Q: I am a 56-year-old woman. At my gym they use calipers to measure body fat, but my body fat registers 9 percent lower on my Tanita scale. Why?
– Peggy Maday, Denver
A: It has become clear that it is fat loss – not weight loss – that defines good health and reduces risk of obesity-related diseases.
Because the only way to calculate body fat with 100 percent accuracy is through a postmortem, we must be satisfied with less-accurate methods that yield ballpark results.
The easiest and cheapest is performed with calipers, which measure skinfold thickness from three to seven locations around the body. The accuracy is dependent upon the skill of the caliper operator, the quality of the calipers and the sites measured.
Different sites are chosen for women and men because of the different areas of fat storage attributed to gender. (Yes, age is a factor. As we age we tend to store more fat, which is why the “normal and healthy” percentage for body fat goes up on the reference tables.)
The caliper method assumes that 50 percent of our body fat is under the skin with the rest located around organs and in muscle tissue. This method may not, therefore, be valid for some populations. Genetics, exercise levels, eating habits and extreme obesity are factors that skew results. Also, there are more than 100 equations used to compute the numbers, and their accuracy can be off by as much as plus or minus 6 percent.
Tanita, Homedics and Taylor are among manufacturers of bathroom scales that measure body fat. First, you enter your age, gender, height and activity level into the unit. Then you step on the scale barefoot, and a low level electrical current, carried by water, travels through the body. The scales measure where water is not located (fat does not store water) so good hydration is crucial for accuracy.
The Tanita scale is the most well-known because the company was the first to enter the home-use market. Prices range from $90 to $120. They can measure body fat, hydration levels, bone density and even metabolic age.
Homedics/Taylor’s scales, at about $80, offer body fat and hydration measurements along with calculations of the number of calories required to maintain or lose weight.
The choice comes down to personal preference because all are excellent products. The accuracy of these scales can be as close as plus or minus 3 percent.
Accuracy is dependent on the user’s ability to duplicate conditions almost exactly each time the scale is used.
Dehydration, exercise or eating before measuring, prescription drugs, caffeine, alcohol and menstrual cycles all can affect accuracy.
Linda Buch, ACE-certified exercise specialist, will respond to fitness questions only in her weekly column. Send questions to: Body Language, The Denver Post, 1560 Broadway, Denver, CO 80202 or LJBalance@aol.com.
