Fitness linked to reduced mortality, even in obese subjects

Shelley Wood

December 04, 2007

Columbia, SC - Another study exploring the relationship between being fat, being fit, and living longer has found that lower fitness is an independent predictor of all-cause mortality, even after adjustment for adiposity[1]. In the study, obese subjects who were fit had a lower risk of dying than normal-weight subjects who were physically inactive.

"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 . . . which will keep most individuals out of the low-fitness category," the authors, led by Dr Xuemei Sui (University of South Carolina, Columbia), write in the December 5, 2007 issue of the Journal of the American Medical Association.

The study tracked a cohort of 2603 adults aged 60 or over for a mean of 12 years, during which time 450 people died. Adjusted death rates were lowest for people with the lowest body-mass index (BMI), lowest waist circumference, or in the highest quintile for fitness level—this last that held true even in severely obese subjects, who were much less likely to die if their fitness levels were higher. When waist circumference was factored into the fitness analysis, fitness continued to predict mortality risk regardless of smoking, baseline health, BMI, waist circumference, or body-fat percentage, whereas, by contrast, waist circumference was no longer significantly associated with increased mortality after fitness was considered.

"Normal-weight individuals in our study had greater longevity only if they were physically fit; furthermore, obese individuals who were fit did not have increased mortality," the authors conclude.

Focusing on physical activity, not fat

In an interview with heart wire , senior author on the study, Dr Steven N Blair (University of South Carolina), suggested that the findings speak to the value of prescribing fitness, rather than focusing solely on weight loss in older subjects.

"This does not say that we should ignore obesity in this older population or any other, but it does underscore the extreme importance of being active and fit, whether you're normal weight, overweight, or obese," he said. Indeed, in his study, only half of subjects with class II obesity were in the lowest category of physical fitness.

"We've put so much emphasis on weight loss, and obesity is awful—it's the biggest health problem we've ever had, etc," Blair pointed out. "But that strategy doesn't seem to be particularly effective; we've been doing it for a couple of decades." Instead, Blair says he now focuses on reminding his patients to walk for at least 30 minutes five days a week, eat a healthy diet, and try not to gain additional weight. "And I think that's good advice. A lot of people say, well, I did what the doctor told me and I started taking those three 10-minute walks a day and I only lost a pound over six months, and I said, to heck with it. But I tell them, exercise is good for you regardless of whether you lost a lot of weight or not."

Blair also acknowledged that while the analysis showed no mortality costs of obesity in fit subjects, there are other social and medical reasons for losing weight.

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