ACSM'S Health & Fitness Journal:
Thompson, Dixie L. Ph.D., FACSM
Dixie L. Thompson, Ph.D., FACSM, is the director of the Center for Physical Activity and Health and an associate professor in the Department of Exercise, Sport, and Leisure Studies at the University of Tennessee, Knoxville.
The prevalence of obesity has increased dramatically in recent decades. Thirty percent of American adults are now classified as obese, and nearly two thirds fall into either the overweight or obese category. Many diseases including heart disease and type 2 diabetes are linked to obesity. Researchers debate the number of deaths caused by obesity, but even the lowest estimates suggest that more than a hundred thousand deaths in the U.S. each year can be attributed to obesity. The economic burden of obesity is staggering. Nearly $100 billion dollars are spent each year on medical costs associated with overweight and obesity. Described below are some simple tools individuals can use to determine if they are obese.
Symbol Body Mass Index
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Different criteria can be used to determine if a person is obese. The most common is body mass index (BMI). BMI is a value reflective of the relationship between height and weight. To calculate BMI, use this formula:
The recommended BMI range is 18.5 to 24.9. Overweight is defined as a BMI of 25 to 29.9, and obesity is a BMI of 30 or higher. Numerous studies have demonstrated that disease risk is considerably higher and early death is more likely for individuals who have a high BMI.
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Symbol Waist and Hip Measurements
When people gain weight, fat is deposited in a pattern largely determined by genetics. Abdominal obesity is a condition in which excessive fat is located in the trunk area. This condition is particularly dangerous because of its link to chronic diseases. Measuring waist size is one way to determine the presence of abdominal obesity. The measurement should be taken against the skin (not over clothing), and it is best to have someone take the measurement. Keep the tape measure horizontal and place it around the body at the narrowest part of the waist between the navel and the bottom of the rib cage. Abdominal obesity begins at a waist size of 40 inches in men and 35 inches in women.
Another method for determining abdominal obesity compares the relative size of the waist and hips. This is called the waist-to-hip ratio. For this technique, use the measurement of the waist as described above and divide it by the hip measurement. For the hip measurement, stand with feet together and place the tape around the widest part of the buttocks. A waist-to-hip ratio of ≥0.95 for men or ≥0.86 for women is considered too high.
Symbol Which Measure Is Best?
For most people, all of these techniques are valuable tools for determining obesity. However, for a very muscular person, the BMI score may fall into the overweight category even though body fat is low. For this type of person, waist size or waist-to-hip ratio would be a better choice to determine if abdominal obesity exists. Additionally, fitness professionals can perform other tests that will provide information about how much of a person's weight is composed of fat tissue. These additional tests can be very useful in setting weight loss goals.