What are you made of? The BOD POD knows all

For many of us, the scale tells all we need to know about our weight. But for some, it's important to know what kind of weight they carry. A lean 220, a flabby 160 or a dangerously skinny 105?

Body-composition testing identifies how much of you is made up of fat, and how much is lean mass (muscles, bones, tendons, etc.). Excess body fat has been found to increase the risk of diabetes, heart disease and some cancers. Lean mass takes up less space, so you'll look better, and muscle burns calories more efficiently, so a trained body continues to reward itself.

Perhaps the greatest benefit of body-composition tests is how they can provide a baseline by which you can direct and measure the progress of future exercise and nutrition programs.

But how to measure?

The Body Mass Index (BMI) calculates a person's weight and height to come up with a number that gives a general sense of where he is in the spectrum between underweight and obese. Go to www.nhlbisupport.com/bmi/, plug in your height and weight and see where you are. The BMI is used a lot, including by some life insurance companies, because it's simple and gives a ballpark picture. It is also inexact, lacks specifics and can be misleading. The BMI also doesn't take into account muscle density. According to the BMI, probably all of the Seahawks are overweight or obese.

Most often, calipers are used to judge body composition by measuring the thickness of subcutaneous fat in various places on the body and then extrapolating the data into an overall fat-to-lean ratio. This is not the most exact method, either, but often reliable enough if the tester knows what he or she is doing. Other testers simply calculate waist girth divided by hip girth. There is also something called bioelectric impedance analysis, which sends a low-level electrical signal through the body.

Hydrostatic weighing — while submerged in water — has long been considered the gold standard, but it's a hard test to perform (and harder to find).

Then there is the lima-bean-shaped BOD POD, which uses air displacement to measure your composition. Data suggest the BOD POD is accurate. It is certainly easy to do. You wear a tightfitting bathing suit and cap and sit still for a couple of minutes as it measures. It also measures your resting metabolism rate, the pace at which your body burns calories just by breathing.

But the BOD POD isn't easy to find, either. There are only six in the state, four of them around Puget Sound. The Washington Institute of Sports Medicine in Kirkland bought the 25th BOD POD ever sold in 1996 and has done more than 6,000 assessments. South Kitsap High School is perhaps the only high school in the nation with one. There is one at the Emerald City Smoothie at North 100th Street and Aurora Avenue North, where I did a test. The guys who run that machine often take it on the road, to health clubs and events.

Within five minutes, I learned the weights of my fat and lean mass and the percentages of my total weight that each represented. I found out where I am on the spectrum, with obese and dangerously lacking in fat at each of the extremes.

David Parker, executive director of the Washington Institute of Sports, says most people of normal weight probably wouldn't gain much from going through the test. But the readings do help those trying to achieve their ideal weight in the healthiest way.

"Some people are given unrealistic weight-loss goals based upon 'weight norms' by age and gender," Parker says. "These people will never succeed in moving toward their real ideal weight, given their bone structure and existing fat and lean mass. Knowing fat and lean mass values as one loses or gains weight allows that person to intermittently change their program to achieve maximal fat loss."

Susan Kleiner, owner of High Performance Nutrition on Mercer Island and author of books on nutrition and athletics, agrees.

"Once I know body composition, I can design a very customized diet," she says. "I can also target exactly how much weight should be lost or gained, based on the percentage-of-body-fat goal.

"Someone might come into my office saying they need to lose 20 pounds, based on some ideal body weight number. But if we measure body fat and it comes out to 27 percent in a young woman, I might help her understand that if she's trying to reach a healthy 20-25 percent body fat, she really only needs to lose 10 pounds or less."

National Institutes of Health recommends body fat of 13 to 17 percent for men and 20 to 25 percent for women. Athletes will have lower body-fat percentages. In general, a man's body fat should not be above 30 percent, and a woman's should not be above 40 percent (5 percent for men and 15 percent for women are also considered unhealthy).

While knowing your percentage can help, it is not a good idea to test if the number will be just one more thing to obsess over or feel guilty about. The last thing you want to do is get hung up on your fat score — unless you're in the danger zones and need a wake-up call.

(For the record: The BOD POD tells me I have 10 percent body fat, which is "lean.")

Richard Seven: 206-464-2241 or rseven@seattletimes.com