Body mass index, or BMI, a figure derived from a comparison of your height to your weight, can be used to assess the extent of overweight and obese persons in a population. Your doctor or fitness trainer may also use it as a useful measure of whether your weight falls in the healthy range of 19 to 24. At the low end of the scale, BMI can be used to indicate anorexia nervosa, an emotional disorder based on fear of gaining weight.
Size
Peter Beumont at the Department of Psychiatry and colleagues at the University of Sydney and colleagues undertook a review of data in medical literature to determine if a standard measure of under-nutrition could be found. They noted in an article published in the "International Journal of Eating Disorders" that a BMI value of 16 or less provides a useful criterion and used this cutoff to successfully measure a group of 150 anorexia nervosa patients. For a typical adult woman standing 5 feet 4, a BMI of 16 equals 93 lbs.
Considerations
The Diagnostic and Statistical Manual of Mental Disorders or DSM considers a body weight below 85 percent of the norm to indicate anorexia nervosa. This correlates to a BMI of around 17.5, according to Marcia Herrin, author of "Nutrition Counseling in the Treatment of Eating Disorders." For a typical adult woman standing 5 feet 4, a BMI of 17.5 equals 102 lbs.
Time Frame
This BMI cutoff of 17.5 cannot be applied to female patients under age 20 or to male patients, Herrin notes. Some academics recommend that health care providers look instead at the fifth percentile of BMI as the criteria for weight loss to screen children and adolescents and at a BMI of 19 or lower as indicating anorexia in males.
Warning
BMI may not effectively screen all anorexic adolescents. "Strategy Development Workshop For Public Education On Weight And Obesity" notes an example of an 18-year-old female, 5 feet 4 ½ inches tall, who weighed 120 lbs. and had a BMI of 20.1, who had multiple signs and symptoms indicating semi-starvation, including a depletion of total body potassium.
Significance
Israeli fashion photographer Adi Barkan learned that 40 percent of Israeli models had anorexia. He convinced Israel's Knesset in 2005 to introduce a bill requiring models to have a BMI of at least 19 and to pass a health exam.
Expert Insight
Very low-weight anorexics, with a BMI below 15, may engage in restless physical movements including pacing, rocking, toe taping or standing instead of sitting, Herrin writes. Fidgety behavior may be uncontrollable biological reactions to starvation and indicate the need for supervised care.
References
- PubMed.gov: Use of percentiles for the body mass index in anorexia nervosa: diagnostic, epidemiological, and therapeutic considerations
- "Nutrition counseling in the treatment of eating disorders"; Marcia Herrin; 2003
- ELLEgirl: Body image survey
- Guardian.co.uk: Shaping a nation
- "Strategy Development Workshop for Public Education On Weight And Obesity;" 2004
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