼0.005)
TG (YIG vs CG) (P¼0.0026)
WC (YIG vs CG) (P¼0.0000)
HDL (NS)
WHR (NR)
(continued on next page)
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Table 2. Included studies for medical nutrition therapy question in individuals with metabolic syndrome or prediabetes. All reported results are between-condition
analyses (continued)
Author(s), y, reference Sample
Study
design Intervention Cardiometabolic changes
Mensink, Blaak, and
colleagues, 2003
21
N¼114
PreDM
RCT Intervention: 24 mo
IG
Diet: Dutch Guidelines for Healthy Eating, weight loss 5%-10%,
55% kcal CHO, 30%-35% kcal fat (<10% kcal SFA), 10%-15%
kcal protein, <33 mg/MJ cholesterol, 3 g/MJ fiber; low-energy
diet (kcal NR) provided as necessary during Mo 12-24
PA: 30 min/d, 5 d/wk
Deliverer: RD
Contact: 8, 3 individual session, other sessions NR
Medication: Diet agents (NR) provided as necessary during Mo
12-24
CG
Diet: No specific recommendations
PA: No specific recommendations
Deliverer: NR
Contact: 2, type of session NR
2-h PPG (YIG vs CG) (P<0.01)
TG (YIG vs CG) (P<0.01)
HbA1c, FBG, HDL, WHR (NS)
DBP, SBP, WC (NR)
Mensink, Feskens, and
colleagues, 2003
22
N¼102
PreDM
RCT Intervention: 12 mo
IG
Diet: Dutch Guidelines for Healthy Eating, weight loss 5%-10%,
55% kcal CHO, 30%-35% kcal fat (<10% kcal SFA), 10%-15%
kcal protein, <33 mg/MJ cholesterol, 3 g/MJ fiber
PA: 30 min/d, 5 d/wk
Deliverer: RD
Contact: 4, 1 group session, 3 individual session
CG
Diet: No specific recommendations
PA: No specific recommendations
Deliverer: NR
Contact: 1, type of session NR
2-h PPG (YIG vs CG) (P<0.05)
WC (YIG vs CG) (P<0.05)
HbA1c, FBG, WHR (NS)
DBP, HDL, SBP, TG (NR)
(continued on next page)
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Table 2. Included studies for medical nutrition therapy question in individuals with metabolic syndrome or prediabetes. All reported results are between-condition
analyses (continued)
Author(s), y, reference Sample
Study
design Intervention Cardiometabolic changes
Munakata and
colleagues, 2011
23
N¼109
MetS
v
RCT Intervention: 6 mo
Multiple guidance
Diet: 300-600 kcal/d deficit
PA: 30 min, 5/wk
Deliverer: Exercise trainer, physician, RD, registered nurse
Contact: Every 2 mo (when anthropometric change was not
achieved session was with exercise trainer, RD, physician, or
registered nurse; when anthropometric change was achieved
NR who contact was with), type of session NR
Single guidance
Diet: 300-600 kcal/d deficit
PA: 30 min, 5/wk
Deliverer: Exercise trainer, physician, RD, registered nurse
Contact: 1, type of session NR
FBG (YMultiple guidance vs
Single guidance) (P¼0.03)
WC (YMultiple guidance vs
Single guidance) (P¼0.02)
HbA1c, DBP, HDL, SBP, TG (NS)
2-h PPG, A:C, urinary albumin
excretion rate, WHR (NR)
Oldroyd and colleagues,
2001
24
N¼78
PreDM
RCT Intervention: 6 mo
IG
Diet: Nutrition Subcommittee British Diabetes Association,
reduce body mass index to <25, 55% kcal CHO, 30%-35% kcal
fat (PUFA:SFA ratio¼1.0), 20 g/1,000 kcal fiber
PA: 20-30 min, 2-3/wk
Deliverer: Physiotherapist, RD
Contact: 3bimonthly, 3monthly, individual session
CG
Diet: Maintain diet
PA: Maintain PA
Deliverer: None
Contact: None
DBP (YIG vs CG) (P¼0.05)
SBP (YIG vs CG) (P¼0.05)
2-h PPG, HbA1c, FBG, HDL, TG,
WC, WHR (NS)
(continued on next page)
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Table 2. Included studies for medical nutrition therapy question in individuals with metabolic syndrome or prediabetes. All reported results are between-condition
analyses (continued)
Author(s), y, reference Sample
Study
design Intervention Cardiometabolic changes
Oldroyd and colleagues,
2006
25
N¼78
PreDM
RCT Intervention: 24 mo
IG
Diet: Nutrition Subcommittee British Diabetes Association,
reduce body mass index to <25, 55% kcal CHO, 30%-35% kcal
fat (PUFA:SFA ratio¼1.0), 20 g/1,000 kcal fiber
PA: 20-30 min, 2-3x/wk
Deliverer: Physiotherapist, RD
Contact: 3bimonthly, 3monthly, 1at 9 mo, 5every
2 mo, individual session
CG
Diet: Maintain diet
PA: Maintain PA
Deliverer: None
Contact: None
2-h PPG, FBG, WC (NS)
HbA1c, DBP, HDL, SBP, TG, WHR
(NR)
a
PreDM¼prediabetes.
b
RCT¼randomized controlled trial.
c
IG¼intervention group.
d
CHO¼carbohydrate.
e
SFA¼saturated fatty acid.
f
PA¼physical activity.
g
RD¼registered dietitian or international equivalent.
h
CG¼control group.
i
NR¼not reported.
j
2-h PPG¼2-hour post prandial glucose.
k
HbA1c¼glycosylated hemoglobin.
l
FBG¼fasting blood glucose.
m
WC¼waist circumference.
n
NS¼not significant.
o
DBP¼diastolic blood pressure.
p
HDL¼high-density lipoprotein.
q
SBP¼systolic blood pressure.
r
TG¼triglycerides.
s
WHR¼waist-to-hip ratio.
t
PUFA¼polyunsaturated fatty acids.
u
MUFA¼monounsaturated fatty acids.
v
MetS¼metabolic syndrome.
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the other systematic reviews conducted for the project
(topics of systematic review included macronutrient distri-
bution, fiber intake, whole-grain intake, vegetable-based
protein consumed, type of fat consumed, fruit and vege-
table intake, sugar intake, glycemic index and glycemic load
of the diet, and physical activity) and other related EAL pro-
jects (eg, Diabetes 1 and 2 conducted by the Diabetes Work
Group).
Inclusion and Exclusion Criteria for Studies
Inclusion and exclusion criteria for studies were considered
apriori, using the population, intervention, comparison,
outcomes, and study type format (see Figure 1). To be
included in the review, studies had to include a sample of
adult participants, aged 18 years, not having T2DM but
considered to be at highest risk for T2DM, which were
those with prediabetes, as defined by the ADA (impaired
fasting glucose¼100 to125 mg/dL [5.55-6.94 mmol/L];
impaired glucose tolerance¼2-hour plasma glucose of 140
to 199 mg/dL [7.77-11.04 mmol/L]; or HbA1c¼5.7% to
6.4%),
4
and those with metabolic syndrome, using the Na-
tional Cholesterol Education Program’s Adult Treatment
Panel III
5
or WHO
6
definitions (see Table 1). For inclusion in
the review, the intervention had to be specificforthe
question, with MNT defined as individualized and delivered
by a registered dietitian nutritionist (RDN) (studies con-
ducted in the United States) or international equivalent,
and weight loss occurring over at least a 3-month period.
For studies with a comparison, all comparisons were
eligible, as long as the independent effect of MNT or weight
loss could be determined. To be included in the review,
studies needed to report on at least one outcome for pre-
diabetes in cases where the sample met prediabetes criteria
or one outcome for metabolic syndrome in cases where the
sample met metabolic syndrome criteria. For study design,
only those with higher quality were used, RCTs, case con-
trol, cohort, crossover, and nonrandomized trials were
included.
11
Data Extraction
The authors extracted data from the studies using several
steps. Author P.G.D. extracted information from the work-
sheets. To clarify data from the worksheets, P.G.D. went back
to the original article. If clarification was still required, au-
thors L.M. and H.A.R. also reviewed the original article.
Tables 2 and 3report on all studies included in the systematic
review for MNT and weight loss, respectively. Tables 2 and 3
include authors and year of publication, a description of the
sample (sample size and whether the sample was metabolic
syndrome or prediabetes), the study design, a description of
the intervention (eg, length, diet prescription, physical ac-
tivity prescription, who delivered the intervention, frequency
and type of contact during the intervention, and medication
when it was provided), and the cardiometabolic outcomes of
interest (2-hour postprandial blood glucose, HbA1c, albumin-
to-creatinine ratio, fasting blood glucose [FBG] level, high-
density lipoprotein cholesterol [HDL] level, systolic and
diastolic blood pressure, triglycerides [TG] level, urinary
albumin excretion rate, waist circumference [WC], and waist-
to-hip ratio [WHR]) collected at the last assessment point in
the investigation. For cardiometabolic outcomes, albumin-to-
creatinine ratio and urinary albumin excretion rate were not
reported when the sample was individuals with prediabetes
because these cardiometabolic measures are not considered
to be risk factors for prediabetes. For Table 3, weight loss was
also reported because this information assists in interpreting
the effect of the intervention (eg, weight loss) on the car-
diometabolic outcomes, and the time frame of weight loss is
the same time frame for the reported cardiometabolic out-
comes. For cardiometabolic outcomes and weight loss, when
significance was found in the investigation, it is reported in
Tables 2 and 3. The comparisons for significance depended on
the study design, with some studies reporting on within-
condition comparisons (ie, prospective cohorts), and other
studies reporting on between-condition comparisons (ie,
RCTs). The direction of significance is shown in Tables 2 and 3,
and when the comparison was between conditions, the
condition showing improvement in the outcome is indicated.
This review slightly differs from the EAL in that the review on
the EAL reports within-condition comparisons and between-
condition comparisons regardless of type of study.
Outcomes of Interest
The primary end points of the reviews were the clinical pa-
rameters used to diagnose prediabetes and metabolic syn-
drome because improvements in these parameters would
lower the risk for developing T2DM.
4,10
Although body mass
index is a clinical parameter to diagnose metabolic syndrome
using the WHO definition,
6
it was not included as an outcome
of interest because it is actually an outcome of the efficacy of
the weight loss intervention for the weight loss question. The
clinical parameters reported are those collected at the final
assessment in the investigation. Incidence of T2DM was not
an outcome evaluated.
RESULTS
MNT Provided by an RDN
The initial search yielded eight abstracts, and an additional 23
abstracts were identified from systematic searches for the
other questions included on the EAL and from the Diabetes
Work Group, providing 31 abstracts. From the abstract re-
view, all 31 articles were pulled to review, and 11 publica-
tions were included in the review (see Figure 2).
Results of the review for MNT are shown in Table 2. For
MNT, 11 publications were identified, with all studies being
RCTs.
15-25
One publication met the inclusion criteria for
metabolic syndrome,
23
and 10 of the publications met the
prediabetes inclusion criteria.
15-22,24,25
All of the studies had a
condition that provided MNT that was delivered by an RDN or
international equivalent. The MNT interventions ranged in
length from 6 to 24 months, with MNT delivered via indi-
vidual and/or group sessions in differing amounts of contact.
The dietary interventions provided in the MNT conditions
varied, but the majority of the publications, nine, included a
weight loss focus within the dietary intervention.
16,17,19-25
All
MNT interventions included a physical activity goal. Two
MNT interventions included medication.
16,21
All but two
comparison conditions to the MNT conditions had less con-
tact with providers.
16,20
The comparison conditions in all
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Aizawa and
colleagues,
2009
26
N¼34
MetS
a
PC
b
Intervention: 24 wk
Diet: Mediterranean-style, based
on stage of change, with 5
provided dinner meals
PA
c
: Aerobic exercise prescription
based on stage of change
Deliverer: FP
d
Contact: 1wk, individual session
2.3 kg (P<0.05) YDBP
e
, FBG
f
, SBP
g
,WC
h
(P<0.05)
HDL
i
,TG
j
(NS
k
)
2-h PPG
l
, HbA1c
m
, A:C
n
, UAER
o
,
WHR
p
(NR
q
)
Allen and
colleagues,
2008
27
N¼42
PreDM
r
PC
Participants were
randomized to
Lifestyle or Control,
but outcomes are
reported as 1
cohort
Intervention: 6 mo, with 18 mo
follow-up
Lifestyle
Diet: Healthy lifestyle
PA: No specific recommendations
Deliverer: NR
Contact: 1mo, group session
Control
Diet: None
PA: None
Deliverer: None
Contact: None
0.5 kg (NS) YFBG (P<0.001)
DBP, HDL, SBP, TG, WC (NS)
2-h PPG, HbA1c, WHR (NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Al-Sarraj and
colleagues,
2010
28
N¼39
MetS
RCT
s
Intervention: 12 wk
Caloric restriction
Diet: Calorie-restricted diet (20%-
25% kcal CHO
t
, 45%-50% kcal
fat, 25%-30% kcal protein)
PA: Instructed not to change
Deliverer: RD
u
Contact: Every 2 wk, individual
session
American Heart Association
Diet: Calorie-restricted diet for 6
wk, American Heart Association
diet (55% kcal CHO, <30% kcal
fat, 15%-20% kcal protein) for 6
wk
PA: Instructed not to change
Deliverer: RD
Contact: Every 2 wk, individual
session
8.4% Caloric restriction vs
e5.6% American Heart
Association (P<0.01)
v
TG (YCaloric restriction vs
American Heart Association)
(P<0.001)
HDL (NS)
2-h PPG, HbA1c, A:C, DBP, FBG,
SBP, UAER, WC, WHR (NR)
Bihan et al,
2009
29
N¼95
MetS
PC
Some outcomes
reported by sex,
some outcomes
reported as the
whole sample
Intervention: 6 mo
Diet: French diet
recommendations
PA: French PA recommendations
Deliverer: General practitioner
physician
Contact: 2over 6 mo, individual
session
1.1 kg Women (SNR
w
)
1.7 kg Men (SNR)
YHDL (Women; P¼0.022)
(Men; P¼0.048)
YWC (Women; P¼0.004) (Men;
P¼0.000)
YDBP, SBP, TG (P¼0.000)
FBG (NS)
2-h PPG, HbA1c, A:C, UAER, WHR
(NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Burtscher and
colleagues,
2009
30
N¼36
PreDM
RCT Intervention: 12 mo
Counseling
Diet: Hypocaloric (kcal NR), <30%
kcal fat, <10% SFA
x
PA: 30 min/d
Deliverer: Health promotion and
exercise physiology specialists
Contact: 1, type of session NR
CounselingþSupervised exercise
Diet: Hypocaloric (kcal NR), <30%
kcal fat, <10% SFA
PA: 30 min/d þsupervised exercise
1h,2wk
Deliverer: Health promotion and
exercise physiology specialists,
sport scientist
Contact: 1, type of session NR; 1
mo diet review, type of session
NR
þ1.0% Counseling vs e3.0%
CounselingþSupervised
exercise (P<0.03)
v
DBP, FBG, HDL, SBP (NS)
2-h PPG, HbA1c, TG, WC, WHR (NR)
Busnello and
colleagues,
2011
31
N¼82
MetS
RCT Intervention: 4 mo
Intervention group
Diet: Brazilian Guidelines for MetS
PA: No specific recommendations
Deliverer: NR
Contact: 1mo, type of session NR
Control group
Diet: Brazilian Guidelines for MetS
PA: No specific recommendations
Deliverer: NR
Contact: 1, type of session NR
1.2 kg Intervention group vs
e1.9 kg Control group (NS)
FBG, HDL, TG, WC, WHR (NS)
2-h PPG, HbA1c, A:C, DBP, SBP,
UAER (NR)
Caiazzo and
colleagues,
2010
32
N¼53
PreDM
PC 5 y follow-up following
laparoscopic adjustable gastric
banding
26% (P<0.05)
v
Y2-h PPG, HbA1c, FBG, SBP, TG
(P<0.05)
[HDL (P<0.05)
DBP, WC, WHR (NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Chan and
colleagues,
2008
33
N¼35
MetS
RCT Intervention: 16 wk
Intervention group
Diet: Hypocaloric diet (kcal NR) (14
wk): Stabilization diet (2 wk)
PA: Instructed not to change
Deliverer: NR
Contact: Every 3 wk, type of
session NR
Control group
Diet: Isocaloric weight
maintenance (kcal NR)
PA: Instructed not to change
Deliverer: NR
Contact: Every 3 wk, type of
session NR
13 kg Intervention group
vs þ4 kg Control group
(P<0.001)
TG (YIntervention group vs Control
group) (P<0.05)
WC (YIntervention group vs
Control group) (P<0.001)
FBG, HDL (NS)
2-h PPG, HbA1c, A:C, DBP, SBP,
UAER, WHR (NR)
Christian and
colleagues,
2011
34
N¼279
MetS
RCT Intervention: 6 mo
Intervention group
Diet: Computer-generated
individualized prescription for
weight loss
PA: Computer-generated
individualized prescription for
weight loss
Deliverer: Physician
Contact: 2over 6 mo, individual
session
Control group
Diet: Standard care
PA: Standard care
Deliverer: Physician
Contact: Standard care
1.50 kg Intervention group
vs þ0.15 kg Control group
(P¼0.002)
WC (YIntervention group vs
Control group) (P¼0.01)
DBP, FBG, HDL, SBP, TG (NS)
2-h PPG, HbA1c, A:C, UAER, WHR
(NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Cicero and
colleagues,
2009
35
N¼28
MetS
NRT
y
Intervention: 202 d
Sequential intervention
Phase 1: Diet
Diet: American Heart Association
Step 2, with 600 kcal/d deficit
(3 mo)
PA: NR
Deliver: NR
Contact: Number and type of
session NR
Phase 2: Moderate exercise
Diet: NR
PA: Moderate level (5 d/wk)
for 56 d
Deliverer: NR
Contact: Number and type of
session NR
Phase 3: Intense exercise
Diet: NR
PA: Intense level (5 d/wk) for 56 d
Deliverer: NR
Contact: Number and type of
session NR
0.9 kg Moderate exercies vs
2.0 kg Intensive exercise
(NS)
HDL ([Moderate exercise,
Intensive exercise vs Diet)
(P<0.001)
TG (YModerate exercise, Intensive
exercise vs Diet) (P¼0.001)
2-h PPG, HbA1c, A:C, DBP, FBG,
SBP, UAER, WC, WHR (NR)
de la Cruz-
Munoz and
colleagues,
2011
36
N¼276
PreDM
RC
z
(within condition) 3-y follow-up following
laparoscopic adjustable gastric
banding, Roux-en-Y
47 kg (SNR) YHbA1c, FBG (SNR)
2-h PPG, DBP, HDL, SBP, TG WC,
WHR (NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Gagnon and
colleagues,
2011
18
N¼48
PreDM
RCT Intervention: 12 mo
Intervention group
Diet: No specific recommendations
PA: 60 min/d
Deliverer: Physician, RD, registered
nurse
Contact: Every 6 wk, individual
session; every 2 wk, group
session
Control group
Diet: No specific recommendations
PA: 60 min/d
Deliverer: Physician, RD, registered
nurse
Contact: Every 2 wk, group session
4.9 kg Intervention group vs
0.6 kg Control group
(P<0.01)
SBP (YIntervention group vs
Control group) (P<0.03)
WC (YIntervention group vs
Control group) (P<0.01)
2-h PPG, HbA1c, DBP, FBG, HDL, TG
(NS)
WHR (NR)
Katula and
colleagues
2011
19
N¼301
PreDM
RCT Intervention: 12 mo
Intervention group
Diet: 1,200-1,800 kcal/d
PA: 180 min/wk
Deliverer: Community health
worker, RD
Contact: 1wk, group session for
Mo 1-6; 3 individual sessions for
Mo 1-6; 1mo, group session
for Mo 7-12; 1mo, telephone
call for Mo 7-12
Control group
Diet: No specific recommendations
PA: No specific recommendations
Deliverer: RD
Contact: 2individual sessions for
Mo 1-3, 1mo newsletter
6.97 kg Intervention group vs
1.74 Control group
(P<0.0001)
FBG (YIntervention group vs
Control group) (P<0.0001)
WC (YIntervention group vs
Control group) (P<0.0001)
2-h PPG, HbA1c, DBP, HDL, SBP, TG,
WHR (NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Kim and
colleagues,
2009
37
N¼20
MetS
NRT
aa
A non-MetS condition
was included in the
trial but is not
reported
Intervention: 12 wk
Diet: Instructed not to change
PA: 60 min/d, 3 d/wk, supervised
Deliverer: Exercise physiologist
Contact: 3wk, type of session NR
3.0 kg (NS) YHbA1c, TG, WC (P<0.01)
DBP, FBG, HDL, SBP (NS)
2-h PPG, A:C, UAER, WHR (NR)
Lee and
colleagues,
2009
38
N¼75
MetS
RCT Intervention: 12 wk
High protein
Diet: Meal replacement diet (low-
kcal [1,200-1,500 kcal/d], 2 meal
replacements/d), 50% kcal CHO,
20% kcal fat, 30% kcal protein;
25 g fiber
PA: Promoted
Deliverer: RD, registered nurse
Contact: 5individual telephone
session, 5in-person, type of
session NR
Control protein
Diet: Meal replacement diet (low-
kcal [1,200-1,500 kcal/d], 2 meal
replacements/d), 65% kcal CHO,
20% kcal fat, 15% kcal protein 25
gfiber
PA: Promoted
Deliverer: RD, registered nurse
Contact: 5individual telephone
session, 5in-person, type of
session NR
5.0 kg High protein vs 4.9 kg
Control protein (NS)
DBP, FBG, HDL, SBP, TG, WC (NS)
2-h PPG, HbA1c, A:C, UAER, WHR
(NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Lu and
colleagues,
2011
39
N¼210
PreDM
RCT Intervention: 24 mo
Intervention group
Diet: No specific recommendations
PA: No specific recommendations
Deliverer: NR
Contact: Every 3 mo lifestyle group
session; 1mo individual
telephone contact
Medication: Acrabose or
metformin
Control group
Diet: Standard care
PA: Standard care
Deliverer: NR
Contact: Standard care
Medication: Standard care
2.66 kg Intervention group vs
e1.48 Control group
(P¼0.013)
2-h PPG (YIntervention group vs
Control group) (P¼0.032) DBP
(YIntervention group vs Control
group) (P<0.0000)
FBG (YIntervention group vs
Control group) (P¼0.046) SBP
(YIntervention group vs Control
group) (P<0.0000)
TG (YIntervention group vs Control
group) (P¼0.038)
WC (YIntervention group vs
Control group) (P¼0.019)
HbA1c, HDL (NS)
WHR (NR)
Mujica and
colleagues
2010
40
N¼51
MetS
RCT Intervention: 18 wk
Intervention group
Diet: No specific recommendations
PA: 60 min 3/wk, supervised
Deliverer: Physician, psychologist,
physical therapist, RD
Contact: 1mo over 4 mo, group
session
Control group
Diet: None
PA: None
Deliverer: None
Contact: None
3.9 kg Intervention group vs
e0.7 kg Control group
(P¼0.012)
DBP (YIntervention group vs
Control group) (P¼0.014)
TG (YIntervention group vs Control
group) (P<0.001)
WC (YIntervention group vs
Control group) (P<0.001)
FBG, HDL, SBP (NS)
2-h PPG, HbA1c, A:C, UAER, WHR
(NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Munakata and
colleagues
2011
23
N¼109
MetS
RCT Intervention: 6 mo
Multiple guidance
Diet: 300-600 kcal/d deficit
PA: 30 min, 5/wk
Deliverer: Exercise trainer,
physician, RD, registered nurse
Contact: Every 2 mo (in case
anthropometric change was not
achieved session was with
exercise trainer, RD, physician, or
registered nurse; in case
anthropometric change was
achieved, NR who contact was
with), type of session NR
Single guidance
Diet: 300-600 kcal/d deficit
PA: 30 min, 5/wk
Deliverer: Exercise trainer,
Physician, RD, registered nurse
Contact: 1, type of session NR
4.1 kg Multiple guidance vs
e2.5 kg Single guidance (NS)
FBG (YMultiple guidance vs Single
guidance) (P¼0.03)
WC (YMultiple guidance vs Single
guidance) (P¼0.02)
HbA1c, DBP, HDL, SBP, TG (NS)
2-h PPG, A:C, UAER, WHR (NR)
Ng and
colleagues
2009
41
N¼35
MetS
RCT Intervention: 16 wk
Intervention group
Diet: Hypocaloric (kcal NR), low-fat
(amount of fat NR) diet (14 wk);
maintenance diet (NR) (2 wk)
PA: Instructed not to change
Deliverer: NR
Contact: NR
Control group
Diet: Isocaloric weight
maintenance (kcal NR)
PA: Instructed not to change
Deliverer: NR
Contact: NR
13 kg Intervention group
vs þ4 kg Control group
(P<0.001)
TG (YIntervention group vs Control
group) (P<0.05)
WC (YIntervention group vs
Control group) (P<0.001)
FBG, HDL (NS)
2-h PPG, HbA1c, A:C, DBP, SBP,
UAER, WHR (NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Oh and
colleagues
2010
42
N¼52
MetS
RCT Intervention: 6 mo, 12 mo
follow-up
Intervention group
Diet: <1,500 kcal/d, 55%-60% kcal
CHO
PA: 3 supervised sessions/wk, Mo
1-3; 2 supervised sessions/wk,
Mo 4-6
Deliverer: Exercise physiologist,
nurse practitioner
Contact: 90 min each session for
diet and PA, group session
Control group
Diet: General written education
PA: General written education
Deliverer: NR
Contact: None
4.3 kg Intervention group vs
e0.9 kg Control group
(P<0.001)
WC (YIntervention group vs
Control group) (P<0.001)
DBP, FBG, HDL, SBP, TG (NS)
2-h PPG, HbA1c, A:C, UAER, WHR
(NR)
Orozco and
colleagues,
2008
14
N¼8 studies
in 25
publications
Participants at
high risk for
development
of type 2
diabetes
bb
Meta-analysis RCTs of exercise and diet
interventions of a minimum of 6
mo duration and a comparison
of a standard recommendation
arm, reporting on diabetes
incidence
Pooled effect of intervention
eY2.72 kg (95% CI)
Pooled effect of intervention:
YDBP (95% CI)
YFBG (95% CI)
YSBP (95% CI)
YTG (95% CI)
YWC (95% CI)
2-h PPG, WHR (NS)
HDL (not estimable)
A1c, A:C, UAER (NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Parikh and
colleagues,
2010
43
N¼99
PreDM
RCT Intervention: 10 wk, 12 mo follow-
up
Intervention group
Diet: No specific recommendations
PA: No specific recommendations
Deliverer: Peer leaders
Contact: 8 sessions, group session
Control group
Diet: None
PA: None
Deliverer: None
Contact: None
3.3 kg Intervention group vs
e1.1 Control group (P<0.01)
YWC (Intervention group vs
Control group) (P¼0.05)
2-h PPG, HbA1c, DBP, FBG, SBP
(NS)
HDL, TG, WHR (NR)
Sakane and
colleagues,
2011
44
N¼304
PreDM
RCT Intervention: 36 mo
Intervention group
Diet: <25% kcal fat, <160 kcal/d
from alcohol, 3 meals/d, avoid
eating late at night
PA: 700 kcal/wk
Deliverer: NP
Contact: 4during Mo 1-6, group
session; 2year, individual
session
Control group
Diet: No specific recommendations
PA: No specific recommendations
Deliverer: Nurse practitioner
Contact: 1, group session
1.8 kg Intervention group vs
1.5 kg Control group (NS)
2-h PPG, FBG, WC (NS)
HbA1c, DBP, HDL, SBP, TG, WHR
(NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Seligman and
colleagues
2011
45
N¼75
MetS
RCT Intervention: 12 wk
Healthy diet
Diet: Healthy diet guidance
PA: 10,000 steps/d
Deliverer: NR
Contact: NR
Healthy dietþPA
Diet: Healthy diet guidance
PA: 45 min 3/wk cyclergometer,
60 min brisk walking on other
days
Deliverer: NR
Contact: NR
Control
Diet: 30 kcal/kg body weight, 50%
to 65% kcal from CHO, 20% kcal
from fat (7%-8% kcal from SFA),
15%-20% kcal from protein
PA:1 h/d walking
Deliverer: NR
Contact: NR
9.0 kg Healthy diet vs
11.0 kg Healthy dietþPA vs
e8.0 kg Control (NS)
HDL ([Healthy dietþPA vs Control)
(P¼0.028)
UAER (YHealthy dietþPA vs
Control) (P¼0.05)
DBP, SBP, TG, WC (NS)
2-h PPG, HbA1c, A:C, FBG, WHR
(NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Straznicky and
colleagues
2011
46
N¼38
MetS
RCT Intervention: 12 wk
Weight loss
Diet: Modified Dietary Approaches
to Stop Hypertension diet, 600
kcal/d deficit, 22% kcal protein
PA: No specific recommendations
Deliverer: NR
Contact: NR
Weight lossþexercise
Diet: Modified Dietary Approaches
to Stop Hypertension diet, 600
kcal/d deficit, 22% kcal protein
PA: 40-min cycling 3-4 d/wk and
1wk supervised
Deliverer: NR
Contact: NR
Control
Diet: No specific recommendations
PA: No specific recommendations
Deliver: None
Contact: None
7.9 kg Weight loss and
10.4 kg Weight lossþ
exercise vs þ1.4 kg Control
(P<0.01)
e7.9 kg Weight loss vs
e10.4 kg Weight lossþ
exercise (P<0.05)
FBG (Yboth weight loss groups vs
Control) (P<0.001)
SBP (YWeight lossþexercise vs
Control) (P<0.01)
TG (YWeight lossþexercise vs
Control) (P<0.001)
WC (Yboth weight loss groups vs
Control) (P<0.001)
WC (YWeight lossþexercise vs
weight loss) (P<0.01)
2-h PPG, A:C, DBP, HDL, WHR (NS)
HbA1c, UAER (NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Straznicky and
colleagues,
2012
47
N¼63
MetS
RCT Intervention: 12 wk
Weight loss
Diet: Modified Dietary Approaches
to Stop Hypertension diet, 600
kcal/d deficit, 48% kcal CHO,
30% kcal fat (9% kcal SFA), 22%
kcal protein
PA: No specific recommendations
Deliverer: Nutritionist
Contact: Every 2 wk, type of
session NR
Weight lossþexercise
Diet: Modified Dietary Approaches
to Stop Hypertension diet, 600
kcal/d deficit, 48% kcal CHO,
30% kcal fat (9% kcal SFA), 22%
kcal protein
PA: 40-min cycling 3-4 d/wk and
1wk supervised
Deliverer: Nutritionist
Contact: Every 2 wk, type of
session NR
Control
Diet: Usual diet
PA: Usual activity
Deliver: None
Contact: None
7.1 kg Weight loss and 8.7 kg
Weight lossþexercise
vs þ1.0 kg Control (P<0.01)
FBG (Yboth weight loss groups vs
Control) (P<0.01)
TG (Yboth weight loss groups vs
Control) (P<0.01)
WC (Yboth weight loss groups vs
Control) (P<0.01)
WC (YWeight lossþexercise vs
Weight loss) (P<0.05)
WHR (YWeight lossþexercise vs
Control) (P<0.01)
DBP, HDL, SBP (NS)
2-h PPG, HbA1c, A:C, UAER (NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Straznicky and
colleagues
2010
48
N¼59
MetS
RCT Intervention: 12 wk
Weight loss
Diet: Modified Dietary Approaches
to Stop Hypertension diet, 600
kcal/d deficit, 48% kcal CHO,
30% kcal fat (15% kcal MUFA
cc
,
6% kcal Ppolyunsaturated fatty
acids, 9% kcal SFA), 22% kcal
protein
PA: No specific recommendations
Deliverer: NR
Contact: NR
Weight lossþexercise
Diet: Modified Dietary Approaches
to Stop Hypertension diet, 600
kcal/d deficit, 48% kcal CHO,
30% kcal fat (15% kcal MUFA, 6%
kcal polyunsaturated fatty acids,
9% kcal SFA), 22% kcal protein
PA: 40-min cycling 3-4 d/wk and
1wk supervised
Deliverer: NR
Contact: NR
Control
Diet: Usual diet
PA: Usual activity
Deliver: None
Contact: None
7.1 kg Weight loss and
8.4 kg Weight lossþexercise
vs þ1.0 kg Control (P<0.01)
FBG (Yboth weight loss groups vs
Control) (P<0.05)
TG (Yboth weight loss groups vs
Control) (P<0.05)
WC (Yboth weight loss groups vs
Control) (P<0.01)
WC (YWeight lossþexercise vs
weight loss) (P<0.01)
WHR (YWeight lossþexercise vs
Control) (P<0.01)
2-h PPG, DBP, HDL, SBP, DBP (NS)
HbA1c, A:C, UAER (NR)
(continued on next page)
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Table 3. Included studies for weight loss question in individuals with metabolic syndrome or prediabetes (continued)
Author(s), y,
reference Sample Study design Intervention Weight loss Cardiometabolic outcomes
Yassine and
colleagues,
2009
49
N¼24
MetS
RCT Intervention: 12 wk
Exercise
Diet: No specific recommendations
PA: 50-60 min, 5/wk supervised
Deliverer: Exercise physiologist
Contact: 5wk, type of session NR
Exerciseþcaloric restriction
Diet: 500 kcal/d deficit
PA: 50-60 min, 5/wk supervised
Deliverer: RD, exercise physiologist
Contact: 1wk with RD, type of
session NR; 5wk with exercise
physiologist, type of session NR
3.8 kg Exercise vs 6.9 kg
Exerciseþcaloric restriction
(P¼0.02)
2-h PPG, DBP, FBG, HDL, SBP, TG,
WC, WHR (NS)
HbA1c, A:C, UAER (NR)
a
MetS¼metabolic syndrome.
b
PC¼prospective cohortewithin-condition analysis.
c
PA¼physical activity.
d
FP¼family physician.
e
DBP¼diastolic blood pressure.
f
FBG¼fasting blood glucose.
g
SBP¼systolic blood pressure.
h
WC¼waist circumference.
i
HDL¼high-density lipoprotein cholesterol.
j
TG¼triglycerides.
k
NS¼not significant.
l
2-h PPG¼2-hour postprandial glucose.
m
HbA1c¼glycosylated hemoglobin.
n
A:C¼albumin creatinine ratio.
o
UAER¼urinary albumin excretion rate.
p
WHR¼waist-to-hip ratio.
q
NR¼not reported.
r
PreDM¼prediabetes.
s
RCT¼randomized controlled trialebetween-condition analysis.
t
CHO¼carbohydrate.
u
RD¼registered dietitian nutritionist or international equivalent.
v
Weight change only reported in % weight loss.
w
SNR¼significance not reported.
x
SFA¼saturated fatty acids.
y
NRT¼nonrandomized trial-between-condition analysis.
z
RC¼retrospective cohort-within-condition analysis.
aa
NRT¼nonrandomized trial-within-condition analysis.
bb
Impaired glucose tolerance according to the World Health Organization criteria, impaired fasting glucose according to the American Diabetes Association criteria, previous gestational diabetes, hypertension 140/90 mm Hg, family history of type 2
diabetes in first-degree relatives, obesity (ie, body mass index 30), dyslipidemia (ie, HDL cholesterol 35 mg/dL [0.91 mmol/L], triglycerides 250 mg/dL [2.82 mmol/L], or both), or high-risk ethnic groups (eg, African-Americans, Hispanic-
Americans, native Americans, Asian-Americans, and Pacific Islanders).
cc
MUFA¼monounsaturated fatty acid.
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publications, except for two publications,
18,23
provided much
less guidance, and often no specific recommendations, on
diet and/or physical activity. No publication compared the
same intervention delivered by an RDN or international
equivalent vs another provider.
All 11 publications reported on glycemic outcomes,
15-25
with four of 11 publications demonstrating significant de-
creases in FBG in the MNT vs comparison condition.
17,19,20,23
Nine of the publications reported 2-hour postprandial blood
glucose levels,
15-18,20-22,24,25
with five reporting significant
decreases in MNT vs the comparison condition.
15,17,20-22
Eight
publications reported HbA1c,
15,16,18,20-24
with only one
reporting significant decreases in MNT vs the comparison
condition.
20
Thus, seven of 11 publications reported on a
significant reduction in a glycemic outcome in the MNT vs a
comparison condition.
Seven publications reported on lipid levels.
16-18,20,21,23,24
For TG, three
17,20,21
out of seven
16-18,20,21,23,24
publications
found a significant decrease in MNT vs the comparison con-
dition.
16-18,20,21,23,24
Seven publications reported on change in
HDL, with no publication reporting significant condition dif-
ferences.
16-18,20,21,23,24
Thus, three of seven publications on
lipids reported a significant reduction in the MNT vs a com-
parison condition.
Eleven publications examined changes in anthropometric
characteristics,
15-25
with five
18-20,22,23
out of nine
15,17-20,22-25
publications reporting a significant decrease in WC in MNT
vs the comparison condition, with four publications reporting
no condition difference in WHR,
16,21,22,24
leaving five out of 11
publications reporting a significant decrease in anthropo-
metric characteristics in MNT vs the comparison condition.
Out of six publications
16-18,20,23,24
reporting blood pressure,
three reported significant reductions in systolic blood pres-
sure in the MNT vs the comparison condition,
18,20,24
and
three reported significant reductions in diastolic blood pres-
sure in the MNT vs comparison condition,
17,20,24
resulting in
Abstracts Retrieved=31
Screened=31
Full-text articles assessed for
eligibility=31
Full-text articles excluded=20
•Not meeting MNT
definition=13
•Incorrect sample=6
•Retention at follow-up too
low=1
Included=11
PubMed=8
Abstracts from other questions
and from Diabetes Work
Group=23
Figure 2. Diagram of process of selecting included studies for medical nutrition therapy (MNT) question.
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four out of six publications reporting on decreases in blood
pressure in the MNT vs the comparison condition. There were
no studies identified for MNT that reported on renal out-
comes in individuals with metabolic syndrome.
Two publications tested two versions of MNT, with the only
condition difference being frequency of contact.
18,23
These
studies did find that the condition with greater frequency of
contact had significantly greater decreases in FBG, systolic
blood pressure, and WC.
18,23
Weight Loss
The initial search yielded 476 abstracts. From the abstract
review, 176 articles were pulled to review, and 28 publica-
tions were included in the review (see Figure 3).
Results for the review on weight loss are shown in Table 3.
For weight loss, 28 publications
14,18,19,23,26-49
were identified,
with 20 being RCTs,
18,19,23,28,30,31,33,34,38-49
five being cohort
studies,
26,27,29,32,36
two publications were nonrandomized
trials,
35,37
and one publication was a meta-analysis of RCTs
that included 25 publications.
14
Eighteen publications met
the metabolic syndrome inclusion criteria
23,26,28,29,31,
33-35,37,38,40-42,45-49
and 10 publications met the criteria for
prediabetes.
14,18,19,27,30,32,36,39,43,44
Two of 28 publications re-
ported on follow-up after bariatric surgery,
32,36
whereas the
remaining publications reported on nonbariatric weight
loss interventions. One publication included medication in
the weight loss intervention.
39
The weight loss in-
terventions ranged in length from 3 months to 5 years, with
the longest interventions being bariatric interventions. For
nonbariatric interventions, interventions were delivered via
individual and/or group sessions in differing amounts of
contact by one or multiple providers, with providers rep-
resenting several disciplines. The dietary and physical
activity interventions provided to the condition(s) consid-
ered to be helpful for weight loss varied widely, with all
but one publication providing some dietary information
Abstracts Retrieved=476
Screened=476
Records Excluded=300
Full-text articles assessed for
eligibility=176
Full-text articles excluded=148
•Incorrect sample=44
•No reported weight loss or
intervention=25
•Intervention less than 3
months=20
•Incorrect study design=10
•Sample size too small=14
•Retention at follow-up too
low=13
•Other eligibility issues=22
Included=28
PubMed=476
Figure 3. Diagram of process of selecting included studies for the weight loss question.
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(ie, participants were asked to not change dietary intake),
37
and all but four publications providing some physical ac-
tivity information (ie, three publications asked participants
to not change physical activity
28,33,41
and one publication
did not report any information about what was provided to
participants on physical activity
35
). The meta-analysis
examined diet and physical activity interventions that
were at least 6 months long.
14
The comparison conditions varied tremendously in the
RCTs and nonrandomized trials.
18,19,23,28,30,31,33-35,38-49
In 10
of these publications, there included a comparison condition
that provided less dietary and physical activity information
and contact than an intervention designed for weight
loss.
19,34,39,40,42-44,46-48
In three of these publications a com-
parison condition had less contact, but provided equal di-
etary and physical activity information than an intervention
designed for weight loss.
18,23,31
In three of these publications,
a comparison condition had identical contact and physical
activity information but different dietary information than an
intervention designed for weight loss,
28,33,38
and in three of
these publications a comparison condition had identical
contact and dietary information but different physical
activity information than an intervention designed for weight
loss.
46-48
One publication had a comparison condition with
identical physical activity information and different dietary
information and frequency of contact than an intervention
designed for weight loss.
49
One publication had a comparison
condition with identical dietary information and different
physical activity information and frequency of contact than
an intervention designed for weight loss.
30
Three publica-
tions did not report on dietary information, physical activity
information, or frequency of contact.
35,41,45
The meta-analysis
examined comparison conditions composed of standard
recommendations.
14
Eighteen publications reported on significant within- (for
studies analyzed as cohort studies)
26,32
or between- (for
trials)
14,18,19,28,30,33,34,39-43,46-49
condition weight loss out-
comes. For significant weight loss outcomes, weight changes
ranged from e1.5 t o e13.0 kg and e3.0% to e26% weight loss.
The meta-analyses reported a statistically significant pooled
effect of e2.72 kg.
14
The largest kilogram amount of signifi-
cant weight loss was from a 16-week intervention that
included a hypocaloric diet (kilocalorie amount was not re-
ported) and instructions for participants not to change
physical activity, with contact occurring every 3 weeks (type
of contact and who provided the contact was not reported),
33
whereas the largest significant percent weight loss occurred
5 years after laparoscopic adjustable gastric banding.
32
Twenty-five publications, including the meta-analysis,
14
reported on glycemic outcomes.
14,18,19,23,26,27,29-34,36-44,46-49
For FBG, 10
14,19,23,26,27,32,39,46-48
out of 25
14,18,19,23,26,27,29-34,
36-44,46-49
publications, including the meta-analysis,
14
reported
significant within- or between-condition decreases in FBG.
Of 10 publications reporting significant FBG out-
comes,
14,19,23,26,27,32,39,46-48
eight, including the meta-
analysis,
14
also reported within- or between-condition
significant weight loss.
14,19,26,32,39,46-48
Nine publications,
including the meta-analysis,
14
reported on 2-hour post-
prandial glucose,
14,18,32,39,43,44,46,48,49
with two reporting
significant within- or between-condition decreases, as well
as significant weight loss.
32,39
For HbA1c, six publications
reported on outcomes,
18,23,32,37,39,43
with two finding within-
condition significant reductions,
32,37
and of these two, one
also found within-condition significant weight loss.
32
Thus,
out of 25 publications, 11, one being a meta-analysis, found
significant reductions in at least one glycemic outcome and
the majority of these publications reported significant weight
loss.
Twenty-four publications, including the meta-analysis,
14
reported on lipid outcomes.
14,18,23,26-35,37-42,45-49
Twenty-
three publications,
14,18,23,26-29,31-35,37-42,45-49
including the
meta-analysis,
14
reported on TG, with 13 publications,
including the meta-analysis,
14
reporting within- or between-
condition significant reductions.
14,28,29,32,33,35,37,39-41,46-48
Of
the 13 publications reporting significant reductions in
TG,
14,28,29,32,33,35,37,39-41,46-48
10, including the meta-
analysis,
14
also reported within- or between-condition
significant weight loss.
14,28,32,33,39-41,46-48
Twenty-three
publications reported on HDL,
18,23,26-35,37-42,45-49
with one
publication reporting a significant decrease in HDL in a
within-condition analysis
29
and three publications reporting
an increase in HDL in within- and between-condition
analyses.
32,35,45
Of four publications reporting significant
changes in HDL,
29,32,35,45
only one reported significant weight
loss.
32
Therefore, for lipids, out of 24 publications, with one
being a meta-analysis, fourteen reported on significant im-
provements in lipid profiles, with the majority also reporting
significant weight loss.
Twenty-three publications, including the meta-analysis,
14
reported anthropometric characteristics.
14,18,19,23,26,27,29,31,33,34,37-49
All 23 publications reported on WC,
14,18,19,23,26,27,29,31,33,34,37-49
with 16 publications, including the meta-analysis,
14
reporting within- or between-condition significant re-
ductions.
14,18,19,23,29,33,34,37,39-43,46-48
Thirteen of these
publications, including the meta-analysis,
14
also reported
within- or between-conditions significant weight
loss.
14,18,19,33,34,39-43,46-48
Six publications, including the meta-
analysis,
14
reported on WHR,
14,31,46-49
with two publications
finding significant between-condition reductions in WHR
and weight loss.
47,48
Consequently for anthropometrics, 16
out of 23 publications, one being a meta-analysis, showed
reductions in anthropometric characteristics, with the ma-
jority of these also reporting on significant weight loss.
For blood pressure, 20 publications reported on out-
comes,
14,18,23,26,27,29,30,32,34,37-40,42,43,45-49
with seven
14,18,26,29,32,39,46
and five
14,26,29,39,40
publications reporting significant
within- or between-condition decreases in systolic and dia-
stolic blood pressure, respectively. The meta-analysis was one
of the publications that reported significant reductions in
both systolic and diastolic blood pressure.
14
Seven publica-
tions, including the meta-analysis,
14
that reported significant
decreases in blood pressure also reported significant within-
or between-condition weight loss.
14,18,26,32,39,40,46
Only two publications reported renal outcomes.
45,46
Seligman and colleagues
45
found that urinary albumin
excretion rate was significantly lower in a healthy diet and
physical activity intervention compared with a control
intervention; however, weight loss was not significantly
different between the conditions. Straznicky and colleagues
46
found no between-condition difference in albumin-to-
creatinine ratio when there was a significant between-
condition weight loss.
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Additional Published Research since Systematic
Reviews for the Prevention of T2DM Project Were
Conducted
To determine whether the results of the systematic reviews
for the Prevention of T2DM Project that are published on the
EAL are consistent with literature published after 2012,
additional systematic reviews were conducted using the
previously described procedures (ie, the same methods were
used for identifying studies, with author L.M. retrieving ar-
ticles to determine methodologic quality and outcomes of
interest; determining inclusion and exclusion criteria;
extracting data; and identifying outcomes of interest). One
study was identified that evaluated the influence of MNT,
with a weight loss focus, delivered by an RDN in individuals
with prediabetes, and a significant reduction in WC was re-
ported.
50
For weight loss, 18 articles were identified,
50-67
with 12 meeting the inclusion criteria for metabolic syn-
drome
51-53,55-57,59-61,63,64,67
and six meeting inclusion criteria
for prediabetes.
50,54,58,62,65,66
These publications, except for
two that reported on the effects of intragastric balloon
treatment,
55,61
reported on nonbariatric weight loss in-
terventions. Sixteen publications reported achieving signifi-
cant weight loss reductions.
50,52-59,61-67
Eleven of the
identified studies reported significant improvements in gly-
cemic outcomes,
52-54,56-59,61,64-66
nine studies found signifi-
cant improvements in lipid outcomes,
51-53,56,57,59,61,62,64
and
nine studies reported significant improvements in anthro-
pometric outcomes.
50,52,53,55,56,58,59,61,64
Six studies reported
a significant improvement in blood pressure.
53,55-57,59,61
No
study reported renal outcomes.
DISCUSSION
Nutrition recommendations for prevention of T2DM have
been developed for the EAL, with 11 of the recommendations
established from systematic reviews. Two of the recom-
mendations, which focused on MNT and weight loss, received
the highest possible ratings for recommendations. Both sys-
tematic reviews indicated that the majority of studies in
which glycemic, WC, and/or blood pressure measures had
been taken found significant improvements in glycemic
outcomes (predominantly in FBG and 2-hour postprandial
glucose), WC, and blood pressure.
14,15,17-24,26,27,29,32-34,36,37,
39-43,46-48
The systematic review for weight loss also found
that the majority of the studies that measured TG also re-
ported significant improvements in this mea-
sure.
14,28,29,32,33,35,37,39-41,46-48
Because improvement in these
clinical parameters, especially for glycemic outcomes, is
believed to decrease risk for the development of T2DM, the
significant reductions found in the reviews should assist with
preventing T2DM.
4,10
Improvement in these clinical param-
eters (ie, glycemic outcomes, WC, TG levels, and blood pres-
sure) also increases the likelihood the criteria for diagnosis
for prediabetes or metabolic syndrome will no longer be
met.
4-6
Thus, the consistent finding from studies of higher
quality study design that MNT and weight loss improve these
clinical parameters provides strong evidence that these
nutrition approaches should be implemented to assist with
preventing the development of T2DM. The findings from the
systematic review on weight loss are also consistent with
2017 recommendations from the ADA on the prevention or
delay of T2DM.
68
The reviews also found that for both MNT and weight loss,
there was much less support that either of these nutrition
recommendations improve HDL or WHR. However, in case
these are the only clinical parameters that do not show
improvement from MNT or weight loss, as stated previously,
risk for developing T2DM should still be reduced because the
likelihood of meeting criteria for prediabetes or metabolic
syndrome has been lowered. Few studies measured renal
outcomes, albumin-to-creatinine ratio, and urinary albumin
excretion rate, so no conclusions can be drawn about the
influence of MNT or weight loss on these clinical parameters
in those with metabolic syndrome.
Although the focus of this article is to present the basis of
the systematic reviews for the MNT and weight loss recom-
mendations for the EAL Prevention of T2DM project, for this
article the reviews were updated and concisely summarized.
Findings indicate that since 2012, new investigations have
been published meeting the inclusion criteria, with these
investigations finding similar results as the initial systematic
reviews. These studies increase the quantity of investigations
demonstrating that MNT and weight loss improve clinical
parameters in individuals with prediabetes and metabolic
syndrome that should reduce the risk of developing diabetes.
It is important to note that the interventions that evaluated
the influence of MNT and weight loss on outcomes varied
tremendously in terms of use and type of dietary and physical
activity intervention, deliverer providing the intervention,
type and frequency of contact, and length of intervention.
Thus, conclusions about exactly what the MNT or weight loss
intervention should be to achieve the improvements in gly-
cemic, WC, TG, and blood pressure outcomes cannot be
drawn. The majority of the MNT dietary interventions
included in the review focused on weight loss, suggesting
that MNT may need to have a weight loss focus to be suc-
cessful for reducing the risk of developing T2DM.
16,17,19-25
Furthermore, results of the systematic review for MNT also
suggest that greater frequency of contact improves out-
comes.
18,23
To better understand how to optimize MNT out-
comes to improve the clinical parameters examined in the
systematic review, future research should examine the effect
of MNT that produces weight loss, MNT that does not pro-
duce weight loss, and frequency of contact during MNT on
clinical parameters. In addition, because few studies have
investigated how MNT influences metabolic syndrome, more
research is needed in this area. Finally, to better understand
the unique role of RDNs or international equivalents on
reducing the risk of developing T2DM, comparisons should
be made between similar interventions delivered by RDNs
and other health care providers on clinical outcomes.
For weight loss, although it was not a focus of the review,
given the current recommendations regarding adult weight
loss,
69
it is anticipated that larger amounts of weight loss
would enhance improvements in clinical parameters, further
decreasing the risk of T2DM. What is known from other
evidence-based guidelines about weight loss is that there is
no specific diet, other than reducing energy intake, that is
recommended for weight loss, a comprehensive lifestyle
intervention (eg, diet, physical activity, and behavior coun-
seling) produces greater weight loss than a diet or physical
activity intervention alone, greater frequency of contact
when delivering a comprehensive lifestyle intervention may
assist with enhancing weight loss, and bariatric surgery
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1608 JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS October 2017 Volume 117 Number 10

produces greater long-term weight loss than comprehensive
lifestyle intervention.
69
Furthermore, it is important to note
that bariatric surgery may have the potential to influence
clinical parameters using mechanisms that are not known at
this time that do not involve weight loss.
Strengths of the systematic reviews are including studies
that only have samples, or only reporting on samples, that
are at high risk for developing T2DM. In addition, only
study designs with higher quality ratings were included in
the review. The main weakness of the review was using
clinical parameters as outcomes, rather than incidence of
diabetes, and including studies with short interventions
(3 months). Limiting the studies in the reviews to only
those that measured incidence of diabetes or that were
interventions with longer time frames (ie, 12 months)
would have severely limited the number of studies
included in the reviews, reducing our ability to draw strong
conclusions.
CONCLUSIONS
Results of the systematic reviews for MNT and weight loss for
the prevention of T2DM provided strong evidence that these
nutrition recommendations will have an influence on clinical
parameters that reduce the risk of the development of T2DM.
RDNs working with high-risk populations, such as adults
with prediabetes and metabolic syndrome, are encouraged to
use these nutrition recommendations to engage in evidence-
based practice.
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AUTHOR INFORMATION
H. A. Raynor is a professor, University of Tennessee, Knoxville. P. G. Davidson is an assistant professor, West Chester University of Pennsylvania,
West Chester. H. Burns is a diabetes educator and dietitian, Endocrine and Diabetes of Southern Illinois, Herrin, IL. M. D. H. Nadelson is a clinical
assistant professor, Family Medicine Center Silver Clinic, University of Oklahoma Health Sciences Center College of Pharmacy, Oklahoma City. S.
Mesznik is an instructor, Teachers College of Columbia University, New York, NY. V. Uhley is an assistant professor, biomedical sciences, and
nutrition discipline director, Oakland University William Beaumont School of Medicine, Rochester, MI. L. Moloney is evidence-based practice
manager, Evidence Analysis Library, Academy of Nutrition and Dietetics, Chicago, IL.
Address correspondence to: Lisa Moloney, MS, RD, LD, Evidence Analysis Library, Academy of Nutrition and Dietetics, 120 S Riverside Plaza, Suite
2000, Chicago, IL 60606. E-mail: lmoloney@eatright.org
STATEMENT OF POTENTIAL CONFLICT OF INTEREST
No potential conflict of interest was reported by the authors.
FUNDING/SUPPORT
None to report.
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October 2017 Volume 117 Number 10 JOURNAL OF THE ACADEMY OF NUTRITION AND DIETETICS 1611