Subscribe to Obesity Panacea
Subscribe to Obesity Panacea
Subscribe to Obesity Panacea by mail
 Photo by Dave_mcmt

A very interesting article came out this past week in the journal Obesity.  Dr H Shelton Brown III and colleagues at the University of Texas School of Public Health examined how a child's assessment of their own body size (e.g. lean, overweight, or obese) is influenced by the body size of their classmates.  Subjects consisted of male and female students in grades 4, 8 and 11.  All students had their height and body weight measured, which were used to calculate their body mass index (BMI).  This objective measure of obesity was then compared to the students' response on a questionnaire, which asked:

“Compared to other students in your grade who are as tall as you, do you think you weigh “The right amount,” “Too much” or “Too little(or not enough)”?

They found that for children in grades 4 and 8 (but not those in grade 11), a higher average BMI in their classmates was associated with a significant under-estimation of their own body weight.  In other words, if an obese student was surrounded by overweight and obese classmates, they were more likely to estimate that they weighed the "right amount", rather than "too much". 

It is interesting, and not terribly surprsing, that students assess themselves based on their peer group, rather than a scientific abstraction like BMI.  I'm a distance runner, and many times I have heard people say that after being around other runners for several years, they start to think of a runner's body as the norm, even though it obviously is not (it's not surprising that disordered eating is quite high among distance runners).

This study is especially interesting in light of past research showing that obesity and other health behaviors like smoking tend to spread through social networks, which I blogged about here in one of my first posts last November.  Could it be that individuals are less likely to address their own obesity if it is the norm for their peer group?  Some have even suggested that targeting social networks, rather than individuals, may be the most effective way to prevent and treat obesity at the societal level.  In fact, Dr Brown and colleagues suggest that interventions that focus on the school, rather than the individual, may be the best way to promote healthy body weights in children, and I think that it is a very reasonable suggestion (even though the Comments section on many of our posts suggest that many still feel obesity is about "personal choice", and nothing more).

This study adds to the growing body of evidence that obesity, as well as our perception of obesity, are influenced by those around us.  If we want to see healthy behaviors in our society (and in our youth) as a whole, targeting individuals one at a time is probably not the most effective way to go about it.  Interventions that target the school (or even better, the community) are the only way we are going to gain any ground against the current childhood obesity epidemic.


Related Posts:

1.  Food addiction - fact or fiction?
2.  Eating with friends - a cause of weight gain?
3.  Want to avoid weight gain? Stay single!

Brown, H., Evans, A., Mirchandani, G., Kelder, S., & Hoelscher, D. (2009). Observable Weight Distributions and Children's Individual Weight Assessment Obesity DOI: 10.1038/oby.2009.168

Enjoyed this story? Share it with your friends by clicking the buttons below!

Twitter Facebook Digg It! Stumble Delicious Technorati

To get future posts delivered directly to your email inbox or to your RSS reader, be sure to subscribe to Obesity Panacea.
You can leave a response, or trackback from your own site.

6 Response to "Self-assessment of obesity in children is influenced by body weight of their classmates"

  1. Richard Eis Said,

    Extrapolating out, could that mean that a society has a tipping point after which there is an increase in the change of weight of the population in general because the bigger size becomes the norm?

    ie the population in general gets bigger more quickly, after the tipping point.

    Posted on June 29, 2009 at 2:22 PM

  2. Travis Saunders, MSc Said,

    @ Rihcard,

    That is certainly one of the implications that I would take from it. Although on the more positive side of things, it might mean that we only need to get a certain critical mass of people in a social network to adopt healthier behaviors, and that the rest will follow suit.

    Posted on June 29, 2009 at 2:28 PM

  3. Kate Porter Said,

    Is that the actual question students were asked?

    Maybe I'm too literal, but that question to me seems to be asking students not to estimate their body weight relative to "normal" but instead to estimate it relative to the average body weight of their classmates.

    I.e., it seems to me that the question is asking students "do you think you weigh more than, the same as, or less than your classmates", not "do you think your body weight is normal" or "what is your BMI"--which is what this post seems to imply is being asked.

    It's the phrasing of the question that's problematic. If you ask students to compare themselves to their classmates, they're going to tell you whether they think they're bigger, smaller, or the same size. But that doesn't necessarily tell you whether they recognize that the average weight of their classmates is too high, too low, or "just right".

    If this is the actual question that's asked, then it's possible for an overweight student surrounded by overweight students to both a) recognize that s/he (and other students) is overweight AND b) answer "just right".

    Posted on July 2, 2009 at 2:10 PM

  4. Travis Saunders, MSc Said,

    @ Kate,

    You make a good point and yes, that is the exact wording they used. It would be ideal if the authors had just said "Do you think you weigh the right amount, too much, or too little?". As it is, it's possible that it did pre-condition the students a bit. From the methods, it sounds like this was a post-hoc analysis, which may explain why the wording wasn't ideal.

    But that being said, the meat of the question was still "do you weight the right amount, too much, or too little", not "do you weigh more, less, or the same as most of your classmates". If a child were to recognize that they and their classmates were overweight, I don't think they would answer that they weigh "the right amount". If they recognized that they were all overweight, they would still probably pick "too much".

    I'll concede that the scenario you describe is plausible, but I don't think it's likely to completely explain their results.

    Posted on July 2, 2009 at 5:43 PM

  5. RJ Said,

    We hear a lot about BMIs - and in your article you referred to the body mass index (BMI) as an " objective measure of obesity"

    The BMI isn't actually a measure of obesity on an individual level.

    World class athletes who are very muscular will be obese by this measure (when they in fact have very low body fat, and are super-fit)

    It also varies depending on race/ethnicity - for example Pacific Islanders/Maori tend to have heavier bones, more muscle per pound, and the obesity threshold moves, depending on the race of the person.

    My understanding is that BMIs were developed to measure the levels averaged across a population - changes in a populations average BMI would be useful information.

    I am concerned that too often, in diet/health/beauty magazines in particular BMI is used to stigmatise healthy people of a certain heritage (when sometimes people with an acceptable BMI can be quite unhealthy).

    As I understand it, the better measure is waist circumference.

    I like your blog, and appreciate the analysis and approach - please take this comment as a comment not a complaint - and a reminder that we need to be careful how we use the BMI measurement.

    Posted on July 23, 2009 at 6:40 AM

  6. Travis Saunders, MSc Said,

    @ RJ

    I agree with you 100%. Peter and I are big proponents of using WC as opposed to, or in conjunction with BMI. In this post, I was referring to BMI as "objective" as opposed to "subjective" measures such as self-report questionnaires. Your point is well taken.


    Posted on July 23, 2009 at 7:44 AM


Blog Archive

Recent Posts

Peter's Travel Adventures on PhD Nomads

About Us

We are PhD students in the School of Kinesiology and Health Studies at Queen's University in Kingston, Ontario. Our research focuses on the relationships between obesity, physical activity, and health risk. This blog is our attempt to consider the many "cures" for obesity that we read about on a daily basis. Enjoy.


The opinions expressed here belong only to Peter and Travis and do not reflect the views of any organization. Any medical discussion on this page is intended to be of a general nature only. This page is not designed to give specific medical advice. If you have a medical problem you should consult your own physician for advice specific to your own situation.

Donate To Obesity Panacea