Body-Fat Calculators Weigh In

Southern Californians are hooking up to some unusual machines these days in the name of fitness.

They are shooting beams of infrared light into their biceps or allowing electrodes to be attached to their hands and feet. They are plunging underwater on a cadaver scale or enduring the humiliation of having their “love handles” squeezed by a stranger wielding calipers.

All of these procedures measure body fat, and they have become popular offerings in some Southern California health clubs, weight-control centers and wellness clinics.

“When I do fitness testing, (body fat) is the issue that everyone wants to talk about,” said Ellen Turkel, a consultant for corporate wellness programs and health clubs. “You can talk about flexibility until you’re blue in the face, but when you start talking about body fat, they’re on the edge of their seats.”

Experts caution, however, that as testing and new machinery proliferate, so does the chance of getting inaccurate or misleading results. They urge anyone undergoing body-fat tests to consider the skill of the test-givers, pretest conditions and equipment limitations for each of the five most common techniques.

“I think that high-tech gets a lot of publicity because it looks exciting and because people who are trying to sell products are pushing them,” said Paul Schmidt, a fitness specialist with the city of San Diego. “But things are misused quite often.”

Body fat isn’t all evil. Layered under the skin and packed around organs, fat insulates the body from cold, cushions it against injury and supplies it with essential everyday fuel.

Too much body fat, however, increases a person’s risk of hypertension, diabetes and high cholesterol, among other problems.

A study done at San Diego’s Naval Health Research Center, to be published this year, concluded that men with more than 22% fat and women with more than 33% fat are at significant health risk.

Beyond that, “ideal” body fat percentages vary. Depending on whom you ask, a healthy rate for men ranges anywhere from 6% to 25%, while a healthy woman’s body fat can range from 9% to as high as 32%.

Health clubs and wellness centers that test body fat typically use one of five procedures: the old standards of underwater weighing, skin-fold calipers and circumference equations and the newer infrared technology and bio-electrical impedance machines, which conduct low-level electricity through the body.

Last summer, Schmidt compared the five procedures in a study on 75 police officer trainees--a primarily young and relatively fit test population. His results rated skin-fold calipers as the second most accurate method behind underwater weighing, the “gold standard” of body-fat testing. Circumference equations came in next, followed by the infrared technique and, finally, the bio-electrical impedance.

Tim Lohman, a professor and researcher in the University of Arizona’s department of exercise and sports sciences, ranks the methods differently, based on studies with participants more typical of the average population.

He says impedance, “if the machine is reliable,” and skin-fold calipers, if the tester is well-trained, come in second to underwater weighing. Circumference measurements are third. Infrared, which is so new that it hasn’t been widely tested in independent studies, is the least reliable, he said.

What follows is a rundown on each of the five testing methods.

* INFRARED: The infrared machine, marketed under the name Futrex 5000, is an outgrowth of U.S. Department of Agriculture research on pig fat. It operates on the premise that fat refracts light differently than muscle and bone do.

Using a wand attached to a small hand-held microprocessor, the instrument shoots a beam of infrared light into the body halfway between the shoulder and elbow on the biceps of the person’s dominant arm. Manufacturer Futrex Inc., of Gaithersburg, Md., claims that fat measured here is directly proportional to total body fat.

The infrared light beam passes quickly through fat, then bends as it hits muscle and bone. The machine calculates percent body fat as it measures that bend.

The Futrex machine costs about $2,000, according to Tori Tunnell, sales manager for the company. He said that individual tests, while most often included in a comprehensive body-composition analysis and wellness screening package, can cost as little as $15.

The Los Angeles Rams have included the machine in their body-fat testing equipment. But the team uses the machine for spot checking all over the body, according to Garrett Giemont, the team’s strength trainer.

Operators of the Futrex 5000 liken it to a blood pressure test. There is no need to remove clothes, lie down, be dunked under water or meet pretest conditions, they say. The instrument also allows for self-testing.

But Anita Jones, health promotion director for Accents on Health, a San Diego wellness clinic, said the machine isn’t nearly as easy to operate as its instructions indicate. To find the right spot at the “belly” of the biceps takes a lot of practice, she said.

Lohman said that although he hasn’t yet tested the machine, one of its limitations is that, unlike the other methods, the manufacturer suggests only one measurement location to determine total percent body fat.

Another concern, exercise physiologists say, is that the infrared light beam shoots only a limited distance into the body, and that could affect the accuracy of measurements on obese people.

But a company spokesman says the depth of the light beam is accounted for in the machine’s software and that the beam is but one of the variables entered into the software’s equation that determines percent body fat. Other variables include activity level, height, weight, gender and body frame.

* BIO-ELECTRICAL IMPEDANCE: The bio-impedance method, out for about four years, measures resistance to electricity to determine percent body fat. Operators attach two electrodes each to specific locations on the foot and hand through which they introduce a low-energy, high-frequency electrical current.

Lean muscle, which has high water content, easily conducts the electricity, while fat resists. Measurement of that resistance predicts the body fat percentage.

Valhalla Scientific, a San Diego-based company, is one of the industry’s top two manufacturers of the machines, which cost between $2,500 and $5,000.

Some exercise physiologists point out that many variables can affect body fat measured with this equipment. When a person last ate, drank and exercised can influence results of the test, which costs from $40 to $100.

“It’s hard to get reliable measurements,” said Turkel, the corporate wellness consultant.

But, she added, “I think they’re on the cutting edge, and in the next few years, people will be considering it more seriously.”

Valhalla’s operation manual cautions that to ensure accurate test results, the following conditions should be avoided: participation in heavy exercise within eight hours of the test; water loss or dehydration due to hot weather, exercise or inadequate fluid intake; consumption of excessive quantities of food within six hours of the test, of water within four hours, of caffeine within three hours, or of alcohol within 48 hours; fasting within 72 hours of the test; using the bathroom more than an hour before the test, and excessive water retention during the three days before a woman’s menstrual period and seven days afterward.

Valhalla trains anyone who buys the equipment to observe the pretest conditions, Clark said. “Proper medical procedure is like any other test.”

* SKIN-FOLD CALIPERS: Skin-fold calipers, developed in the 1930s to measure the fat content of pigs on their way to market, are perhaps the best known devices used to measure body fat.

Operators use a plier-shaped apparatus--one of a dozen types--to pinch flesh in three or more body locations. Readings are correlated with an equation that takes into consideration a person’s gender, height, weight and age. The equations are particular to specific calipers.

“I’m not old-fashioned, but the old-fashioned calipers really seem to work,” Turkel said. “It’s done on so many people that they’re quite reliable.”

Nationally, the YMCA has used calipers to measure body fat for several decades, said Don Hanna, who sits on the organization’s national program development committee. Though the Y recently has been “deluged” by companies selling newer machines, corporate researchers have decided to stick with calipers for the foreseeable future, he said.

Although the test is simple enough for the recipient, experts say the procedure is frequently mishandled by untrained or inexperienced operators. When that happens, the average error rate can rise to as much as 10%.

* CIRCUMFERENCE MEASUREMENTS: After considering the use of skin-fold calipers to test its personnel nationwide, the Navy went with circumference measurements. According to Jim Hodgdon, a Naval Health Research Center program director, results are generally as good as skin folds and the method is much more easily taught to operators.

Simple, tape-measured dimensions--such as a man’s neck, abdomen and height--are plugged into equations similar to those for calipers. Results have generally been on a par with skin folds, often with less of an error margin, said Schmidt.

“It’s as accurate as anything else,” he said. “These are numbers that are very practical, and people can relate to them. I strongly suggest a move back toward use of circumference measurements.”

* UNDERWATER WEIGHING: Using the principal that fat floats, while muscle and bone sink, underwater weighing actually measures the amount of water your submerged body displaces. That figure helps estimate body density, which in turn predicts percent body fat.

Underwater weighing is certainly the most inconvenient of techniques. Typically, only a few hospitals, universities and athletic teams have the equipment. (Tests cost about $50 to the public.) To be tested, a person must don a bathing suit, balance on what has traditionally been a cadaver scale, exhale all of his or her breath and hold it out for as long as possible underwater, repeating the procedure six or seven times.

“It is not practical for most settings,” Turkel said.

Though other methods gauge their accuracy by hydrostatic body-fat measurements, the technique isn’t without its own errors, fitness experts say. Consider the results logged for several world-class athletes: less than 1% body fat.

Researchers say that occurs because the method assumes the same muscle and bone density for everyone, regardless of ethnic, gender and age differences.

“That can’t possibly be true,” Carter said.

For most accurate results, residual air volume--or the air left in your lungs and esophagus also must be measured.

Regardless of the method chosen, experts urge common sense in dealing with body-fat test results.

Caloric restrictions and aerobic exercise are the only ways to reduce body fat, though weight reduction doesn’t automatically mean a reduction in fat.

And there’s no such thing as spot reducing.

“Can I lose it off my thighs or off my tummy?” Carter said. “The answer is, in general, no. You lose it overall.”

Carter and other experts also counsel those rushing to measure body fat not to place too much emphasis on a small aspect of overall wellness.

“People are taking these things very seriously these days--a little too seriously,” Lohman said. “So many people are so dissatisfied with their (results) but are in a very healthy range.”

Said Schmidt: “We get too hung up on our body-fat assessment versus looking at the big picture of health and wellness and life style. When body fat preempts that, we’re missing the point.”