Experts rate the best and worst in body-fat measurement devices.
Trying to get in shape? Then don't depend on your bathroom scales. To get the most accurate measure of your progress, experts say, you need to track your body fat as well as your weight.
"Most people focus only on losing weight, not on the fat," Cedric X. Bryant, PhD, chief exercise physiologist with the American Council on Exercise, tells WebMD.
"Preserving lean tissue and losing body fat -- that's what you need to strive for," Bryant says. "The only way to know how you're doing is through some form of body-composition assessment."
You know about the old standard measuring tools, like the body mass index (BMI) and the tape measure. And thanks to today's technology wizards, some very good new devices are available to measure your body fat.
To learn which are worth your time and money, WebMD got ratings from Bryant and from two more top exercise physiologists: Megan McCrory, PhD, an energy metabolism scientist with the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston; and Len Kravitz, PhD, senior exercise physiologist for IDEA Health and Fitness Association.
The BMI Test
This is a simple calculation, using the most basic tools -- your height and weight. Plug these numbers into a BMI calculator to learn whether you are obese, overweight, or normal weight.
The BMI was developed using large, population-based studies. Though it doesn't address percentage of body fat or muscle, it helps health care professionals quickly assess which patients may be at risk of health problems linked to excess weight.
The verdict: Free and readily available; good for assessing health risks but doesn't measure body-fat percentage. If you are short, or very muscular, results tend to be less accurate.
"It's a good starting point, a really good way to get a basic estimate of whether you are overweight or not," says Bryant. "BMI tends to correlate pretty closely with health risks associated with being overweight or obese."
The experts' grade: D. "The BMI doesn't give you body fat measurement," says McCrory. "But if gives an excellent BMI measurement!"