Fitness, Not Fat, Predicts Longevity

Men and women who were considered fit, as judged by a treadmill test, but were overweight or obese had a lower mortality risk than those of normal weight but with low fitness levels.

The study, conducted by Xuemei Sui, M.D., of the University of South Carolina, Columbia, and colleagues examined the associations between cardiorespiratory fitness, various clinical measures of adiposity (body fat) and death in 2,603 older women and men, age 60 years or older (average age, 64.4 years; 19.8 percent women). Subjects were enrolled in the Aerobics Center Longitudinal Study and completed a baseline health examination during 1979-2001. Fitness was assessed by a treadmill exercise test and body fat was assessed by measuring body mass index (BMI), waist circumference, and percentage of body fat. Low fitness was defined as the lowest fifth of the sex-specific distribution of treadmill exercise test duration. 450 deaths occurred over an average follow-up of 12 years.

Those who died were older, had lower fitness levels, and had more cardiovascular risk factors than survivors. However, there were no significant differences in the measure of body fat. Participants in the higher fitness groups were for the most part less likely to have risk factors for cardiovascular disease, such as hypertension, diabetes, or high cholesterol levels, and fit subjects had lower death rates than unfit subjects within each level of body fat, except for two of the obesity groups. In most instances, death rates for those with higher fitness were less than half of rates for those who were unfit.

The study showed that even a modest effort to improve physical activity can provide health benefits, the researchers said. Those in the bottom fifth in terms of fitness were about twice as likely to die than those in the next fifth.

"You shouldn't be scared and think, 'Oh, I'm overweight, I'm obese, it's useless for me to be physically active,'" said Dr. Sui. The researchers encouraged people to get even moderate physical activity, which, while it may not reduce a person's weight, would keep them at a level of fitness that could prolong their life.

Researchers concluded by saying, "Our data provide further evidence regarding the complex long-term relationship among fitness, body size, and survival. It may be possible to reduce all-cause death rates among older adults, including those who are obese, by promoting regular physical activity, such as brisk walking for 30 minutes or more on most days of the week (about 8 kcal/kg per week), which will keep most individuals out of the low-fitness category. Enhancing functional capacity also should allow older adults to achieve a healthy lifestyle and to enjoy longer life in better health."

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