Keep the weight, live longer?
A new study published in the Journal of the American Medical Association found that overweight people are the least likely to die from any cause -- even when compared to those who are of normal weight.
Adults with a body mass index that qualifies them as overweight but not obese -- between 25 and 29.9 -- were the least likely to die of any group, with a 6 percent reduced risk of all-cause death, compared to normal-weight individuals with BMIs of between 18.5 to 24.9. About 30 percent of the U.S. adult population has a BMI of 25 to 29.9, reported the Wall Street Journal.
Overall, any level of obesity was associated with an 18 percent increased risk of death. But those who were on the lower-end of obesity -- scoring 30 to 35 on the BMI scale -- had a five percent reduced risk of dying, though this was considered statistically insignificant. And those with a BMI of at leasperct 35 were 29 percent more likely to die for any reason, found the study's researchers, from the U.S. Centers for Disease Control and Prevention.
In a comprehensive meta-analysis of 97 studies, investigating 2.88 million study participants around the world, the CDC researchers conducted a more definitive investigation of the link between body weight and overall mortality. This surprising finding is not the first of its kind -- the phenomenon of longevity among those with extra weight is often called "the obesity paradox" because of the myriad chronic conditions that a high BMI does cause, such as Type 2 diabetes, hypertension, heart disease and some cancers.
So how could having extra weight, which increases the risk of illness, not also increase risk of death?
"Even in the absence of chronic disease, small excess amounts of adipose tissue may provide needed energy reserves during acute catabolic illnesses, have beneficial mechanical effects with some types of traumatic injuries, and convey other salutary effects that need to be investigated in light of the studies by Flegal et al and others," wrote Steven B. Heymsfield, M.D., and William T. Cefalu, M.D., of the Pennington Biomedical Research Center in an accompanying editorial. In other words, a few extra pounds could help assuage disease-associated wasting or provide some additional "cushioning" in the event of a traumatic injury.
"Not all patients classified as being overweight or having grade 1 obesity, particularly those with chronic diseases, can be assumed to require weight loss treatment," they added.
Still, obesity researchers caution not to take the advice too much to heart. This is hardly an excuse to pack on extra weight or slag off on those New Year's resolutions. For one thing, BMI is an imperfect measure of body fat and overall health. The diagnostic tool uses a weight-to-height ratio that doesn't factor in, say, muscle mass versus fat mass. That means an athletic person could fall into an "overweight" category despite having a relatively low body fat percentage, and markers of longevity such as a high aerobic capacity and a healthful diet.
The BMI measure also doesn't factor in the location of fat, which can affect the relationship to disease and mortality. For example, recent research has found that belly fat is associated with early death and a host of chronic conditions.
What's more, the findings are in all-cause mortality rather than illness and lifestyle. A modest ten pounds can have an impact on cholesterol levels, blood pressure, diabetes and other diseases that can contribute to a lower lifespan, but also contribute to diminished mobility, independence and overall wellness.