Wednesday, 20 April, 2005

Slightly overweight? No problem.

Remember when I saidthat the Body Mass Index standard was skewed toward an unrealistically thin goal, and that the "fat epidemic" that people have been screaming about is perhaps a bit overblown? According to an Associated Press article today, a recently published analysis of mortality and BMI published in today's Journal of the American Medical Association shows that people who are slightly overweight actually have a lower incidence of early death than those of "normal" weight. Obesity, defined as having a BMI value of 30 or higher, is indisputably lethal, but slightly overweight is not the major health risk that it's been made out to be. This information comes as no surprise to many, as other studies have found the same thing.

A CDC study last year listed overweight and inactivity as the second leading cause of preventable death, attributing 400,000 deaths per year. The study warned that soon obesity would overtake tobacco as the leading cause. The new study attributes only about 112,000 deaths to excess weight, and then subtracts the benefits of being modestly overweight to arrive at a figure of about 26,000. That places weight-related deaths in seventh place, behind car crashes.

It sounds like some suspicious number crunching to me, but it's pretty obvious that neither the CDC nor anybody else in the medical research community has any idea what the real numbers are. My gut feeling is that the numbers are closer to 112,000 than 400,000, but that's a pretty wide range. The CDC isn't going to abandon its campaign on fat, which is probably a good thing, but I'll bet they revisit their BMI calculation sometime in the next few years.

Nobody knows yet why slightly overweight (according to BMI) people are healthier than people of "normal" weight. I think it's because "normal" BMI is unhealthily thin, but I don't have any hard data to base that on. A related study, also in today's JAMA, finds that overweight Americans are healthier than ever due to better maintenance of blood pressure and cholesterol. I suspect that's true.

Obesity is still a problem, but the "fat epidemic" is almost surely less of a problem than the CDC and other organizations have made it out to be. Beware of government hype. It'll get you every time.