Most people know that it's unhealthy to be overweight or, especially, obese. But what if you are physically fit? Could fitness cancel out the health risks associated with being overweight? Some studies suggest this, including a recent one in Circulation.

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The study looked at 14,345 middle-aged men; 47 percent were overweight, another 10 percent obese. Those who maintained their cardiorespiratory (aerobic) fitness levels during a six-year period were 30 percent less likely to die over the next decade, notably from heart disease or stroke, than those who became less fit. Those who became fitter, were 40 percent less likely to die. This was true regardless of their weight status.

Simply put, overweight or obese men who became fitter, on average, fared as well as or better than lean men who became less fit. So fitness may be more important that weight when it comes to life expectancy. Some previous research found this is less true for women, however, and it may not apply to very obese people, who were underrepresented in this study.

Still, this is good news for overweight people who are unable to lose weight or keep it off. If they exercise and stay fit or become fitter, they're likely to benefit even if they don't lose weight. "The long-term effect of...increasing physical activity is likely to be at least as important as weight loss for reducing premature mortality," the researchers concluded.

Thus, the health risks of being obese may be lessened or even eliminated if you exercise and stay fit. Of course, being overweight and being unfit often go hand in hand—lack of physical activity contributes to obesity. And conversely, obesity keeps many people from exercising and thus can, in turn, reduce fitness. When obese people start exercising and become fit, they tend to lose weight, particularly when they control their calorie intake (that's why there are relatively few very fit obese people in such studies).

While experts continue to debate about the relative effects of fitness and body weight on health and mortality, most research shows that there are health benefits to both maintaining a healthy weight and being fit. It isn't either/or.

Adapted from The University of California, Berkeley Wellness Letter (March 2012)

Publication Review By: the Editorial Staff at

Published: 15 Feb 2012

Last Modified: 03 Feb 2015