December 6th, 2011

Change in Fitness Appears More Important Than BMI Over Time

Experts have been debating the relative roles of obesity and fitness in cardiovascular risk. Now a new report from the Aerobics Center Longitudinal Study, published in Circulation, finds that maintaining or improving cardiorespiratory fitness significantly lowers CV mortality irrespective of changes in BMI.

Duck-chul Lee and colleagues followed 14,435 men for 11.4 years. Compared with people whose fitness deteriorated over time, people with stable fitness or improved fitness had significantly lower rates of all-cause and CV mortality. Here are the hazard ratios and 95% confidence intervals, after multivariate adjustment:

Stable fitness:

  • all-cause mortality: HR 0.70 (0.59–0.83)
  • CV mortality: HR 0.73 (0.54–0.98)

Fitness gain:

  • all-cause mortality: HR 0.61 (0.51–0.73)
  • CV mortality: HR 0.58 (0.42–0.80)

The authors calculated that each 1-MET (metabolic equivalents) improvement in fitness conferred a 15% reduction in all-cause mortality and a 19% reduction in CV mortality. After adjustment for other factors and change in fitness, BMI was not independently associated with either all-cause or CVD mortality.

The authors concluded that “the long-term effect of fitness change, primarily resulting from increasing physical activity, is likely to be at least as important as weight loss for reducing premature mortality.”

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