Hefty is healthy?!
In April 2005, a study published in the Journal of the American Medical Association (JAMA) reported that obesity increased the risk of premature death much less than previously estimated. Even more surprising, the authors, who are researchers at the Centers for Disease Control and Prevention (CDC), concluded that being overweight (but not obese) was not associated with early mortality. Everyone carrying around a little extra weight cheered as headlines declared, "Some Extra Heft May Be Helpful." So, no doubt, did many in the food industry.
But you know what they say about anything that sounds too good to be true. Other researchers (including several at Harvard) believe the unexpected findings came from methodological errors in the study. These critics say the CDC researchers didn't take into account two important variables: smoking and illness.
Thin people smoke more than heavier people (in one study, 40% of those with a BMI under 21 versus 25% of those with a BMI of 29 or higher). Indeed, smokers may be thinner because they smoke. If you don't factor that in, a study may find that thinner people die earlier because they're thin. In reality, it's because they smoke.