Weight, not aging, may cause fatigue.

• Position: Fitness - During exercising - Brief Article

If activities leave you more tired than in the past, don't be too quick to blame your age. Weight gain and a lack of regular exercise might turn out to be

the real culprits. "People often blame their age for slowing down in activities such as playing catch with the kids or grandchildren, or that walk in the woods or that bike ride across town. But a weight gain of 15 or 20 pounds in any adult can cause more fatigue during exercise, an increase in postexercise joint or muscle pain, and may generally limit the amount of activity that feels comfortable," explains William Haskell, deputy director of the Stanford (Calif.) Center for Research in Disease Prevention.

The good news is that "the loss of excess weight through a combination of calorie restriction and regular exercise can turn the clock back so that you can exercise at a level that was comfortable 10 or even 20 years ago," he says, noting that the effects of aging itself on lung and heart capacity are minimal. "While the maximum heart rate decreases about one beat per year because of aging, this has only a small effect on a person's exercise capacity in his or her 60s, 70s, or 80s." Fit, generally healthy individuals can live well into their 80s or 90s before age-related decreases in lung and heart function become an issue.

Weight slows people down and "puts more stress on joints, which can make underlying conditions such as...