Waist Circumference Classifications

Waist Circumference Classifications



Increased $32 in. (80 cm) $37 in. (94 cm)

Substantially increased $35 in. (88 cm) $40 in. (102 cm)

Waist Circumference and Waist-to-Hip Ratio. Report of a WHO Expert Consultation. Geneva: WHO body mass index (BMI) A measure of relative body weight correlating highly with more direct measures of body fat, calculated by dividing total body weight (in kilograms) by the square of body height (in meters). less is sometimes used as a diagnostic criterion for the eating disorder anorexia nervosa (Chapter 9).

A meta-analysis from the National Center for Health Statistics, pooling data from studies of nearly 3 million people, found that those with severe obesity (BMI greater than 34.9) had a higher death rate from all causes than did people with normal weight (BMI = 18.5-24.9). However, overweight people (BMI = 25-29.9) had a lower all-cause death rate than normal weight people, and moderately obese people (BMI = 30-34.9) had similar death rates to normal weight people. These controversial results showed that there are problems associated with using BMI to predict health and longevity. Other factors, such as amount of physical activity, level of stress, dietary composition, and social factors, might account for the results.

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Fat percentage varies for people with a given BMI. In the NHANES, for example, people with BMIs less than 25 had fat percentages ranging from 10% to nearly 32%. Factors influencing fat percentage at a given BMI included age, race, gender, and physical activity.

In classifying the health risks associated with overweight and obesity, the NIH and WHO guidelines consider body fat distribution and other disease risk factors in addition to BMI. As described earlier, excess fat in the abdomen is of greater concern than excess fat in other areas. Measurement of waist circumference (see Table 6.1) is one method of assessing body fat distribution, as discussed later in the chapter. At a given level of overweight, people with a large waist circumference and/or additional disease risk factors are at risk for health problems. For example, a man with a BMI of 27, a waist circumference of more than 40 inches, and high blood pressure is at greater risk for health problems than another man who has a BMI of 27 but a smaller waist circumference and no other risk factors.

Thus, optimal BMI for good health depends on many factors; if your BMI is 25 or above, consult a physician for help in determining a healthy BMI for you. While BMI and waist circumference are important measures of health, they must be considered with other factors such as high blood pressure, diabetes, blood fats, and insulin resistance.

Because BMI doesn’t distinguish between fat weight and fat-free weight, it is inaccurate for some groups. For example, athletes who weight train have more muscle mass and thus weigh more than average people and may be classified as overweight by the BMI scale. Because their “excess” weight is in the form of muscle, however, it is healthy. Further, BMI is not particularly useful for tracking changes in body composition gains in muscle mass and losses of fat. BMI also does not take into account differences in gender; women are likely to have more body fat for a given BMI than men. BMI measurements have also over- and underestimated the prevalence of obesity in several ethnic groups, such as Hispanics and blacks, because of racial and ethnic differences in muscle mass and muscle density. Finally, BMI is a poor predictor of health in people short in stature, whose gene function may have been altered by environmental factors early in life. If you are an athlete, a serious weight trainer, or a person of short stature, do not use BMI as your primary means of assessing whether your current weight is healthy. Instead, try one of the methods described in the next section for estimating percent body fat.

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