Title of article:

Relating body mass index to figural stimuli: population-based normative data for Caucasians

Authors: Bulik CM,Wade TD, Heath AC, Martin NG, Stunkard AJ, Eaves LJ.
Journal: Int J Obes Relat Metab Disord, Oct 2001;25(10):1517-24

Abstract

OBJECTIVE: To establish body mass index (BMI) norms for standard figural stimuli using a large Caucasian population-based sample. In addition, we sought to determine the effectiveness of the figural stimuli to identify individuals as obese or thin. DESIGN: All Caucasian twins born in Virginia between 1915 and 1971 were identified by public birth record. In addition, 3347 individual twins responded to a letter published in the newsletter of the American Association of Retired Persons (AARP). All adult twins (aged 18 and over) from both of these sources and their family members were mailed a 16 page 'Health and Lifestyle' questionnaire. SUBJECTS: BMI and silhouette data were available on 16 728 females and 11 366 males ranging in age from 18-100. MEASUREMENTS: Self-report information on height-weight, current body size, desired body size and a discrepancy score using standard figural stimuli. RESULTS: Gender- and age-specific norms are presented linking BMI to each of the figural stimuli. Additional norms for desired body size and discrepancy scores are also presented. Receiver operating curves (ROC) indicate that the figural stimuli are effective in classifying individuals as obese or thin. CONCLUSIONS: With the establishment of these norms, the silhouettes used in standard body image assessment can now be linked to BMI. Differences were observed between women and men in terms of desired body size and discrepancy scores, with women preferring smaller sizes. The figural stimuli are a robust technique for classifying individuals as obese or thin.

Comments and Key points

This interesting article proved that these "figures" in the picture below1, are actually useful. People can describe themselves accurately by choosing a picture. Go ahead, try it yourself.

figures of body shapes

Men's average BMI for each figure-number was shown in this table

Men: 1 2 3 4 5 6 7 8 9
BMI: 19.8 21.1 22.2 23.6 25.8 28.1 31.5 35.2 41.5

Women's average BMI for each figure-number was:

Women: 1 2 3 4 5 6 7 8 9
BMI: 18.3 19.3 20.9 23.1 26.2 29.9 34.3 38.6 45.4

Did you try it? Does your actual BMI seem close to the averages from these tables?

Well, maybe not. It turns out that BMI changes with age, even if your body shape (figure-number) stays the same during your life. More on this below.

 

This article also showed that when obesity is defined as BMI of 30 or more, the graphs below showed that obese women had figure=6, and obese Men had figure=7 (or higher).

The article also did additional analyses and claims that figure=6 is the best overall definition of "obesity" for both men and women. However, their article lacked sufficient detail to prove this claim, and although it may be reasonable for women, my personal opinion, based on the graphs shown above, is that figure 7 is a more suitable definition of obesity for men.

 

Now, here an the interesting part: BMI changes with age. Consider slim women and men, with figure numbers 3 and 4. As the graph below shows, Men and Women who described their body figures as type 3 or 4, also had higher BMI values in middle ages, compared to younger or older adults. Said another way, it seems that, even if body shape stays stable with age, BMI will change with age.

Slim BMI changes with Age

I was looking for evidence like this, and I think it is an important demonstration of what the appropriate curve-shape should be, of body mass index changing with age.

References

  1. Standard figural stimuli. by Dr. A. Stunkard. From Stunkard A, Sorensen T, Schulsinger F. Use of the Danish Adoption Register for the study of obesity and thinness. In: Key S, Roland I, Sigman R, Matthysse S (eds). The genetics of neurological and psychiatric disorders. Raven Press: New York; 1983.

Review & comments by Steven B. Halls, MD, Last modified 23-June, 2008. Copyright
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