Everyone needs some body fat to burn energy and process vitamins. The normal level for women should be about 20 percent, states the President's Council on Physical Fitness and Sports. Women with more than 30 percent body fat are considered obese, according to the council. One-third of U.S. women are obese and another third overweight, notes the National Institute of Diabetes and Digestive and Kidney Diseases, and thus are at risk of coronary heart disease, type 2 diabetes, osteoporosis and other disorders. Reaching a target body fat percentage in the healthy range is an important goal in both individual and public health terms.
Definition
The American Council on Exercise (ACE), with more levels in its analysis of body fat percentages than the President's Council, defines body fat norms for women as ranging from 14 to 20 percent for female athletes, 21 to 24 percent for fit women, 25 to 31 percent as acceptable and greater than 32 percent as obese. ACE recommends that personal trainers help clients to reach lower target body fat percentages by setting a goal of losing 10 percent of body weight or moving from one body-fat classification to the next.
Identification
Researchers use dual energy X-ray absorptiometry (DXA) to precisely measure body fat. This specialized exam provides the ratio between bones, muscle and fat in the body, notes Dr. Edward R. Laskowski, writing for MayoClinic.com. Other methods include underwater weighing and an air-displacement device sometimes known as a Bod Pod. These methods provide more accurate information on your body fat percentage than body fat analyzers, also called impedance meters, available at health clubs and as a feature in some home weight scales, which may be thrown off by how hydrated you are.
Significance
Although the United States and other countries use the body mass index (BMI) as the standard measure of obesity, the fact that BMI varies in its relationship to body depending on age, sex, ethnicity and physical conditioning puts limits on the usefulness of BMI studies. DXA can provide "a more accurate measure of body fat," note Dr. Lori G. Borrud and colleagues at the National Center for Health Statistics in a report published in 2010, "Body Composition Data for Individuals 8 Years of Age and Older: U.S. Population, 1999-2004," released as part of the National Health and Nutrition Examination Survey.
Expert Insight
The National Health and Nutrition Examination Survey for 1999-2004 found that that the mean body fat percentage for U.S. women is 39.8 percent, with girls aged 8 to 11 carrying the lowest mean, 31.9 percent, and women aged 60 to 79 the most, 42.4 percent. For women aged 20 to 39, white women carried 37.3 percent body fat; black women, 38.8 percent; and Mexican-American women, 39.6 percent.
History
An earlier National Health and Nutrition Examination Survey conducted from 1988 to 1994 also found women far above the recommended body fat level of about 20 percent, but not as fat as the 1999-2004 survey. Of women aged 20 to 39, white women carried 33.0 percent body fat; Mexican-American women, 37.8 percent; and black women, 38.5 percent. This earlier survey used bioelectrical impedance rather than DXA to measure body fat.
References
- The President's Council on Physical Fitness: Exercise and Weight Control
- National Institute of Diabetes and Digestive and Kidney Diseases: National Statistics Related to Overweight and Obesity
- American Council on Exercise: Percent Body Fat Calculator
- MayoClinic.com: How accurate are portable body fat analyzers?
- National Center for Health Statistics: Body Composition Data for Individuals 8 Years of Age and Older
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