Harvard Heart Letter

Ask the doctor: The trouble with the body mass index

Q. So many times I have read that people with a BMI greater than 25 are overweight. I'm a man 5 feet, 5 inches tall weighing 168 pounds. My BMI is 28. I have a flat stomach. I lift weights and do push-ups and pull-ups. Does the BMI mislead body builders and athletes by saying we are overweight?

A. You are correct that body mass index (BMI) is a very imperfect measure of obesity. It does not account for differences in body shape and muscularity, and if you are very muscular, then your BMI of 27.95 is not worrisome at all.

The reason BMI gets so much attention is that it is easy to standardize, and measuring it does not require special equipment. If we had an easy way to measure belly fat, for example, that would likely get much more attention than BMI. But we don't.

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