Is thinner always healthier?

Although most Americans assume that thinner bodies are always healthier, recent studies have questioned that assumption.

  • In 2006, the American Journal of Clinical Nutrition published a study in which “men with a Body Mass Index (BMI) below 23 and women with BMI below 22.3 were actually at highest risk of death” (“BMI Faulted” 2006). 
  • In the same study, physicians noted that a low BMI can be particularly problematic for the elderly, because it is often associated with poor nutrition and reduced muscle mass.
  • A 2005 study published in the Journal of the American Medical Association (JAMA) reported that people who are moderately overweight (though not obese) face a lower risk of death than people whose weight is defined as "normal" according to government guidelines (“Fat Chance” 2005). 
  • The same study reported that those with a BMI of less than 18.5 (considered "underweight") have the same risk of death as the obese. 

BMI:  Body Mass Index

The Body Mass Index (BMI) is a figure based on one's height and weight. BMI generally correlates with a person's level of body fat, so using BMI is a quick and inexpensive way to assess body fat and spot potential health problems. However, recently researchers have begun to question its usefulness as a measure of overall health.

How accurate is the Body Mass Index?

  • BMI is not able to distinguish between body fat and muscle mass, causing some individuals to be termed “overweight” when it is their muscle mass which makes them heavier.
  • BMI does not account for body differences that may be linked to sex, age or race.
  • The use of BMI for assessing children can be particularly problematic. Researchers at the USDA Children’s Nutrition Research Center found that 1 in 6 children in their study had an unhealthy level of body fat even though their BMI was in the “normal” range.  And, of the children considered obese based on their BMI, 1 in 4 of them actually had a normal level of body fat.
  • BMI also does not reveal the location of body fat.  This is important since recent research indicates that abdominal fat in particular is associated with a whole range of serious health problems.

Cultural variation in body mass

Research both within the United States and around the world has demonstrated that different cultural and racial groups have different body average body types. Different populations have a genetic predisposition toward larger bodies, smaller bodies, more muscular bodies, or bodies with a higher percentage of body fat.

  • Research has found that Asian populations have higher average body fat, and are at greater risk for cardiovascular disease and Type 2 diabetes at a lower level of BMI than those of European or non-Hispanic White descent.
  • A 2004 study found that within the United States BMI varies by racial/ ethnic group, as does the association between BMI and body satisfaction.
  • White males had a higher than average BMI, but the highest degree of body satisfaction of all the male groups.
  • Women of Chinese descent had the lowest BMI and the highest level of body satisfaction of all the female groups.
  • African American women had the highest BMI of all the female groups, but expressed a high degree of body satisfaction.

Ask yourself

How much importance should we place on BMI when assessing overall health?

Does your cultural heritage affect the way you perceive your own body?

References

  • BMI Faulted as Obesity Gauge (2006, November) Tufts University Health and Nutrition Letter, Vol. 24, no. 7, pp. 1, 3.
  • BMI poor indicator of body fat in individual kids. (2000, June) Journal of the American Dietetic Association, Vol. 100, no. 6, pp. 628.
  • Deurenberg, P., Deurenberg-Yap, M., Foo, L.F., Schmidt G., & Wang, J. (2003) Differences in body composition between Singapore Chinese, Beijing Chinese, and Dutch children. European Journal of Clinical Nutrition, Vol. 57, pp. 405-409.
  • Evans, E. M., Rowe, D. A., Racette, S. B., & McAuley, E. (2006) Is the current BMI obesity classification appropriate for black and white postmenopausal women?International Journal of Obesity, Vol. 30, pp. 837-843.
  • Fat Chance? (2005, July) Tufts University Health & Nutrition Letter, Vol. 23, no. 5, pp. 1-2.
  • Wang, L. H., Chen, Y. C., Chung, A. K., Poon, G., Polong, L, & Tam, C. F. (2007, September) Age, gender and ethnic differences in prevalence of overweight and obesity in Asian American college student and their parents using different BMI cutoffs. College Student Journal, Vol. 41, no. 3, pp. 583-600. 
  • Yates, A., Edman, J., & Aruguete, M. (2004) Ethnic Differences in BMI and Body/Self-Dissatisfaction Among Whites, Asian Subgroups, Pacific Islanders, and African-Americans. Journal of Adolescent Health, Vol. 34, pp. 300-307.