Excess weight (a body-mass index of 25 [kg/m2] or higher) and physical inactivity (less than 3.5 hours of exercise per week) together could account for 31% of all premature deaths.
"Whether higher levels of physical activity can counteract the elevated risk of death associated with adiposity is controversial," write Frank B. Hu, MD, from the Harvard School of Public Health in Boston, Massachusetts, and colleagues. "The optimal weight and levels of physical activity for longevity continue to be debated, and few epidemiologic studies have examined adiposity and physical activity simultaneously in relation to mortality."
This 24-year follow-up to the Nurses’ Health Study addressed the long-term relationship between body mass index (BMI), physical activity, and mortality in 116,564 women who, in 1976, were 30 to 55 years of age and free of known cardiovascular disease and cancer.
Of 10,282 deaths occurring during 24 years of follow-up, 2,370 were from cardiovascular disease, 5,223 from cancer, and 2,689 from other causes. In women who had never smoked, mortality increased in proportion to higher BMI (P for trend < .001). In combined analyses of all participants, adiposity predicted higher mortality independent of physical activity level.
Although higher levels of physical activity appeared to be beneficial at all levels of adiposity, they did not eliminate the higher risk of death associated with obesity. Compared with lean, active women with BMI lower than 25 kg/m2 and who performed at least 3.5 hours of exercise per week, the multivariate relative risks of death were 1.55 (95% confidence interval [CI], 1.42- 1.70) for lean and inactive women, 1.91 (95% CI, 1.60-2.30) for women who were obese (BMI of 30 kg/m2 or higher) but active, and 2.42 (95% CI, 2.14-2.73) for inactive, obese women. Independent of physical activity, even modest weight gain during adulthood was associated with higher mortality.
"Both increased adiposity and reduced physical activity are strong and independent predictors of death," the authors write. "We estimate that excess weight (defined as a body-mass index of 25 [kg/m2] or higher) and physical inactivity (less than 3.5 hours of exercise per week) together could account for 31% of all premature deaths, 59% of deaths from cardiovascular disease, and 21% of deaths from cancer among nonsmoking women…. Thus, public health campaigns should emphasize both the maintenance of a healthy weight and regular physical activity."
In an accompanying editorial, David R. Jacobs, Jr., PhD, and Mark A. Pereira, PhD, from the University of Minnesota in Minneapolis, praise this study for its "elegant analyses" and agree with the conclusion to "be fit and lean if you can be."
In conclusion: BMI and physical inactivity significantly and independently predicts mortality in women. Lowest mortality is experienced by lean and active women.
Weight gain during adulthood is a strong and independent predictor of premature death regardless of overall physical activity. Relative risk of death, cardiovascular disease, and cancer are increased by both increased weight and inactivity.
N Engl J Med. 2004;351:2694-2703, 2753-2755
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