The Obesity Paradox: Weigh More and Live Longer

The health blogosphere is awash with the new study that says overweight people may indeed live longer.

The counterintuitive findings that people who are overweight live longer, published today in the Journal of the American Medical Association, couldn’t have been more perfectly timed, coming as it has right when people are resolving to be healthier — which involves, for many, losing weight.

In many places where this story has been picked up, including The New York Times, The Wall Street Journal, and Time, the implication seems to be that the push to get people down to a “healthy” weight has been overblown.

But that being overweight is associated with increased lifespan isn’t new. It’s called the “obesity paradox,” and studies documenting it have lead to widespread speculation about the potential “protective benefits” of excess body fat.

For some health advocates, the implication is downright offensive. Walter Willett of the Harvard School of Public Health, for example, lost his cool this morning on NPR, declaring, “This study is really a pile of rubbish and no one should waste their time reading it.”

But the study’s author, Katherine Flegal of the Centers for Disease Control and Prevention, mounted a solid defense: “It’s statistically significant.” Those three words carry weight — if an association has been found to be significant, it tells us that if nothing else, we need to acknowledge that the results are in some way legitimate and warrant our attention.

The findings are without doubt interesting, which on its own makes the study worth reading. The problem is that despite the grandness of the meta-analysis — it takes into account over 3 million people! — it still has an extremely limited scope. It looks at BMI, and only BMI, in relation to death, regardless of cause. It’s impossible to report on its baseline conclusion without taking into account substantial caveats.

Just remember your weight is only one metric to your overall health.

It is very important, and do not think you can slack because of this study. But, do keep the context in mind.