BODY WATCH : Survival of the Leanest : Would you rather be pinched, dunked or have an electric current run along your body? Experts say those are the most accurate ways to find out just what percentage of you is made upof--yuck--fat.

I’ve never been fond of tests that you can’t study for, or at least cheat on. Nevertheless, I recently submitted my body for three tests to determine just how much of me is fat.

Body-fat testing is considered to be a helpful measure of health and fitness. It’s not the only measure--you also have to consider cardiovascular fitness, strength and flexibility. But, as health indicators go, it’s a lot more useful than body weight. When you step on a scale, you get the grand total of your fat, muscle, body fluid, bones and connective tissue. This, experts say, is useless information.

“There are a huge number of people who are very low weight but who are very fatty,” says Bonnie Modugno, a Santa Monica nutrition consultant. At the same time, athletes might be considered heavy by traditional standards, when in fact they’re just packed with muscle, which weighs more than fat.

Body-fat tests distinguish between fat and “lean body mass.” So what’s a good score? For women, the optimal range is considered to be 18% to 25% fat; for men, it’s about 12% to 18%. (Experts disagree on the precise numbers.) Studies suggest that women who exceed 30% to 32% fat and men who exceed 20% to 22% fat are at increased risk for such conditions as heart disease, high blood pressure and diabetes.

But, experts emphasize, being too lean (not a problem here) is risky as well. “Once females start dropping below 17% body fat, we start seeing an increased incidence of menstrual period problems,” says Sheila King, coordinator of the UCLA Extension Certificated Program in Fitness Instruction. Erratic or absent periods can lead to a host of serious medical problems such as permanent bone loss.

Experts say you shouldn’t put too much stock in body-fat results because every testing method has room for error and because body fat is only one measure of overall health. “It’s just a tool,” Modugno says. “People can get so neurotic about these numbers.”

With that in mind, I set out to quantify my fat.

Pinch an Inch

First I tried the cheapest and most convenient method of body-fat testing: the skin-fold caliper. A caliper looks, more or less, like a gun with salad tongs attached. When your tester fires, the tongs pinch your skin and a gauge measures the hunk of fat in millimeters. The tester pinches three, four or five points on your body and plugs the results into corresponding formulas that estimate your body fat.

Calipers have a margin of error of about 4%, but the results can be skewed more if the tester pinches too much skin, not enough skin or the wrong site.

I went to L.A. Fitness in Woodland Hills, where I was pinched by Kevin Lewis, president of State of the Art Fitness, the club’s personal trainers. Lewis measured four points on my body: the biceps, the triceps, the subscapular (otherwise known as the hunk of blubber below your shoulder blade) and the suprailiac (the hunk of blubber above your hip).

Don’t get the wrong idea: These pinches hurt--almost as much as when my Aunt Rae would maul my cheek on the holidays. But Aunt Rae pinched me only once or twice a year. Lewis pinched each site three times.

“For accuracy,” he said, at which point I decided Congress should have included skin-fold calipers in the recent ban on assault weapons.

I waited anxiously as Lewis did the calculations. My score: 26.5%. I was less than elated, especially when he handed me a sheet of paper and circled “moderately unacceptable.”

I once showed up for a job interview wearing jeans; that was moderately unacceptable. But my body? My 27-year-old body that bicycles 150 miles a week?

Lewis tested me again, this time pinching three sites on my body. The result: 24.4%. I concluded that the three-site test was more accurate than the four-site test.

Slam Dunk

My search for an even more accurate result led me to the Centinela Hospital Fitness Institute in Culver City for what experts consider the most precise body-fat testing method: underwater weighing. It’s also expensive--about $50--and cumbersome.

You sit on a scale in a tank of water, and your underwater weight is then plugged into a mathematical equation. It’s all based on the premise that muscle sinks and fat floats. Fat is less dense than water, whereas muscle is more dense; the more fat you have, the more your body wants to float when dunked under water. The margin of error for underwater weighing is about 2% to 2 1/2% for young to middle-aged adults. The test is less accurate for children, older adults and extremely lean people.

While waiting for my physiologist to dunk me, I glanced at the TV, which was tuned to “Market Talk” on the Business Channel. “The cash/bond yield is at 7.44% and utilities are up 2.17,” the anchorman said. Then I thought I heard him say, “The Dow is up about 3 1/2% and Suzanne Schlosberg’s body fat is up 8 1/2% after a week of heavy eating.” But I must have imagined that part.

After a few minutes I was greeted by my cheery physiologist, Jim Erwin, director of the institute’s Clinical Testing and Exercise Programs. I followed him to the 6-foot-high cylindrical testing tank--basically a giant version of the pot I boil pasta in.

I slowly climbed the four steps up to the tank, imagining that I was headed for the gallows. Then I stumbled over the ledge and plopped myself onto the clear plastic scale in the center of the tank. The water was hotter than I’d expected--98.6 degrees. Floating in four feet of water, I felt like a giant piece of fusilli .

Erwin told me to blow the air out of my lungs and lean forward until I was completely submerged. “If there’s any air trapped in your lungs, it’ll look like you’re fatter than you really are,” he said. This I did not need. I blew hard. I remained underwater for about five unnerving seconds as my weight registered on the digital scale.

Apparently, however, I hadn’t blown out all my air, and Erwin didn’t get a good reading. He told me to relax for a few moments before trying again. “This is the most accurate method, except for killing someone and peeling off their fat,” he offered while we passed the time.

I dunked a total of five times, weighing an average 1.74 kilograms. I like hearing my weight in kilograms because I have absolutely no idea what it means.

My body fat turned out to be 23.1%. I decided to celebrate with lunch at Gratis, the new fat-free restaurant in Brentwood.

Zap

Since I seemed to be on a roll--having dropped from 26.5% with calipers to 23.1% with underwater weighing--I decided to get my fat tested by another popular method: bioelectrical impedance.

You lie on your back while a signal travels from an electrode on your foot to an electrode on your hand. The faster the signal, the more muscle mass you have. This is because water conducts electricity, and muscle is 70% water. Fat, on the other hand, is just 5% to 13% water. It “impedes” the signal.

Bioelectrical impedance, which costs about $50, is considered to be less accurate than underwater weighing and perhaps more accurate than skin-fold calipers. But, as my tester, nutrition consultant Modugno, explained, the results are often skewed. If you’re dehydrated, the machine overestimates.

For this reason, you’re not supposed to exercise, drink alcohol, take laxatives or consume caffeine for 24 to 36 hours before the test, and you’re not supposed to eat for at least three hours prior.

Modugno taped electrodes to my right foot and hand. I was hoping the signal would zoom through me like a Japanese bullet train. But it traveled more like my mom’s old Chevy station wagon.

“I think the estimate is high,” Modugno said, not offering any number in particular. I didn’t ask. “Let’s do the calipers,” she said.

Modugno pinched five sites on my body, yanking my fat again and again until she was satisfied with the measurement. She said this was more complete than the three- and four-site tests because people store fat differently. Some people carry most of their fat in their arms and legs, she said, whereas others carry more in their torso. Three-site tests generally favor one region or the other.

Using the five-site test, she calculated my body fat to be 23.6%. Only then did she show me the computer printout from the impedance machine, which came up with a score of 27.1. Modugno said I probably was dehydrated.

In reality, she said, my body fat is about average for a woman my age, and it does not necessarily correlate with my level of fitness.

“There’s nothing wrong with average,” she said.

I wasn’t going to argue. It sure was better than moderately unacceptable.