Issue 131 Item 7 Physical Fitness Does Not Alleviate Detrimental Effects of Obes

Investigators report, that cardiorespiratory fitness can not substitute for leanness in protecting one’s health nor can being slender totally alleviate the effects of being unfit. Dr. June Stevens and associates at the University of North Carolina in Chapel Hill evaluated data from the Lipid Research Clinics Study in which subjects were examined between 1972 and 1976, and data regarding vital status were collected through 1998. Included were 2506 women and 2860 men whose mean ages were 46.6 years and 45.1 years, respectively, at baseline.

Fitness level was estimated using the time to reach a predicted maximal heart rate, based on age and training, during a standardized treadmill test. Seven percent of the women and 10% of the men who were the most fit were also obese, they report in the November 1st issue of the American Journal of Epidemiology.

The authors evaluated mortality rates, fitness levels and body mass index (BMI). Hazard ratios were estimated with subjects classified as "fit-not fat (the reference), fit-fat, unfit-fat, and unfit-not fat," adjusting for age, education, smoking, alcohol intake, and Keys score for dietary intake.

For men whose level of fitness and BMI were both in the top quintile, the risk of all-cause mortality was 1.25 compared with men who were fit and not obese. The corresponding hazard ratio was 1.32 for women. For cardiovascular disease (CVD) mortality, the adjusted hazards ratios were 1.39 for both sexes, although the authors note that the difference between women in this group and the reference group did not achieve statistical significance (p > 0.1).

For women who were not obese but unfit, the hazard ratios for all cause and CVD mortality were 1.30 and 1.53, respectively. The corresponding ratios for men were 1.44 and 1.55.

All cause and CVD mortality ratios for obese, unfit women were 1.57 and 1.95, respectively. The corresponding ratios for men were 1.49 and 1.67.

"To best reduce the risk of mortality, fit persons need to attain or maintain a normal body weight, and normal weight persons need to attain or maintain at least a moderate level of fitness," Dr. Stevens’ group concludes. Am J Epidemiol 2002;156:832-841.