Big, Fat Mistake About Your Body

President Bush and I have several things in common. We run dozens of miles per week; we have similar 5K race times; we are in excellent overall health; we are perceived as trim by most nonanorexic observers; and we are both dangerously overweight, according to the U.S. public health establishment.

The president and I are weighed down by body mass index figures above 25. This is endangering our health, according to public health authorities, who claim that, in the words of Walter Willett and Meir Stampfer of Harvard Medical School, a BMI above 25 is “a major contributor to morbidity and mortality.”

In fact, there is no sound, scientific basis for concluding that all people whose BMI exceeds the standard are overweight. The claim, like many about weight, turns out to be based on faulty science, eating-disordered thinking and the projection of anxieties about social overconsumption onto the issue of body mass.

Body mass has an unclear relationship with health, and the waters get even muddier when researchers take into account such factors as activity levels, weight cycling brought on by dieting, poverty, social discrimination and many other variables that disproportionately affect the two-thirds of American adults who are said to be too fat.

It’s time to change the message: Focusing on weight loss as the goal is counterproductive. A great deal of evidence suggests that losing weight and gaining it again -- the outcome of perhaps 95% of all diets -- is medically dangerous. In other words, the nation’s $50-billion-a-year weight loss industry is a major contributor to many of the health problems it ascribes to the imaginary “disease” it has failed so spectacularly to cure. (Dieters actually end up weighing more, on average, than people of similar initial weight who never diet.)

But there is something that works to improve health. Numerous medical studies have found that activity levels are far better predictors of health than weight, and that sedentary people of all sizes derive terrific health benefits from becoming active, even though such changes often produce little or no weight loss.

Public health officials justify their increasingly aggressive efforts to slim Americans down by claiming that simply being “overweight” causes heart disease, hypertension, diabetes and some forms of cancer. But it’s hard to avoid the conclusion that our public health establishment’s obsession with making people thinner is irrational.

The relationship between disease and weight is quite complex. A study that finds, say, a correlation between weight loss and decreased risk for some disease is often unable to determine whether the decrease in risk is the result of weight loss per se or of the lifestyle changes that accompanied the weight loss. Studies have suggested that the risk association between higher body mass and some heart disease may be a product of the tendency of those with higher body mass to lose and then regain weight. And large-scale studies demonstrate that most of the excess risk for diabetes in adults can be eliminated by lifestyle changes, whether or not these changes make people substantially slimmer.

What of the claim, made by the U.S. surgeon general in 2001 and repeated thousands of times in the media since then, that obesity is killing hundreds of thousands of Americans annually and that excess weight soon will surpass smoking as the nation’s leading cause of preventable death? Again, it’s more complicated. It ignores many other variables often associated with obesity that are more likely the true culprits in causing preventable deaths, including sedentary lifestyles, roller coaster diets and poverty.

Still, hysteria about weight has reached such a pitch that something like Morgan Spurlock’s preposterous film “Super Size Me” has elicited rave reviews from normally levelheaded observers. (Spurlock gained weight by eating the caloric equivalent of 18 hamburgers per day for a month while remaining completely sedentary. Doing this to prove hamburgers are deadly makes as much sense as drinking a case of beer every day for a month to demonstrate we ought to bring back Prohibition.)

The advice our public health officials ought to be giving Americans is to imitate Bush: that is, to find some form of physical activity they enjoy and engage in it regularly, while paying no attention to the scientifically spurious idea that someone with a BMI above 25 should try to lose weight. Claiming everyone must have a BMI under 25 to be healthy is every bit as absurd as claiming everyone must be more than 6 feet tall to be healthy -- and it’s about as achievable a goal.