Beyond BMI

At the University of California, Berkeley, athletes are measured a minimum of three times a year and then coached on nutrition and given specialized workouts. 

Suzanne Nelson, sports nutritionist for the California Golden Bears, says that knowing an athlete’s body composition is vitally important.

“It’s especially good for women because coaches want female athletes to gain muscle, but to a college girl, weight on the scale? No, no, no,” she said. “When evaluating an athlete, I want to see if the weight loss is from body fat loss or lean muscle loss.”

When it comes to the health of the 800 or so Cal athletes she sees every year, merely computing their height and weight with a body mass index, or BMI, formula won’t do. This is true for the smallest gymnast, as well as the largest linebacker.

“In general, we don’t have good measurements for body composition for height and weight,” Nelson said. “And then you look at the charts and they’re all antiquated.”

But athletes aren’t the only ones who need to watch their weight. An estimated 35 percent of Americans are considered obese, and there’s increasing focus on slimming down through diet and exercise.

With an increase in inexpensive diagnostic technology on the horizon, more patients trying to maintain their weight could soon be getting the same personalized attention.

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What's Wrong with BMI?

BMI was first developed in the 19th century by Belgian mathematician Lambert Adolphe Jacques Quetelet, and little has been changed from the original formula. To British mathematician Dr. Keith Devlin, using BMI to determine health is an embarrassment to the U.S.

“It is embarrassing for one of the most scientifically, technologically, and medically advanced nations in the world to base advice on how to prevent one of the leading causes of poor health and premature death on a 200-year-old numerical hack developed by a mathematician who was not even an expert in what little was known about the human body back then,” he told NPR

While useful for judging a population’s overall obesity rate, BMI is not very effective on a personal level. It fails to take into account a person’s bone density, waist size, age, race, and other important factors to determine obesity.

“Besides muscle, bone density is a big wild card,” Nelson said.

And highly trained athletes are at a greater disadvantage: their excess muscle typically puts them at a higher BMI, so they may actually be considered obese.

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Why Accuracy Matters

Calvin Torres, a sports science coordinator at Cal, stands 5 feet, 10 inches tall and weighs 158 pounds. Though his BMI is 22.7, which puts him in the “normal” category, that number isn't a very helpful guide for nutrition and exercise.

With more precise diagnostics, however, Torres and others at the Berkeley sports lab can get a better understanding of their body composition. Torres, for example, has 134 pounds of lean muscle and 24 pounds of fat.

Those results came from two different diagnostic systems in use at Cal: the Bod Pod and the InBody720 Body Composition Analyzer.

The Bod Pod—which resembles a spaceship's escape pod—is a form of air-displacement plethysmography also used at the White House to monitor the health of the First Family and staff. A person wears spandex underwear and a swim cap and enters the sealed compression chamber to be analyzed.

But the Bod Pod has its limitations. The chamber is small, meaning that larger people may not fit inside comfortably, and it may be a nightmare for the claustrophobic. With calibrations and testing, the task takes about 20 minutes per person, which is time-consuming.

The staff continues to use it, however, because it’s the same technology the National Football League’s scouts have used for the past eight years. This way, Cal football players entering the draft are familiar with how the testing works.

The preferred measuring device for Berkeley staffers is the InBody720, a form of Bioelectric Impedance. The test takes about two minutes as a comfortably dressed person stands on metal pads and grips two handles. A low level electrical current goes through their body providing detailed results, including breaking down a person's weight by arms, legs, and trunk.

The results only provide a snapshot of a person’s health, but when used over a period of time the machine can help track important changes, such fat loss and muscle retention.

“They’re really useful in getting a more complete picture,” Nelson said.

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