BMI, or body mass index, is a formula used to figure out people's percentage of body fat. Controversy exists around the use of BMI as an accurate measuring tool but this method persists because of the ease and convenience of its calculations. In a medical office it would take extra time to calculate fat percentage using other means, so the BMI formula remains the standard in the medical profession.
BMI Ranges
BMI is a formula based on height and weight meant to predict obesity and possible health risks in the general population. The BMI is supposed to be a correlation to percent body fat, with a higher BMI meaning a higher percentage of body fat. A normal BMI ranges from 18.5 to 24.9. A BMI ranging from 25 to 29.9 means overweight, and anything higher than 30 means obese. Numbers higher than 40 mean morbid obesity.
Errors
Muscle is more dense than fat, so someone who is well-muscled will have a higher body weight leading to a higher overall BMI. Athletes who are well-muscled may appear obese if BMI is the only measurement considered. A study published in "Medicine and Science in Sports and Exercise" in May 2007 compared the BMI of athletes and non-athletes. The study found that the BMI of athletes commonly put them in the overweight range even though the athletes were not actually overweight. The study concluded that alternative methods should be used to measure fat percentage in college-age athletes.
Other Measurements
More accurate measurements for athletes would be a caliper or pinch test in which several areas on the body are measured to calculate body fat percentage. The American Counsel on Exercise indicates the pinch test in males is done in three areas; on the chest between under the arm and the nipple, midway on the front of the thigh, and on the abdomen near the belly button. For women the measurements are taken from the back of the arm, midway on the front of the thigh, and just along the front of the hip bones near the abdomen. Other tests used to measure body fat include hydrodensitromitry or dunk tank, bioelectrical impedance, dual-energy x-ray absorptiometry and computerized tomography.
Considerations
If BMI is one of the few available measures for an athlete, keep in mind that a BMI in the overweight category is more likely. Using waist circumference and waist-to-hip ratio will help solidify this argument. Having a low abdominal circumference with a higher BMI may indicate the athlete has more muscle than fat and is in a safe weight range. Body fat percentages should be 14 to 24 percent for fit or average men and 6 to 13 percent for athletic men; for fit or average women look for 21 to 31 percent, with 14 to 20 percent for athletic women, according to the American Counsel on Exercise.
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