You may have heard the saying: there are no fat people over 60. The idea is that by that age, fat people have either lost weight or are no longer with us.

Now, a new study has found that adults over age 60 who are in good shape -- as measured by cardiovascular fitness — live longer than those who are not, no matter how fat they might be. It may be better to be overweight and get regular exercise than to be thin and be a couch potato. Many previous studies have shown that both obesity and inactivity are associated with a higher risk of premature death in the middle-aged.

Experts have always assumed the same was true for older adults, but now, they are not so sure. According to the study, which appears in the December 5 issue of JAMA, Xuemei Sui, M.D., of the University of South Carolina and colleagues examined the connections between a person's cardiovascular fitness, body fat, and death. The group followed 2,603 older women and men for 12 years. Fitness was judged by a treadmill test and fatness was measured by body mass index (BMI), waist circumference, and body fat percentage.

"We observed that fit individuals who were obese, (such as those with BMI of 30.0-34.9, abdominal obesity, or excessive percent body fat), had a lower risk of all-cause mortality than did unfit, normal-weight, or lean individuals. Our data therefore suggest that fitness levels in older individuals influence the association of obesity to mortality," the authors say.

What does this mean for today's elderly? "It may be possible," the authors say, "to reduce all-cause death rates among older adults, including those who are obese, by promoting regular physical activity."

So what can you do to get into this healthy category? The authors recommend extended moderate exercise such as walking briskly for 30 minutes most days a week.

In other words, if you are over 60, whether you are fat or thin or in-between, the best thing you can do for a longer life is to get some substantial regular exercise.