If the body mass index is accurate, then actor Mel Gibson, boxer Mike Tyson and California Gov. Arnold Schwarzenegger all fall into the obese category.
Other seemingly fit folks -- including San Francisco Giants outfielder Barry Bonds and Texas Rangers designated hitter Sammy Sosa -- would be considered overweight by BMI standards.
And there lies the problem with the BMI, used to calculate body fat based on height and weight. While it's a handy tool, it is often inaccurate because it does not take into account the role that muscle plays in the equation. Since muscle weighs more than fat, athletes could end up with a BMI higher than 25, which puts them in the overweight category. They may be more fit than fat, but their BMI will say otherwise.
Other tools have been used to help people get a better picture of how lean or fat they are. None is 100 percent effective -- with one exception.
"The only sure way to measure how much body fat someone has is to do it when they're dead," said Phillip Ross, an exercise specialist for Carter Rehabilitation and Fitness Center at Baylor All Saints Medical Center at Ft. Worth.
For those not willing to go to that extreme, here's a rundown on ways to measure body fat.
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Online BMI calculator
How it works: Just punch in your height and weight. Voila!
How accurate it is: Within 10 percentage points of immersion testing
Pros: Inexpensive and easy
Cons: Not as accurate for muscular types and the elderly
Where to find it: bmi-calculator.net; nhlbisupport.com/bmi; caloriecontrol.org
How it works: A tape measure is used around the waist and hips
How accurate it is: Not very
Pros: It is an important predictor of disease. A recent study by UT Southwestern Medical Center researchers found that people with a larger waist-to-hip ratio may be at increased risk for heart disease.
Cons: Does not tell how much fat a person has, just where she stores it. So someone who is overweight may have hips that are a lot larger than her waist. The ratio is good, but she's still overweight.
Where to find it: bmi-calculator.net/waist-to-hip-ratio-calculator
How it works: Calipers measure folds of skin and fat
How accurate it is: Not precise but better than two previous methods. Margin of error is plus or minus 3 percentage points.
Pros: Inexpensive and easy
Cons: It's not practical to do this test on someone who is 5-foot-2 and weighs 230 pounds because she has more inches of skin than the calipers can get around. It's hard to find the right places to pinch every time. It's best to have the same person do repeated tests.
Where to find it: Many fitness centers offer it.
Bioelectrical impedance test
How it works: Person holds device in both hands and a sensor sends a harmless radio-frequency pulse throughout the body. It measures fluid content.
How accurate it is: Margin of error is plus or minus 4 percentage points. If person is dehydrated, the reading may be altered.
Pros: Easy to do
Cons: Water consumption can alter reading.
Where to find it: Health clubs, sports medical centers
Hydrostatic weighing (the dunk test)
How it works: Ideally people should be completely nude before the test begins. After they expel all of the air from their lungs, they are repeatedly submerged in water for five to 10 seconds.
How accurate it is: Very. Margin of error is plus or minus 1 percentage point.
Pros: It's the gold standard. Considered the most accurate assessment of body composition.
Cons: It can be scary for someone who has a fear of being under water. Did we mention you should be nude? It's not widely available. Cost is $80.
Where to find it: Ultimate Test Lab is setting up testing locations in the Chicago area. Go to ultimatetestlab.com for more information.
How it works: Person sits in what looks like a giant egg for 20 seconds. It then measures air displacement.
How accurate it is: Margin of error is plus or minus 3 percentage points.
Pros: It's suitable for athletes, the elderly and children.
Cons: It's not readily available.
Where to find it: East Bank Club, 500 N. Kingsbury St. (for members only)
[SOURCES: AN EPIDEMIC OF OBESITY MYTHS, NATIONAL INSTITUTES OF HEALTH, COOPER AEROBICS CENTER]