The research reinforces a counterintuitive point that past studies have suggested -- being a bit on the heavy side may actually cut your risk of dying prematurely.
In the review, published in this week's Journal of the American Medical Association, researchers looked at nearly 100 studies involving 2.88 million people that compared body mass index, or BMI, to the risk of death from any cause.
BMI is derived from a formula that compares your height to your weight. It is currently the standard means of determining whether someone is underweight, of normal weight, overweight or obese.
Not surprisingly, the researchers found that the heaviest among us -- those who have a BMI above 30 -- have a higher risk of death than those who are considered to be at a "normal" weight, or a BMI between 18.5 and 25.
But the researchers also found a slight dip in death risk -- about 6 percent -- in those whose BMIs were between 25 and 30. In other words, people who would be classified as overweight appear to have a lower risk of death from any cause.
Moreover, for those who were considered to be on the lower end of the obesity spectrum, with a BMI of 30 to 35, the risk of death from any cause was not significantly different from that experienced by those who were at a normal weight.
As is apparent from the number of studies examined in this review, this is not the first time that a link has been suggested between being a tad on the heavy side and having a decreased risk of death. And several past studies have disputed this link. But this new review may lend support to the idea that our health may not be as closely tied to the numbers on our scales as we might have been led to believe.
Lead study researcher Katherine Flegal, Ph.D., of the CDC's National Center for Health Statistics, said the review was in many ways a follow-up to research she and her colleagues published in 2005 that suggested a slightly higher-than-normal BMI was necessarily attached to life-threatening conditions such as heart disease.
"We found that being overweight in that study was not associated with excess mortality from cardiovascular disease or cancer, but it reduced mortality from other things," Flegal said. "There's even some research that suggests body fat itself could be cardioprotective."
On one hand, said obesity experts not involved with the research, the findings suggest that the current widespread use of BMI as a way to determine if one is overweight or obese may need to be reconsidered. Flegal said that the problem may not be the BMI scale, but, rather, how the different rungs on the BMI ladder are interpreted by doctors. In this way, such research may have implications for physicians who currently advise patients in the overweight BMI category to lose a few pounds.
"These are not health categories, these are weight categories," Flegal said.
Dr. David Katz, director of Yale University's Prevention Research Center, agreed that this review supports the idea that doctors may need to reexamine the way they advise certain patients.