"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
The experts' grade: D. "The BMI doesn't give you body
fat measurement," says McCrory. "But if gives an excellent BMI