In a study of more than 14,000 people, maintaining or improving fitness was associated with a lower death risk even after controlling for Body Mass Index (BMI) change, according to the American Heart Association.
Researchers used maximal treadmill tests to estimate physical fitness (maximal metabolic equivalent of task [METs]), and used height and weight measurements to calculate BMI. They recorded changes in BMI and physical fitness over 6 years. After more than 11 years of follow-up, researchers determined the relative risks of dying among men who lost, maintained, or gained fitness over 6 years. They accounted for other factors that can affect outcomes, including BMI change, age, family history of heart disease, beginning fitness level, changes in lifestyle factors, and medical conditions.
The authors found:
One possible explanation for these results, says AHA, is that about 90% of the men were either normal weight or overweight at the beginning of the study. Among people who are obese, changes in BMI might have a significant effect on death risks. It's unclear whether these results would apply to people who are severely obese.
Because the study was mostly done in white middle- and upper-class men, it's difficult to know whether the results apply to other racial and socioeconomic groups. Women would likely have similar results as the men in the study, said lead author Duck-chul Lee, PhD.
The study is published in Circulation: Journal of the American Heart Association.