Is Obesity Really Unhealthy?

In The Obesity Myth: Why America's Obsession with Weight is Hazardous to Your Health (Gotham, 2004), Paul Campos does a good job of proving that BMI is a poor measure of either health or health risk. What he doesn't do a good job of proving is that excess fat is not linked to health problems, that Americans are not getting fatter on average, and that this is not a problem.

Campos makes the point that focusing on weight - on a mere number - can and does result in unhealthy yo-yo dieting. More importantly, however, he exposes how the obsession with weight is a war of moral judgment as much as it is a war against poor health. As a result, what was once considered a vice - physical vanity - has become one of our highest cultural values.

The problem with BMI as a measure of health, of course, is that it does not begin to account for body composition (fat verses muscle), activity level, or diet. It's just a number that reflects a formula of height and weight, and nothing more. People can fall in the obese range of the BMI charts without having a poor diet and lacking exercise; many athletes fall in that range. So perhaps BMI should be abandoned as a measure of health. However, that doesn't mean that, all other things being equal, a person carrying around 20% body fat isn't in better shape than a person carrying around 35% body fat.

Not only does BMI fail to account for diet and exercise, but its current ranges seem highly unrealistic: 70% of Americans fall in either the overweight or obese category, and, when it comes to lifespan, those with an "overweight" BMI live longer, on average, than those with an "ideal" BMI. It may not be, as Campos claims, a myth that excess fat is linked to health risks; it may simply be a myth that BMI is a good measure of excess fat. Those of us who are obese or overweight need not strive to reach our "ideal BMI." We should, however, just like underweight and "ideal" people, strive to limit our consumption of junk food, increase our consumption of healthy foods, and exercise regularly.

Obesity doesn't cause poor health. Poor diet and lack of exercise cause poor health. It just so happens that, a lot of the time, poor diet and lack of exercise also cause obesity. Campos is correct that correlation doesn't necessarily imply causation, but correlation does imply correlation. Maybe the morbidly obese person, as Campos argues, won't become healthier just because she loses weight, but she'd certainly be healthier if she had never become morbidly obese in the first place. Campos is probably right that weight is very hard to lose (and almost impossible to keep off long-term), but that may be precisely the reason to encourage healthy eating and exercise habits beginning in childhood.

While there is much truth in this book, it unfortunately could encourage an obese person to just pop open another can of cheese balls and skip a few more exercise routines, because, hey, weight isn't really linked to health. Maybe not, but the things that make you fat in the first place are. And while, on average, overweight people live longer than skinny and "ideally" weighted people, obese people do not. So don't worry about where you fall on the BMI chart. Rather, eat healthy foods, limit unhealthy foods, and exercise regularly.