Saturday, August 22, 2009

Opposite Sex but Same BMI

Situation: My sister and I went in for physicals after our father died from a massive heart attack. The doctor told us that our BMIs were 28, which meant we were overweight. He encouraged us to lose weight because it would help us reduce our risk of heart disease and some other diseases, like diabetes. I am confused about the advice we were given.
I weigh 45 pounds more than my sister and look like an average guy. My sister definitely looks overweight. How can the doctor tell us that with respect to our weight, we’re the same and both of us need to lose weight? Strategies: The BMI calculation gets at the volume, or the amount of space a person takes up, and that, in turn, is linked to how much of that space is fat. The calculation uses both height and weight. So while you are taller and heavier than your sister, your BMIs can be the same. Because men typically weigh more than women and have less body fat, it seems intuitive that the BMI cutoffs should be different, and in fact most people would say that a woman with a BMI of 25 would look better if she lost a few pounds, while a man with a BMI of 25 looks thin.
The cutoffs used to link BMI and health risk do not take appearance into account, however. When scientists have looked at BMI and health risk in men and then at BMI and health risk in women, the similarities are striking. So from a health perspective, it doesn’t make sense to have different cutoffs. Your doctor is right. Your weight is putting you (and your sister) at an increased risk for heart disease. You’d be wise to take his advice and lose some weight. With your shared family history and shared desire to improve your heart health, perhaps you and your sister should work as a team at reaching a healthy body weight.

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