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IAN Research Findings: Children with ASDs Have Different Weight, Height Profile Than Typical Peers

February 17, 2009

New data from the Interactive Autism Network (IAN), a project collecting information online from families of children with ASDs all over the United States, show that children with ASDs tend to be taller than expected for their age, and heavier than expected for their height, compared to typical peers.

Please Note: These Findings Are Preliminary
The analysis presented here by the Interactive Autism Network (IAN) is preliminary. It is based on information submitted over the internet by parents of children with autism spectrum disorders (ASDs) from the United States who choose to participate. The data have not been peer reviewed -- that is, undergone evaluation by researchers expert in a particular field -- or been submitted for publication. IAN views participating families as research partners, and shares such preliminary information to thank them and to demonstrate the importance of their ongoing involvement.

We encourage autism researchers investigating these topics to apply for access to the IAN database. Contact

Parents Respond! 1,000 Children Measured Overnight
The IAN Weight and Height Questionnaire was launched on the afternoon of October 22, 2007. Families participating in IAN were notified, and got out their scales and tape measures. By the end of the next day, October 23rd, families had submitted height and weight measurements for over 1,000 children. To date, more than 2,500 Height and Weight questionnaires have been completed. Weight and height data will continue to be collected through November 21, 2007.

Why is body size an important topic to investigate?

There are at least two major reasons body size -- head circumference, weight, height, and Body Mass Index (BMI) -- are important topics to investigate in autism. First of all, differences in any of these may help point the way to specific subtypes of autism – different kinds of autism characterized by measurable physical, biochemical, or other factors. In addition, issues related to weight and BMI may be related to the future health of individuals with ASDs.

A recent paper, Clinical, Morphological, and Biochemical Correlates of Head Circumference in Autism, [i] is an excellent example of research tying a certain physical picture in ASD with other important characteristics. Studying 241 individuals with autism, ages 3 to 16, researchers found that head size tended to be large, as well as overall body size, and that those with the largest head size also tended to have more impaired adaptive behaviors, less impaired IQ, motor development, and verbal language, and a family history of allergic/immune disorders. Another study, this one focusing on 28 children with autism and 25 with PDD-NOS, discovered growth of body length was accelerated in very young children with autism spectrum disorders. [ii]

What has the IAN Project found so far?

Children with ASDs: Taller, Heavier Than Typical Peers
To compare children with ASDs and their unaffected siblings –who were considered “typical peers” for the purposes of this preliminary analysis—the IAN project used both height and Body Mass Index (BMI). (BMI is a measure that is used to calculate whether someone's weight is more or less than would be expected for their height.)

As a group, children with ASDs appear to be taller than their typical peers. Children with Asperger's Syndrome are tallest of all, while children with PDD-NOS do not appear to differ from their typical peers in height. (See Table 1.)

Table 1. Height: Children with ASDs and Unaffected Siblings

Body Mass Index

Contrary to expectations that there might be a large number of children with ASDs who are very undernourished due to gastrointestinal (GI) problems, feeding problems, or pickiness regarding foods, preliminary IAN data show no major difference in the number of children with ASDs with a BMI below the 5th percentile as compared to their typical peers.

In fact, the data show that children on the autism spectrum are more likely to be obese than their typical peers. (“Obese” is defined as having a BMI in the 95th percentile or above.) 16.2% of typical children fell into the obese category, while 23.5% of children with an ASD did so.

Some of this difference may not be due to differences in body type, but to other factors impacting children with an ASD. In fact, 41% of parents who are concerned that their child is underweight, and 35% of parents who worry that their child is overweight, report that their child has a health problem or is taking medication that contributes to the weight issue. It will therefore be important for researchers to investigate the extent to which the apparent higher rate of obesity in autism is accounted for by factors such as medication side-effects.

As shown in Table 2, below, children with Asperger's Syndrome are most likely to be obese, but those with Autism also suffer more obesity than typical peers. This is an intriguing result, with both scientific and practical implications. This data may provide support for the findings of the studies mentioned above, for example, and certainly should be taken into account by those guiding individuals with ASDs in their daily choices regarding exercise and nutrition. According to this preliminary analysis, children with ASDs may be at even higher risk for obesity than other children their age.

Table 2. BMI: Children with ASDs and Unaffected Siblings

To Share Your Thoughts About These Findings…

If you have comments and insights about these preliminary findings, please share them in the research-focused IAN Community Discussion Forum under “IAN Research Reports: Weight and Height Findings – November, 2007”. (Link: Your feedback may influence future research.

(Any member of the public may view these discussions, but to post you must join IAN Community. Go to and click “JOIN NOW.”)

What is IAN?
The primary goal of the Interactive Autism Network (IAN) is to accelerate the pace of autism research. Families affected by autism answer questionnaires over the internet, from the comfort of home. Researchers apply to IAN to use the resulting data, or to find participants for their local studies. The IAN Community ( ), meanwhile, provides evidence-based basic information on Autism Spectrum Disorders, articles by leading researchers in the field, and reports on IAN's latest findings.

To learn more about the IAN Project, please go to
To join the IAN research project, please go to

[1] Sacco, R., Militerni, R., Frolli, A., Bravaccio, C., Gritti, A., Elia, M., Curatolo, P, Manzi, B., et al. (2007). Clinical, morphological, and biochemical correlates of head circumference in autism. Biological Psychiatry, 62, 1038-1047.
[2] Van Daalen, E., Swinkels, S.H., Dietz, C., van Engeland, H., & Buitelaar, J.K. (2007). Body length and head growth in the first year of life in autism. Pediatric Neurology, 37(5), 324-330.