DUNKED: A FIX ON FAT
Finding Out Your Body Fat Percentage, and Other Scary Tales
by Marc Bloom
"Okay, time for a dunking," Zeb Kendrick announced.
After parading around skittishly in my skimpy, bun-hugging Speedo bathing suit, I was ready to plop my 5'9", 155-pound body into a hydrostatic pool at the Temple University biokinetics laboratory in Philadelphia. I'd come to find out my body fat measurement and consult with Kendrick, director of the lab, who advised people on staying healthfully trim.
I was 52 years old and, I felt, in decent shape. But over the years, I'd continually downsized my exercise intensity, from high-performance racing to easy-does-it recreation. Though I still worked out daily, I could not be sure if I was burning enough calories, and was worried that the jelly roll growing around my waist suggested a health concern.
For hydrostatic support, I brought along my swimming buddy Harry. Big mistake. Harry, 55, has the waist of a runway model. When we go out for lunch after a workout, Harry nibbles on a plain bagel (hold the cream cheese) while I gobble a tuna sandwich (plenty of mayo). "What are you so nervous about?" Harry asked me. Oh, nothing. I'm just standing around practically naked waiting for my love handles to be appraised.
Out of vanity, I had not eaten that morning. I'd given Harry a Powerbar to have ready for me after the test. He held it in view like a reward for a lab rat. I really had to perform.
It had been 20 years since I'd had my fat measured, and then I was burning plenty of calories running marathons. Now, jogging a few miles here and there while also doing bicycling and swimming, I wanted to undergo the most accurate measurement possible: hydrostatic weighing.
"The gold standard," Kendrick called it.
Body fat level is one of the best indicators of good health. Kendrick said excess body fat was associated with diabetes, heart disease, hypertension, gall bladder problems, arthritis and other ailments. As many as one-third of Americans were dangerously overweight, and a study by the Center For Disease Control indicated that only 18 percent of U.S. adults were free of all risk factors of heart disease.
Many people who are sedentary or eat poorly see their body fat levels rise with age. On average, people lose 3 to 5 percent of muscle mass every decade after 25; and past 50, muscle can really take a dive. For every pound of muscle loss, we burn 50 fewer calories per day. No wonder my jelly roll was sprouting like backyard basil after a good rain.
Body fat tells you more than weight alone because it's a precise, personalized measurement. Your bathroom scale (assuming it's even accurate) does not take body type into account. For example, someone with a broad frame might be considered "heavy" but have a desirable fat level. In my own case, I hadn't gained weight but, with years, seemed to have gained fat.
It was comforting to learn that a healthy body fat level was accessible. For men in their 40s, said Kendrick, a level of 25 percent and higher was cause for concern; for women of that age, it's 30 percent and higher. Kendrick's standard was consistent with guidelines of The American College of Sports Medicine (ACSM). Based on data compiled at the Institute for Aerobics Research in Dallas, ACSM tables showed averages of 21 percent (men) and 26 (women) for people aged 40-49.
Before my dunking, Kendrick measured my fat with a pair of calipers, in what is known as skinfold analysis. This is the most readily available method of measurement, and a service offered by many health clubs (see sidebar). With the calipers, Kendrick pinched my chest, abdomen and thigh. Women are measured at the triceps (back of upper arm), thigh and hip. Kendrick withheld my skinfold score until after the hydrostatic weighing. Why spoil the fun?
At Temple, the people tested regularly by Kendrick included military personnel and professional athletes like Philadelphia 76ers basketball players. Great--I'd be compared with drill sergeants and power forwards. Not to mention Harry, who'd once tested under 10 percent elsewhere and walked around the Temple lab like he owned the place.
Any subjects who didn't measure up, said Kendrick, were given a program of diet and exercise to lose fat. For example, if a 40-something woman showed 30 percent body fat, she'd be asked to reduce calories by 10 to 15 percent and do exercise like brisk walking four to five times a week. Her goal, said Kendrick, would be a weight loss of 2-3 pounds per week for the first two weeks; after that, a loss of 1 pound per week was prescribed.
Just about every fitness expert, including those at ACSM, now recommended weight training along with aerobic exercise as essential to good health. Weight-training (sometimes called "resistance" training) converts fat to muscle and increases bone density, reducing risk of osteoporosis. Studies at Tufts University, for example, showed that women aged 50 to 70 who did weight-training twice a week for a year became 75 percent stronger. They'd gained muscle and lost fat, according to Dr. Miriam Nelson of Tufts. Heeding those results, I'd begun weight work myself and could see a difference in muscle tone.
Like a student waiting for his SAT score, I finally stepped into the hydrostatic tank, set at a bathlike temperature of 91.5 degrees. Kendrick explained that essentially my weight in air would be subtracted from my weight in water, using a formula devised at the University of Minnesota after World War II. Kendrick had me rub down my body to get rid of air bubbles, then position myself on a Chatillon scale so that the water was chin-high. The scale looked like the kind found in a butcher shop to weigh a side of beef.
For accuracy, the air in your lungs (called lung volume, or "vital capacity") must be expelled. To achieve this, Kendrick instructed me to lean forward, submerge my head in the water and exhale as fast and hard as I could. I had to repeat this procedure several times. "Blow out the candles," hollared Kendrick, like a coach rallying his athlete.
It wasn't easy. I had to hold each exhale for five or six seconds, but it seemed much longer. From my swimming, I was comfortable in the water, but with all the gadgetry and people poking their noses into the room, I felt like some specimen being sacrificed for the greater good.
I emerged from the tank, toweled off, got dressed and waited for Kendrick to do his computation. Harry fed me the Power Bar and looked at me approvingly, as though I'd taken a risk and come out alive. Well, there was some risk involved. I wanted to think of myself as healthfully thin, was proud of my 31-inch waist and had resisted the idea that I might not be perfect.
I guess I had a "perfect problem." It turned up in my work, in how I fussed around the house, even in my appearance. I was vulnerable to the cultural imperative to be impossibly lean. I got swept up in the no-fat, low-fat craze. Did I really need to have non-fat yogurt instead of real ice cream? At least I still had mayo with my tuna. Talk about living on the edge.
A sports dietitian, Nancy Clark, based on Brookline, Massachusetts, had advised me to work on eliminating fat-guilt. "You need fat in a balanced diet," said Clark. "Food is one of life's pleasures. You don't have to have a 'perfect' diet to have a good diet."
Clark made perfect sense, and now I waited for Kendrick's verdict. First, Kendrick delivered the skinfold measure: 15.5 percent. That was better than the skinfold score I got as a 32-year-old marathoner. And since skinfold results typically read a few points higher than hydrostatic measures, I was feeling relief.
Then came the big one--the result for which I'd consented to expose my body before scientists accustomed to scrutinizing the pros. Hydrostatic weighing. Okay, lemme have it . Kendrick gave it to me straight: 12.8 percent. Oh, the joy! While not pro basketball level, that figure put me in the "superior" category for people my age. The score affirmed my good health and, most importantly, validated my low-intensity exercise program. It also meant I would start taking Clark's advice to worry less about fat and feel more comfortable with my body.
It was time to take off my bathing suit and go for some ice cream.
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Sidebar: Getting a Body Fat Test
There are four reliable methods of body fat testing, according to Zeb Kendrick, Ph.D, director of the Temple University biokinetics lab in Philadelphia.
1) Skinfold Analysis : A pair of calipers is used to "pinch" three parts of the body where fat accumulates. For an accurate reading, the calipers must be scientifically authentic and come with a spring-loading mechanism that squeezes at a constant pressure. Checking with the many health clubs that offer body fat testing, using calipers, for a modest fee like $25. Make sure the person doing the test has experience and knows how to use calipers properly.
2) Hydrostatic weighing : This is the most accurate measure, in which the subject is placed in a specially designed pool, and your weight in air is subtracted from weight in water. But this test is rarely available at health clubs and only at a small percentage of college laboratories nationwide. If my can find one, the cost is reasonable. Temple University charges $60.
3) Bio-Electrical Impedance : Electrodes are placed on a person's ankles and wrists and a small current is passed through to measure resistance to the current and produce a figure for fat-free mass. A result of 80 percent for fat-free mass means the person has a body fat level of 20 percent. For accuracy, it's important for the subject not to be dehydrated, or over-hydrated, because too little or too much water in the system can offset the measure. The accuracy, and cost, is about equal to skinfold analysis. Some health clubs offer this service.
4) Infrared Reactance : A fiber-optic probe is positioned at the biceps (front of upper arm) and a beam of infrared radiation is passed through. The reflected energy is used to obtain a body fat measurement. Since only one part of the body is used, the result is not as reliable as the other methods, according to Kendrick.
Products like "fat-o-meters," "body fat analyzers" or "body fat scales" found in drug stores and supermarkets do not produce valid results. There is too much variation for error since these devices have not been tested with large populations. "They deliver ballpark figures," said Kendrick. "Not a tight fit."
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