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Volume 19 • Issue 5 • 1000385
Research Article Open Access
Journal of Psychiatry
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ISSN: 2378-5756
Review Article Open Access
Balogun, J Psychiatry 2016, 19:5
DOI: 10.4172/2378-5756.1000385
J Psychiatry, an open access journal
ISSN: 2378-5756
Abstract
Background: It has been suggested that obesity and overweight in young people with autism spectrum
disorder (ASD) presents a challenge to conventional weight reduction measures leading to poorer health outcomes
in this population in comparison with typically developing children. In order to effectively adapt current obesity
management guidelines for use in children with ASD more needs to be understood about the prevalence of
overweight and obesity and the associated factors in this population.
Aim: The purpose of this review is to appraise the evidence on obesity and overweight prevalence in the
childhood ASD population from relevant studies selected using a computer generated database. The review
explores the link between age, gender, physical activity and obesity in childhood ASD; and highlights areas for
further research. The link between antipsychotic treatment and weight gain in childhood ASD is already well
established and this review doesn't include an appraisal of the evidence supporting this link.
Results: Compared to an obesity rate of 17% in typically developing children from the CDC’s National Health
and Nutrition Examination survey (2011-2014); eight of the eleven studies included in this review reported higher
obesity rates among children with ASD. Of these eight, three were only marginally higher than the NHANES
prevalence. The highest rate was 30% and the lowest was 10%.
Conclusion: There is a wide variation in prevalence estimates for obesity in children and adolescents with
ASD, with most studies reporting prevalence rates equal to or greater than rates found in typically developing
children. Several associated factors were identied but the strength of the evidence limits the value applicability
of these ndings. Many studies lacked a comparison group and more robust longitudinal studies are needed to
ascertain strength of association and risk.
*Corresponding author: Femi Balogun, Child and Adolescent Psychiatrist,
National and Specialist CAMHS, South London and Maudsley NHS Trust, London,
United Kingdom, Tel: 44-770786138; E-mail: femi@doctors.org.uk
Received: June 05, 2016; Accepted:September 15, 2016; Published: September
22, 2016
Citation: Balogun F (2016) Prevalence and Correlates of Obesity in Childhood
Autism Spectrum Disorders: A Literature Review. J Psychiatry 19: 385.
doi:10.4172/2378-5756.1000385
Copyright: © 2016 Balogun F. This is an open-access article distributed under
the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author and
source are credited.
Prevalence and Correlates of Obesity in Childhood Autism Spectrum
Disorders: A Literature Review
Femi Balogun*
Child and Adolescent Psychiatrist, National and Specialist CAMHS, South London and Maudsley NHS Trust, London, UK
Keywords: Autism spectrum disorder; Obesity; Overweight;
Children; Adolescents; Physical activity; Age
Introduction
Childhood obesity has more than doubled in children and
quadrupled in adolescents in the past 30 years [1]. e World Health
Organization describes the trend as one of the most serious global public
health challenges of the 21st century. In response to the crisis, the UK
government in its 2008 White paper, Healthy Weight, Healthy Lives;
a cross government strategy for England; aimed to reduce paediatric
overweight and obesity to levels prevalent in 2000 by the year 2020. A
year later, the department of health launched the Change4Life campaign
to raise awareness about diet and physical activity, and encourage
families to “eat well, move more and live longer”. Observatories such as
the National Obesity Observatory were established to track paediatric
obesity trends and monitor the eectiveness of policy initiatives.
Another reporting mechanism was the National Child Measurement
Programme (NCMP) which publishes annual UK childhood obesity
rates. Nonetheless, more action is required at a public health level to
achieve these government targets, and these include policy measures for
a sugar tax on the food industry to tackle the high caloric intake culture
of our 'obesogenic' society. With more than half of obese school age
children likely to become obese adults, the cost of obesity to the NHS is
extremely high. e Foresight report published in 2007 estimated that
direct health care costs attributable to being overweight or obese were
£4.2 billion, potentially rising to £6.3 billion in 2015 and up to £9.7
billion by 2050. A more recent analysis estimated that being overweight
or obese costs the NHS £5.1 billion per year [2].
Obese children are at greater risk of developing obesity related
diseases such as insulin resistance, type 2 diabetes, cardiovascular
and circulatory problems (heart disease and stroke), certain cancers,
osteoarthritis and some mental health disorders [3]. e morbidity and
disability burden is therefore high and obesity is a risk factor for early
death. Childhood obesity rates in the UK have levelled o somewhat in
recent years, having peaked in 2004 (ONS, 2013); however they are still
much higher than they used to be. According to data from the Health
Survey for England, in 2013, the obesity prevalence of children aged
2-15 was 15%. Rates in Wales were signicantly higher at 19% (20%
for boys). Most recent reports from the NCMP in 2014-15, put obesity
prevalence at 19.1% in children aged 10-11 and 9.1% in 4-5 year olds.
Rates in the United States are about 17% with higher rates among boys
and older children in general (NHANES, 2014).
Unfortunately, we do not have the benet of such precise obesity
prevalence data for paediatric autism spectrum disorders (ASD).
ASD is characterised by communication decits, such as responding
inappropriately in conversations, misreading nonverbal interactions, or
diculty building friendships appropriate to their age. In addition, these
young people may be overly dependent on routines, highly sensitive to
changes in their environment, or intensely focused on inappropriate
Citation: Balogun F (2016) Prevalence and Correlates of Obesity in Childhood Autism Spectrum Disorders: A Literature Review. J Psychiatry 19: 385.
doi:10.4172/2378-5756.1000385
Page 2 of 6
Volume 19 • Issue 5 • 1000385
J Psychiatry, an open access journal
ISSN: 2378-5756
items [4]. is neurodevelopmental disorder has a higher prevalence
in boys [5]. In 2008, NHS England put the prevalence of ASD among
5-16 year olds at 1%.
Why should the prevalence of obesity in children and adolescents
with ASD be any dierent from rates in their typically developing
peers? Several hypotheses abound. It has been suggested for instance,
that current guidelines for childhood obesity management and weight
control may not apply to children with ASD [6]. ese guidelines target
three core behaviours that modify weight status i.e. calorie intake,
physical activity and sedentary lifestyle. It has been postulated that
the core decits that dene ASD limit at the very least how well these
guidelines can deliver positive outcomes in children with ASD. Broadly
put, these suggestions highlight two possible theories. e rst is that
physical limitations associated with overt disability as seen in ASD and
signicant learning disability; or more subtle diculties with muscle
tone and coordination problems; hinder participation and engagement
in existing curriculum and community based exercise programs as
designed for typically developing children. e other argument is that
the core social interaction and communication decits of ASD limit
access to and participation in physical activity programs in and out of
school.
In principle, this subject has a place on the national 'Parity of
Esteem' agenda in that by meeting the physical health needs of children
with ASD; we can guarantee better outcomes for them in the area of
obesity related morbidity and mortality. is paper presents a general
review of the literature on the prevalence of obesity and overweight
in children and adolescents with ASD. It explores selected associated
factors (with a focus on age and physical activity) in an attempt to
provide answers to the question raised in the preceding paragraph. e
link between antipsychotic treatment and weight gain in childhood
ASD is well established and this review doesn't include an appraisal of
the evidence supporting this link.
Method
Computer databases (PsychInfo, Embase, CINAHL and Medline)
and Google Scholar for the period up to September 2015 were searched
for articles using key words 'autism spectrum disorder', 'pervasive
developmental disorder', 'autism', obesity', 'overweight', and' childhood'.
Inclusion and exclusion criteria were applied to the abstracts of the
papers generated from this search to obtain relevant papers included
in the review. Other relevant papers were identied by searching the
reference lists of these suitable papers.
Inclusion and exclusion criteria
Studies focused on obesity and overweight in childhood ASD or
PDD including case reports were included (Figure 1). Studies reporting
physical activity patterns levels in children and young people up to the
age of 19 with ASD were included.
Studies reporting obesity prevalence rates in other
neurodevelopmental disorders were included provided children or
adolescents with ASD were also studied. Papers focused on food
selectivity and sensitivity in children and young people with ASD
were excluded. Also excluded were studies focused on genetic factors
and chromosomal syndromes and those including young people with
physical disabilities.
All papers were in the English language (one paper may have been
translated by the authors from Chinese for inclusion in the English
literature). 12 cross sectional studies were included in the review.
Obesity was dened as BMI above the 95th percentile and overweight
was dened as MI between the 85th and 95th percentile using the
Centre for Disease Control's BMI growth reference charts.
Results
Prevalence
In a retrospective chart review involving 42 children with a diagnosis
of ASD from a tertiary clinic in Boston, Curtin et al. [7] reported a 19%
and 35.7% prevalence of obesity and overweight respectively. Compared
with data from the National Health and Nutrition Examination Study
(NHANES, 1999-2002), the investigators concluded that obesity and
overweight rates in the childhood ASD population was similar to rates
in typically developing children and the problem was as 'signicant in
children with ASD as in the general population'. e sample was small
and no sample size calculation was reported. Almost ninety percent of
the charts reviewed were of children 11 years or younger with half of
the entire sample 5 years or less. Furthermore there was no comparison
group and the sample contained no children of African-American
ethnicity. e data represented ASD children from a special population
and the reported obesity rates are unlikely to be generalizable to the
broader population of children with ASD, thus limiting the external
validity of this study.
With data from a larger sample of 2976 children collected in the
2003-2004 National Survey of Children's Health in the United States,
Curtin et al. [8], re-examined obesity prevalence in 454 ASD children
and reported higher rates of 30.4% compared to 23.6% in the non-ASD
group (p = 0.075). e data set was obtained by random digital dialling
of households across all y states of the US and DC with a response
rate of 55%. Information on height and weight was obtained by parental
report and was thus subject to information bias. Case ascertainment
was derived from a single screening question with no robust diagnostic
evidence thus increasing the risk of misclassication bias. e investigators
concluded that children with ASD were more likely to be obese than
Records screened
Title and abstract
(n=548)
Excluded
Publications with
psychophar macology f ocus
(n=82)
Excluded
Papers on genetic
syndromes, Learning
Disability a nd physical
disability
(n=12)
Excluded
ASD/PDD p ublications
without ob esity outcom es
(n=401)
Excluded
Papers on food sensiti vities
and dietar y patterns
(n=23)
Excluded
Papers on genetic
syndromes, Learning
Disability a nd physical
disability
(n=12)
Records identified through database
searching
Medline, PsychINFO, CINAHL,
Embase and Google Scholar
(n=656)
Records after duplicates removed
(n=548)
Records assessed for eligibility
meeting inclusion criteria
(n=21)
Included
Studies iden tified by
searching in refer ence lists
(n=3)
Excluded
Case reports
(n=2)
Publications included in Review
(n=19)
Studies included in Review
(n=14)
Figure 1: Attrition diagram for literature search.
Citation: Balogun F (2016) Prevalence and Correlates of Obesity in Childhood Autism Spectrum Disorders: A Literature Review. J Psychiatry 19: 385.
doi:10.4172/2378-5756.1000385
Page 3 of 6
Volume 19 • Issue 5 • 1000385
J Psychiatry, an open access journal
ISSN: 2378-5756
children without ASD; the unadjusted odds of obesity in children with
ASD was 1.42 (95% CI, 1.00, 2.02, p = 0.052) (Figure 2).
Zuckerman et al. [6] examined the prevalence and correlates of
obesity and overweight in a clinical sample of 376 Oregon children
with ASD and reported rates of 17% and 18.1% respectively. is study
like the two mentioned above, involved secondary analysis of data
not originally collected for this primary purpose; and in this case was
derived from the Autism Treatment Network Registry. Weight and
height data were obtained by trained clinical sta and ASD diagnosis
informed by ADOS records. However, the sample was drawn from
academic health centres with a mean age of 5.5 years, and problems
with generalizability to the wider ASD population are likely. Missing
data was also a weakness of the study. Using the same data registry,
Vinck-Broody et al. [9] investigated obesity and overweight in a sample
of 2769 children. e study included a comparison group of a matched
sample of children from the NHANES, 2005-2010. e prevalence of
obesity and overweight was 18.2% and 33.9% respectively and ASD was
associated with a higher risk of obesity (but not overweight relative to
the NHANES sample (odds ratio 1.16; 95% CI 1.05-1.28, p = 0.003). A
similar prevalence for obesity (17.58%) but lower rate for overweight
(15.38%) was reported by Egan et al. [10] in a study involving a
retrospective chart review of 273 children with ASD referred for
specialist treatment. e mean age of the sample was a mere 3.89 years.
By contrast, Broder-Fingert et al. [11] in their work with American
children with 'autism' and 'Asperger’s syndrome' reported an obesity
prevalence of 23.8%; a rate surpassed only by reports from Curtin et
al. [8] and Memari et al. [12] ey carried out secondary data analysis
of just under 3000 children and included a control group (obesity rate
10.9%; overweight rate 6.3%) However, no mean age was reported and
the diagnostic category 'pervasive developmental disorder not otherwise
specied' was excluded from the sample, giving rise to misclassication
bias. Overweight prevalence was reported as 13.6%. e weight status of
113 Iranian children with Autism Spectrum Disorder was investigated
by Memari et al. [12] e study sample was drawn by stratied random
sampling from relatively well functioning children aged 7-14 years
enrolled in ve autism specic schools in Tehran. All children had a
diagnosis of ASD conrmed by a child psychiatrist using DSM IV TR
criteria. No power calculation for sample size was performed and there
was no control group. e prevalence of obesity was reported at 27.4%
with 13.3% overweight. As this sample comprised children attending
'autism-specic' school in urban Iran, doubt is cast on the external
validity of these results. Nonetheless, the study does raise important
issues related to the diculty of obtaining a representative sample in
studies of this kind.
Xiong et al. [13] studied the physical status of 429 Chinese children
(the vast majority male) with autism recruited from a school for autism
that provided an Applied Behavioural Analysis course. e mean age
was 5.1 years. e diagnosis of 'autistic disorder' was conrmed either
by a paediatrician or psychiatrist based on the Chinese classication
and diagnostic criteria of Mental Disorders. Children with Asperger’s
Syndrome and 'other autism disorders' were excluded from the study
sample. Based on this sample, Xiong et al. [13] reported an obesity
prevalence of 18.4% with 33.6% overweight. However, sampling factors
and classication dierences make it dicult to compare of the children
had BMI values that exceeded the cut-o scores for obesity while 42%
were overweight. ere are several limitations to this study not least the
small sample size and the absence of a power calculation. e authors
present the highest overweight prevalence of the studies presented in
this review in an age range between just over 2 years and 12.3 years.
ere were no signicant dierences between the PDD sub-groups.
Corvey et al. [14] in their work on 1385, 6-17 year olds with ASD,
used data from the National Survey of Children's Health (2011-2012);
and reported an obesity these rates with those obtained in other studies
(Table 1).
e body mass index of y boys with pervasive developmental
disorder in the UK was investigated by Whiteley et al. [15]. Formal
diagnosis was dened as autism, Asperger's syndrome and ASD and
the boys had a mean age of 6.6 years. It is unclear how the sample was
recruited and no mention is made as to whether these were clinic or
community samples. 10% prevalence rate of 16.4% with an overweight
rate of about 10%. ey concluded that having a diagnosis of ASD
was associated with higher odds of obesity (OR 1.76, CI 1.27-2.43, p <
0.001). However, when 'secondary conditions' were controlled for i.e.
e presence of learning disability and medication use, the association
with obesity is lost. We note that 73% of their sample had a learning
disability and 25% an intellectual disability both of which were not
dened by the authors. ese comorbidity rates may not be typical
of the wider ASD population and it raises generalizability questions.
Furthermore, the accuracy of data based on parental responses to single
screening questions also places limits on the utility of these ndings.
Hill et al. [16], compared obesity and overweight rates in 5053 children
with ASD and 8844 age matched children from the general population
and concluded that obesity was higher in ASD children; however the
dierence was only statistically signicant with non-white Hispanics
aged 2-17 years and His panic children aged 2-11 year. e ASD sample
was drawn from the Autism Talks Network registry and the comparison
sample from NHANES surveys over six years to 2013. Overall they
reported an obesity prevalence of 18% among children and adolescents
with ASD and 31.8% overweight prevalence. ough constrained by
the limitations of a secondary data analysis, the study was considerably
robust on sample size and case ascertainment only including children
diagnosed by professionals using the Autism Diagnostic Observation
Schedule (ADOS).
Associated Factors
Age
In their study of 113 Iranian children, Memari et al. [12], compared
obesity rates in four age groups with one year intervals across a 7-14
year range (mean age of 9.7 years). ey found the highest prevalence
40.00
32.00
24.00
16.00
8.00
0.00
Paediat
Paediat
ric ASD
ric Obes
i
g
US and
U
K child
r
en (%)
Obesity Prevalence %
ty Prevalence in typically developi n
Obesity
Prevalence (%)
Whiteley
et
al,
2004
Curtin
et
al,
2005
Xiong
et
al, 2009*
Curtin
et
al,
2010
Memari
et
al, 2012**
Broder-Fingert
et
al,
2013
Egan
et
al,
2013
V
inck-Baroody
et
al,
2014
Zuckerman
et
al,
2014
Hill
et
al,
2015
Corvey
et
al,
2015
NHANES,
1999-2000
NHANES,
2009-2010
UK
Prevalence ONS
2013
NHANES
2011-2014
Prevalence Studies (* Chinese Study, **Iranian Study)
Figure 2: Paediatric obesity rates in autism spectrum disorder.
Citation: Balogun F (2016) Prevalence and Correlates of Obesity in Childhood Autism Spectrum Disorders: A Literature Review. J Psychiatry 19: 385.
doi:10.4172/2378-5756.1000385
Page 4 of 6
Volume 19 • Issue 5 • 1000385
J Psychiatry, an open access journal
ISSN: 2378-5756
Authors Country Obesity Prevalence
rate (%)
Overweight
prevalence rate (%)
Sample size
(N)
Sample Mean age in years (where mean age
is not provided age range is given in italics)
Whiteley et al. [15] UK 10 42 50 6.6
Curtin et al. [7] USA 19 36 42 2-18
Xiong et al. [13] China 18.4 34 429 5.5
Curtin et al. [8] USA 30.4 483 3-17
Memari et al. [12] Iran 27.4 13 113 7-14
Egan et al. [10] USA 17.58 15 273 3.89
Vinck-Baroody et al. [9] USA 18.2 34 2769 6.45
Zuckerman et al. [6] USA 17 18 376 5.5
Broder-Fingert et al. [11] USA 23.83 14 2976 2-20
Hill et al. [16] USA 18 33.6 5053 2-17
Corvey et al. [20] USA 16.4 9.9 1385 6-17
Table 1: Summary table of studies investigating obesity prevalence in paediatric ASD populations.
in the 13-14 year group (p = 0.06) with girls more likely to be obese
than boys. Half the sample was within normal BMI limits, thus limiting
the sample size of obese children. Furthermore, younger children were
not included in the study, thus limiting comparison across the entire
paediatric age range. eir conclusion that obesity is more prevalent in
older children with ASD is consistent with reports by Broder-Fingert
et al. [11].
Egan et al. [10] reported relatively high obesity prevalence rates
(17.58%) in a study of US preschool children with ASD (range 2.5 to
5 years; mean age 3.89, SD = 0.91). ey suggest these ndings are
consistent with prior research trends that demonstrate lower obesity
rates in younger typically developing children. However, the ndings do
question whether age is indeed a risk factor for obesity in the paediatric
ASD population. e reported obesity rates are higher than those seen
in typically developing children of the same age; and suggest that weight
management interventions may need to commence much earlier than
previously realized. Unfortunately, no comparisons with older children
were made. Zuckerman et al. [6] in their study of 376 young children
with ASD (mean age of 5.5 years, SD 3.2) reported similar obesity
rates but did not nd any correlation between age and weight status.
In China, Xiong et al. [13] also studied the weight status of younger
children with a mean age of 5.1 years (SD=1.7; range 2-11) with 71% of
the sample aged 5 or younger. Obesity rates were signicantly higher in
the 6-11 year group (21.8%) than in the 5 and under (17%). e data
was not compared to rates in age-matched typically developing Chinese
children. In a investigation of 50 UK children diagnosed with pervasive
developmental disorders, and aged between 2.4 to 12.3 years, Whiteley
et al, 2004 reported a relatively low obesity rate of 10%. e mean age of
the sample was 6.6 years and there was no control group.
Vinck-Baroody et al. [9] studied the weight status of children with
ASD in a large North American multisite clinic sample. e inclusion
criteria included age 2-17 years, though more than half the sample
was 5 years or younger and only 9% were adolescents age 12-17. e
investigators admit that as a whole the data bank from which the sample
was drawn is young. Rates of obesity were compared with typically
developing children in the national population sample (NHANES) and
the unadjusted OR in the 12-17 year group was 1.59 (95% CI,1.22-2.06;
p < 0.05). e OR in the 2-5 and 6-11 year groups showed no signicant
association with obesity further suggesting that the risk of obesity in
children with ASD may increase with age. A similar trend was reported
in the Curtin et al. [7] study. Over 80% of the 42 children with ASD
investigated were 11 years or younger with half the sample aged 2-5
years and only 12% aged 12-19 years. Obesity rates were highest in
the 12-19 age groups (50%) and lowest in the 2-5 age groups (14.2%).
e numbers in each age group however were quite small limiting the
power of the study and the external validity of these ndings. Broder-
Fingert et al. [11] also demonstrated higher obesity rates among older
age groups in their study of almost 3000 children with ASD. Compared
to children aged 6-11years, the odds of obesity were higher in children
aged 12 to 15 years (OR 1.87 CI: 1.33-2.63). e older children (age 16
and above) had even higher odds (OR 1.94 CI: 1.39-2.71).
Physical activity
It has been suggested that access to physical activity sessions as part
of a healthy lifestyle or indeed a weight management intervention by
children with ASD may be signicantly restricted due to factors uniquely
related to ASD [6]. ese factors broadly fall into two categories i.e.
those related to physical limitations such as impaired coordination
and those related to impaired social communication which throws up
barriers to participation in group exercises; during school recess and at
other times. Atypical physical activity among children and adolescents
with ASD has been suggested as an explanation for high obesity rates
in this population. Pan and Frey [17] examined the physical activity
patterns of youth with autism spectrum disorders using accelerometry
and data obtained by questionnaire; and found that older children
with ASD exercise less than their younger counterparts. Elementary
school youth were more active than their middle and high school peers
irrespective of day of the week or time of day. ey also didn't nd any
consistent patterns in physical activity in youth with ASD. However,
the quality of the data is limited by a small sample size (n=30), with
no sample size power calculations; a predominantly male cohort, no
comparison group of typically developing children and a selection of
high functioning children. ese all raise questions about the external
validity of their results.
Sandt and Frey [18] went further by comparing physical activity
levels between children with and without ASD. ey found that there
was no signicant dierence between the two groups and based on
their data concluded that school activities and unstructured aerschool
activities provide sucient opportunities for children with ASD
to be active. eir results are informative and attempt to answer the
important question of access to physical activity programs by children
with ASD. However, these ndings are also unlikely to be authoritative
or generalizable. A small convenience sample of volunteers was used
(n=15) and all the children were younger than 12 years. More work in
this area was done by Tyler et al. [19] who assessed physical tness and
physical activity in a group of young people with ASD and compared
them to children without a diagnosis of ASD (typically developing
peers). Although the sample sizes were small (n=17 in the ASD group,
n=12 in the non-ASD group) and selection was not randomized; case
ascertainment was relatively robust. e autism diagnostic observation
Citation: Balogun F (2016) Prevalence and Correlates of Obesity in Childhood Autism Spectrum Disorders: A Literature Review. J Psychiatry 19: 385.
doi:10.4172/2378-5756.1000385
Page 5 of 6
Volume 19 • Issue 5 • 1000385
J Psychiatry, an open access journal
ISSN: 2378-5756
schedule (ADOS) was administered to conrm the diagnosis in
each participant of the case group. e two groups were signicantly
dissimilar in age (the ASD group was made up of mostly 15 year olds
and the control group were mostly 9 year olds). ey concluded that
children with ASD spent less time in light, moderate and moderate-
vigorous physical activity and more time in sedentary behaviour
compared to their typically developing peers. In spite of these slight
dierences the authors explain that aspects of physical tness are
attainable and comparable to peers without ASD.
ese ndings are broadly consistent with existing evidence
in this eld and further stress the point that children with ASD can
successfully participate in existing physical activity programmes. In a
bid to address the generalizability and small sample size limitations of
previous studies, Corvey et al. [20] studied the links between an ASD
diagnosis and four outcomes viz. obesity, overweight, physical activity
and sedentary behaviours in a large sample (n=1385) of American
children. e data was drawn from pre collected information in the
CDC's National Survey of Children's Health 2011-2012 which relied
solely on parental reports during a telephone survey. Parental responses
were dichotomized based on answers to two screening questions
related to physical activity and screen time which only explored activity
in the preceding week. In addition if a child had undertaken MVPA
(moderate to vigourous physical activity) for 20 minutes or more in
six but not seven days in the last week, the response was dichotomized
to zero. ey found no signicant association between ASD and a lack
of physical activity (though children who also had a learning disability
were found to have signicantly lower odds of engaging in physical
activity at recommended levels. ey also didn't nd any signicant
association between ASD and sedentary behaviour (2 or more hours
of screen time/day); however, the presence of intellectual disability
(which was ill dened by the authors) was associated with higher
odds. ere are limitations to the data as outlined in the prevalence
paragraph above but it is also important to note that the sample in this
study had a 73% comorbidity rate for learning disability and about a
quarter has 'intellectual disability'. Nonetheless, these results reect
reports from previous studies. In contrast, Pan et al. [21], demonstrated
that students with ASD were less physically active overall than their
typically developing peers. ey studied the daily physical activity and
proportion of time spent in MVPA in small convenience sample of 30
Taiwanese students aged 12-17 years with a diagnosis of ASD using
uniaxial accelerometry. e comparison group was age matched with
no diagnosis of ASD and there was no signicant dierence in weight
and BMI between the groups. ey found a signicant dierence in the
proportion of time spent in MVPSA activity and the percentage in each
group that were compliant with physical activity guidelines. e small
sample size and convenient sampling may make these ndings dicult
to replicate and indeed generalise.
Discussion
Compared to an obesity rate of 17% in typically developing children
from the CDC’s National Health and Nutrition Examination survey
(2011-2014); six of the nine studies included in this review reported
higher obesity rates among children with ASD. Of these six, three were
only marginally higher than the NHANES prevalence. e highest rate
of 30% was reported by Curtin et al. [8] Memari et al. [12] and Broder-
Fingert et al. [11] reported rates of 27.4% and 23.8% respectively. ere
are problems with the data as outlined above and one must question
the validity of these ndings. Most of these prevalence studies didn’t
report suciently robust case ascertainment procedures and there are
inconsistencies with what was included as ASD and what was not.
Establishing if obesity rates are inherently higher in ASD children
is an essential rst step in understanding whatever mechanisms
underlies this phenomenon. Unfortunately, the current evidence still
remains largely inconclusive. e studies reviewed in this article are
both inconsistent in their ndings and dierent in their methodology;
making meaningful comparisons across studies dicult.
e diagnostic criteria varied across studies and given that the
larger studies were based on secondary data analysis, utilizing data not
originally collected for the purpose of answering the research question
on obesity rates, problems with missing data and measurement bias
were evident. On the other hand the two studies reporting rates lower
than the NHANES rate, Curtin et al. [7] and Whiteley et al. [15] were
based on very small samples with no sample size power calculations.
e research base in this area is undoubtedly sparse and more robust
studies are required, preferably of a prospective nature to clarify these
ndings. Previous reviews have at the very least suggested that the rates
of obesity in children with ASD are at least as high as those found in
their neurotypical peers. Based on the data presented here we must now
consider that obesity rates in ASD children are indeed higher than in
typically developing children; and these children are at greater risk of
the mental and physical health consequences of obesity.
Possible explanations for these higher obesity rates in ASD
include 'food faddiness' (being exceptionally fussy about food) and
sensory diculties related to diet; increased calorie intake, sedentary
lifestyle (characterised by preoccupation with arm chair entertainment
technology i.e. games consoles, long hours watching television) and
lack of physical activity. It is essential to know if children with ASD can
take up physical activity programs as prescribed for typically developing
children and this has been the central theme of the very few studies
devoted to physical activity levels and patterns in ASD children. is
review included three studies. e physical activity recommendations
for children are an hour a day of moderate to vigorous activity (MVPA)
on all or most days and for adolescents, at least 20 minutes of MVPA
three or more times a week. e data suggests that most children
with ASD were capable of achieving these recommendations and no
signicant dierences in activity levels and patterns were found in ASD
children compared with children without ASD [18].
ere are reports that access to existing physical activities in school
or outside of school hours may be restricted for ASD children due to
social communication diculties. However, a descriptive report of a
small group of children with ASD by Schultheis et al. [22] based on
the TEACHH program demonstrates that with minor and inexpensive
modications, physical activity sessions can be successful in ASD
children and based on the evidence should be incorporated into
weight management programs targeted at ASD children. As would
be expected in the general population, age and gender showed the
strongest association with obesity in these review i.e. higher rates in
girls and older children. is reects a decrease in physical activity
from childhood into adolescent is reported. e association between
obesity and psychotropic medication i.e. atypical antipsychotics was
either not explored in the review papers or the number of children on
these medications was small. Memari et al. [12] for instance reported
only a weak positive correlation between antipsychotic treatment and
obesity; and that was only in boys (only 23 of 113 study participants were
girls). Antipsychotic medication is widely used in the management of
behavioural diculties in children with ASD and the obvious question
is 'are the apparent higher obesity prevalence rates in ASD children
independent of the contribution from antipsychotic use?' Findings from
this review suggest that antipsychotic medication further increases the
risk of obesity in ASD children over and above an existing risk. Corvey
Citation: Balogun F (2016) Prevalence and Correlates of Obesity in Childhood Autism Spectrum Disorders: A Literature Review. J Psychiatry 19: 385.
doi:10.4172/2378-5756.1000385
Page 6 of 6
Volume 19 • Issue 5 • 1000385
J Psychiatry, an open access journal
ISSN: 2378-5756
et al. [20] reported that the signicant association found between ASD
and obesity in their study disappeared when medication and ‘possible’
secondary conditions were accounted for. But several studies in this
review reported higher obesity rates in ASD children were not on
antipsychotic medication.
Conclusion
e available evidence on the prevalence of obesity in paediatric
ASD is largely inconsistent; though recent studies appear to coalesce
around a similar prevalence. However, patterns and trends emerging
from the data, (more so recent studies) appear to support the assertion
that the odds of obesity may be slightly higher in children with ASD
compared to their typically developing peers. Single studies from non-
Western populations such as Iran and China also seem to support this
conclusion. Obesity prevalence is also directly related to age with higher
odds in older children. ASD is a pleomorphic disorder with signicant
comorbidity, making research in this area dicult. Several factors are
likely to contribute to the risk of weight gain in ASD children and more
robust research is required to elucidate these. e review ndings also
have some clinical utility, the risk of obesity increases with the advent
of adolescence and a corresponding decline in physical activities. is
transition requires targeted weight management interventions in this
population.
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Citation: Balogun F (2016) Prevalence and Correlates of Obesity in Childhood
Autism Spectrum Disorders: A Literature Review. J Psychiatry 19: 385.
doi:10.4172/2378-5756.1000385
