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Miscellaneous
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The body mass index (BMI) and being overweight
Originally Published: July 09, 1999
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Dear Alice, Could you clarify the Body Mass Index deal? According to the chart at www.nutritionnewsfocus.com, I am "slightly overweight" because I am 5' 5-1/2" tall, and weigh 160 lb. I am also very muscular and have a large frame. The lower BMI readings are labeled "ideal," but I've heard muscle weighs more than fat, so if the chart does not include the muscle factor, is it basically saying that it's "ideal" NOT to have extra muscle? I look slender and have never been told by a doctor to lose weight. I'm a twenty-four-year-old female, lacto-ovo-vegetarian, and get lots of exercise, including walking and frequent "sweaty" Nordic Track workouts. --Scales
Dear Scales, A tremendous amount of press has been given to the Body Mass Index (BMI) charts and the "strict" standards many people feel the U.S. government has imposed upon the population. The truth is, most of these articles and news reports don't tell the entire story. Alice is glad you asked this question and would like to set the record straight. Body Mass Index is a ratio of weight to height. It is calculated as follows:
The big hoo-ha occurred in June of 1998 when the National Heart, Lung, and Blood Institute published its Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. In The Evidence Report, the definitions are:
The rationale behind these numbers is that, across large population groups, there is an increased prevalence of certain diseases in people with a BMI over 25, and a much greater risk of disease and death in those with a BMI over 30. Being overweight or obese substantially raises the risk of developing:
For health reasons, new guidelines regarding healthy weight ranges were established. A panel, including doctors, researchers, and professors from renowned universities, hospitals, and government agencies, systematically reviewed published scientific literature that met specific criteria. They developed recommendations based on their analysis of this information. It's important to realize that many details were taken into account in putting together this report. The intention of the panel was to provide targeted information to doctors and other health care professionals on how to detect, treat, and prevent disease -- particularly those caused or worsened by being overweight or obese. It provides a rationale for weight control as it relates to disease prevention. These guidelines are for adults -- they do not apply to children or adolescents. Overweight and obesity result from a complex mix of factors, including genetics and environment. Taking in too many calories, being inactive, or a combination of both could be contributing factors. An important point here is the relationship between being overweight or, better yet, overfat, and disease development. BMI often doesn't tell the entire story. For example, consider your waist-to-hip measurement ratio (hips can be measured from the outside of one hip to the outside of the other): it should be equal to or less than 1.0 for men and 0.8 for women. Increased risk is associated with excess abdominal fat -- the apple body shape (vs. pear). Other risk factors for developing disease are important to assess. A health care provider must use his/her clinical judgment to determine whether or not a person really does need to lose weight. Also make sure your provider talks with you about your family history, personal health and weight history, depression, stress, exercise habits, and any other medical, physical, and psychological conditions that could affect your health. Many web sites, books, and articles that publish BMI charts tend to simplify the message. A trained athlete or physically fit individual is NOT the target of this message. These BMI charts are a tool to be used as one part of an overall health assessment. Over large population groups, many people with BMIs in the upper range, and high waist measurements or waist-to-hip ratios, are the folks with whom doctors need to discuss various aspects of health. A fit, well-nourished person with developed muscles may have a higher BMI, but it's due to increased muscle mass. Hopefully, this answer has clarified some of the misunderstanding about BMI. Focus on your overall health, fitness level, dietary variety, and self-satisfaction. Your well-being is certainly much more than just an absolute number.
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