Michael Mawicke's bulging biceps make it easy to believe he can bench press 450 pounds. He claims a string of bodybuilding titles and trains others to become more fit.
The percentage of fat on his body is that of a top athlete _ somewhere between 6 and 8 percent.
Just at the moment, he's trying to gain weight.
And yet, according to the most commonly used weight standard in the United States, Mawicke is far too hefty. Not just fat, but obese.
"Severely obese," chimed in Mawicke, 43, a trainer at Gold's Gym who lives in Clearwater.
At 6 feet tall, Mawicke weighs 255 pounds. That gives him a body mass index, or BMI, of 34.6 _ well above the standard of 30 that the federal government considers obese. The government says that Mawicke is at higher risk of contracting heart disease, diabetes and a host of other diseases.
Mawicke, however, feels just fine.
As American health officials focus more closely on the nation's weight problem, body mass index has gotten more and more attention. It is the most commonly used weight statistic in the country, and the basis for the oft-repeated line that two-thirds of Americans are overweight.
But what does it mean? And how good a measure is it?
Many doctors and health researchers say it's accurate, easy to calculate and makes it easier to compare different medical research studies.
"BMI is like a gas gauge in a car," said Dr. Peter Vash, executive medical director of Lindora Clinics in southern California and secretary of the American Obesity Association. "It gives you a pretty accurate estimate of where you are. The question is: What are you going to do about it?"
Other experts complain that BMI gives a misleading picture to many people. It tells some fit people they are fat. It also fails to show that some fat people need to lose weight. Dr. Tim Church, medical director of the Cooper Institute, a Texas nonprofit center that studies physical activity in health, called BMI "a bizarre measure."
"It's widely accepted and run with, but it's really not the best tool," he said. "It's great for epidemiological studies, but for individuals, it's not so valuable."
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Body mass index is a simple measure: a single number comparing weight to height. It was developed in the 1800s by French statistician Adolphe Quetelet. Originally, it didn't measure obesity.
It has been used for decades by researchers tracking weight in medical studies. But some studies used other measures, and most people looked elsewhere, such as at insurance industry weight tables, to see if their own weight fell within the range considered normal.
But in recent years, as scientists have tried to document the health risks of obesity, BMI has become more widely used. In 1998, an influential panel of the National Institutes of Health adopted the standard that federal officials now use: a BMI of 25 or above is overweight; a BMI 30 or more is obese.
Those numbers aren't meant to be arbitrary figures, but the levels at which people have a greater risk for health problems, such as heart disease and diabetes, because they weigh too much.
"It was sort of a call to action for health care providers to look at clients' BMI," said Karen Donato, coordinator of the Obesity Education Initiative at the National Heart, Lung, and Blood Institute and executive director of the 1998 panel.
BMI has definite advantages. Chief among them: It's easy to measure. All it requires is a person's weight, height, and a little math.
"It's highly associated with total body fat," Donato said. "When you can't do a total body fat measurement in an office setting, this was an easy way for clinicians" to measure.
People with a higher percentage of body fat have greater health risks. But measuring body fat requires pricey equipment or special training to use such tools as calipers, and methods aren't always correct.
"The basic problem is it's very difficult to actually measure body fat, and it's very easy to measure weight and height," said David Freedman, an epidemiologist who studies obesity with the federal Centers for Disease Control and Prevention.
BMI also is an excellent way to measure whether children are overweight, said Dr. Frank Diamond, a pediatric endocrinologist at the University of South Florida and All Children's Hospital in St. Petersburg. Children, after all, keep growing. As their weight and height increase, BMI makes it easier to chart whether their gains are appropriate.
"At least in children, I think it's essential," Diamond said. "Because you have this moving target."
But then there are the problems. The most often heard: BMI tags too many muscular people, such as Mawicke or even actor Tom Cruise, as overweight.
"I would have to lose all my muscle mass," to be considered a healthy weight using BMI, said Scott Crowell, a personal trainer and cycling instructor at Lifestyle Family Fitness in St. Petersburg. "I think the BMI charts are off. They need more scrutiny."
Even strong BMI proponents say it's a faulty measure for muscular people. But too much has been made of that failing, Donato said.
"That's gotten too much attention," she said. "Sixty-five percent of Americans fall in the category of overweight or obese, and it's not because of too much muscle."
Crowell said it's not a small problem. A St. Petersburg firefighter, Crowell said he has seen colleagues who need to lose some weight dejected after doctors have told them to lose much more _ say 80 pounds, rather than 20 or 30.
"I think it backfires, because they get too discouraged," he said.
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BMI has a lesser known, but potentially more dangerous problem. It can fail to identify people with levels of body fat high enough to create health risks.
"People below a BMI of 30 can easily be fooled into thinking everything's okay and their risk level is low," said David Frankenfield, chief clinical dietitian at Penn State Milton S. Hershey Medical Center. "BMI tells you if you're overweight, but it doesn't necessarily tell you if you're overfat."
Frankenfield knows this because in 2001, he and colleagues published a study comparing patients' BMI to their body fat. All the people in the study with an obese BMI, over 30, had levels of body fat that would also label them obese _ over 25 percent for men and 30 percent for women.
But of the patients with a BMI below 30, 30 percent of the men and 46 percent of the women still had body fat high enough to label them obese, and to carry significant health risks with it.
Those high levels of body fat were found in men with a BMI as low as 22.6 and women with a BMI as low as 20.1 _ both well within normal BMI levels.
BMI also doesn't look at where people carry fat. Belly fat is a greater health risk than fat on the thighs and buttocks. That's why federal guidelines say doctors should measure patient's BMIs, but also their waist circumference and other risk factors, such as high blood pressure, Donato said.
Nor does BMI measure whether fat is under the skin or what's called visceral fat, which is located deep in the body, around the organs, and again considered more dangerous.
Taken together, Church said, BMI has several flaws and pushes people to look too much at weight and not enough at their body composition and fitness level.
"We're so obsessed with BMI," he said. "It can give you a false sense of security. On the other hand, it can paint a doomsday picture which is not true."
But others say presenting people with a simple, objective measure can motivate them to change. Donato recently watched an episode of The Biggest Loser, the dieting contest reality show, and was struck by how surprised the contestants were when presented with lifesize photos of their former, fatter selves.
"People will think they're fine," she said. "People have no clue of how big they are."
Vash also believes BMI is a valuable tool.
"The data is overwhelming to suggest that people who have elevated BMIs are at risk to develop a myriad of health care problems linked to disability, disease and death," he said. "If you know your BMI and you know what it means, then you have within your person the ability to make the necessary changes."
Times news artist Jeff Goertzen contributed to this report.
WHAT DOES BMI LOOK LIKE?
Body Mass Index has become the nation's quickest gauge of obesity. Judging by BMI, about two-thirds of Americans are overweight, with a BMI of 25 or over. About 30 percent are obese, with a BMI of 30 or over.
But what does BMI look like? The photos below show that people with similar BMIs can look very different. Michael Mawicke and Tera Guzman are competitive bodybuilders and personal trainers. Paul and Cindy Deck joined a gym together this spring.
BMI is: obese
Normal weight range using BMI: 137 - 184
BMI is: obese
Normal weight range using BMI: 137 - 184
BMI is: normal
Normal weight range using BMI: 95 - 128
BMI is: normal
Normal weight range using BMI: 101 - 136
Web sites with BMI calculators include: www.nhlbisupport.com/bmi/bmicalc.htm and www.cdc.gov/nccdphp/dnpa/bmi.
Sources: National Institutes of Health, Centers for Disease Control and PreventionDL:
Adult body mass index
To calculate your own BMI, divide your weight in pounds by the your height in inches squared. then multiply by 703.
BMI Weight status
Below 18.5 Underweight
30.0 and above Obese