Women are classified as having an unhealthy amount of body fat by the American Council on Exercise and the YMCA at levels above 32 percent. Precisely determining this figure has become of more importance, particularly if you are in your 50s and 60s. Many women in these age cohorts have became heavier in national surveys conducted after 1980, such that their average body fat of 30 to 31 percent comes pretty close to this risky boundary.
Types
Underwater weighing serves as the “gold standard” of determining body fat percentage, notes the Department of Kinesiology and Health at Georgia State University. But it may only be available at research universities. Dual-energy x-ray absorptiometry, which is a low-dose X-ray known as DXA or DEXA, provides an extremely accurate calculation of a your body fat percentage, as well as your fat-free mass and bone mineral content. You lie on a flat bed for about 10 minutes while machine scans your body. A DEXA scan looks at the entire body’s composition as well as that of the arms, trunk and legs. Universities and health care providers offer DEXA as well as an fat calculator that works by air displacement called the Bod Pod.
Considerations
Cheaper but less accurate alternatives to calculate body fat percentage include portable analyzers based on bioelectric impedance, skin-fold measurements and rough calculations using measurements of the waist, as well as the Body Mass Index based simply on height and weight. Many health clubs and even home weight scales include metal foot plates to measure body fat percentage by bioelectrical impedance, but Georgia State University and the Mayo Clinic warn they may not be accurate.
Costs
Hydrostatic weighing costs $20 to $75, the Bod Pod measurement runs around $20 and a DEXA scan costs $200 but may be covered by health insurance, especially for older women eligible for osteoporosis checks. Skinfold calipers cost $10 to $600 as of May 2010, according to AsktheTrainer.com.
Warning
While free and easy to perform, BMI works better as a screening tool than a diagnostic tool, the Centers for Disease Control and Prevention notes. It can misdiagnose you as overweight if you are fit and muscular, for example. The Baylor College of Medicine and the University of Houston also found in 2009 that BMI overestimates the number of African-American women with obesity and underestimates the number of Hispanic and Asian women who are obesity, based on DEXA scans of a sample of women crosschecked with BMI predictions.
Function
You set a healthier target body fat percentage and calculate what your weight should be to meet that percentage. For example, notes the University of Nevada Extension Service, let’s say you are 47 years old and weigh 170 lbs. with a body fat percentage of 30 percent. You want to attain a healthier body fat percentage of 25 percent. Multiply 170 lbs. by 30 percent to note your fat weighs 51 lbs. Subtract the fat weight from your overall weight to find your lean weight, which is 119 lbs. Since you want only 25 percent of fat weight, divide 119 by 75 percent. Your result, a target weight of 158.7 lbs., would consist of only 25 percent body fat.
