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.
"In a society prone to both epidemic and increasingly severe obesity, it may be that those who manage to remain in the 'overweight' class are, in fact, those who are actually doing quite well," said Katz, who was not involved with the study. "This study suggests that if the basis for defining 'overweight' is adverse health effects, we may want to raise the threshold. The definition of 'overweight' should begin where health risks begin."
Katz pointed out that the study looked only at death rates -- not quality of life. And this is an area, he said, that may be affected by being overweight or slightly obese.
"We have recent evidence -- from the Lancet's 'Global Burden of Disease' study -- that we are living longer, but sicker," he said. "It may be that overweight does, indeed, contribute to type 2 diabetes and heart disease, but not to premature death.
"Living is not really the prize; living well is the prize. So we should be careful before jumping to conclusions about these findings."
Dr. Mitchell Roslin, chief of obesity surgery at Lenox Hill Hospital in New York, said it is important to recognize that many people who are overweight may in fact be moving toward obesity and its myriad health effects.
"Your weight is a moving target, and usually in the wrong direction," Roslin, who was also not involved with the study, said. "Unfortunately, many people gain several pounds each year and this becomes a pathway to morbid obesity, which, as the study shows, is very detrimental."
Katz agreed. "'Overweight' does not tend to be a permanent state; it is often a transitional state, leading to obesity," he said. "If you are lean and gain weight, you will become overweight. If you continue to gain weight, you will become obese. If you are slightly overweight, and remain that way, it means you are actually controlling your weight better than most -- and perhaps that's why health risks may not ensue.
"This study is an argument for, not against, weight control -- it just may be an argument for controlling weight in a slightly wider range than we thought."
So this New Year's, as you find yourself standing on the scale, what should your resolution be? Flegal, for one, said that this study should not be a guide to individual action. But Roslin said the study may provide some perspective for those worried about how their weight might be affecting their health.
"The most important message is to eat right and be fit," he said. "Nominal weight loss and stabilization are worthwhile goals. Skinny is not always better."