Great news! Here's yet more evidence that should help persuade deconditioned people to get active. New research shows that if you maintain or improve your fitness level—even if your body weight does not change or increase—you are more likely to live longer.
Researchers studied 14,345 adult men, mostly white and middle or upper class. Subjects averaged 44 years old and were part of the long-term, large-scale Aerobics Center Longitudinal Study. They underwent at least two comprehensive medical exams.
The scientists used maximal treadmill tests to estimate physical fitness (maximal METs) and took height and weight measurements to calculate body mass index (BMI). They recorded changes in BMI and physical fitness over 6 years.
After more than 11 years of follow-up, the researchers determined the relative risks of dying among men who lost, maintained or gained fitness over those 6 years. Investigators accounted for other factors that could affect outcomes, including BMI change, age, family history of heart disease, beginning fitness level, changes in lifestyle factors such as smoking and physical activity, and medical conditions such as high blood pressure or diabetes.
- Maintaining or improving fitness was associated with lower death risks even after controlling for Body Mass Index (BMI) change.
- Every unit of increased fitness (measured as MET, metabolic equivalent of task) over six years was associated with a 19% lower risk of heart disease and stroke-related deaths and a 15% lower risk of death from any cause.
- Becoming less fit was linked to higher death risks, regardless of BMI changes.
- BMI change was not associated with death risks.
As you know, BMI is a measurement based on weight and height (kg/m2). MET measures the intensity of aerobic exercise—specifically, the ratio of metabolic rate during a specific physical activity to a reference rate of metabolic rate at rest.
“This is good news for people who are physically active but can’t seem to lose weight,” said Duck-chul Lee, PhD, the study’s lead researcher and physical activity epidemiologist in the Department of Exercise Science at the University of South Carolina’s Arnold School of Public Health in Columbia. “You can worry less about your weight as long as you continue to maintain or increase your fitness levels.”
Results of the study underscore the importance of physical inactivity as a risk factor for death from heart disease and stroke, said researchers. Researchers also found no association between changes in body fat percentage or body weight and death risk.
One possible explanation for these results: about 90% of the men were either normal weight or overweight at the beginning of the study. Among obese people, changes in BMI might have a significant effect on death risks. So it’s unclear whether these results would apply to severely obese people, Lee said.
Because subjects were mostly white middle- and upper-class men, it’s also difficult to know whether the findings apply to other racial and socioeconomic groups. Results for women would likely be similar, Lee said.
The study appeared in the December 6 issue of Circulation: Journal of the American Heart Association.