by Patrick Appel

A reader writes:

Don't put too much credence in the body-mass index (BMI), it does not take into account body composition.  It's basically weight divided by height.  You can be 6'2" and weight 225 pounds with three percent body fat or with twenty percent body fat and score the same.  One of the reasons we, as Americans, have put on more weight in recent years is because our exercise habits have changed.  We lift weights more (look at the difference in college and pro athletes today vs thirty years ago), which builds more muscle which weighs more than fat (by about a 2:1 ratio).  My guess is Americans simply work out more today than they did in the past, and one of the byproducts is that they end up weighing more because they have more muscle mass than previous generations.

The BMI is a crude tool that is taken way too seriously.  There is a trainer at my gym, a former professional body builder, who today probably has less than 6% body fat that was recently told by an insurer that he was obese and uncoverable because his BMI was too high.  I don't know anyone in better shape than this guy but he was considered obese because of muscle mass.  The focus needs to be on body composition, percentage of body fat, muscle mass, and the like.  I'm 6'1" and weigh 255 pounds, which under the BMI would make me obese.  But most of that weight is muscle, in fact, most people are shocked when I tell them how much I weigh.  I've been weight lifting since I was 15, and I'm now 31.  There is no way I could possibly get down to the 204 pounds necessary to be considered "normal" weight (which coincidently was my weight when I graduated from high school) without losing a signifiant amount of muscle mass (which, for a variety of reasons, may be unhealthy).

This is not to say there are those among us to are overweight in the sense that most people think about it.  But there is a very real disconnect between the "statistics" and perception.  I'm guessing most people wouldn't consider me out of shape, but according to the BMI, I'm a fat slob.

BMI can be misleading, but I believe it's relatively uncontested that America, as a whole, has gotten chubbier over the past several decades. If you want a contrast to the New Yorker article, Radley Balko has defended the fattening of America in the past.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.