Fitness Provides Protection Against the Health Risks of Body Fatness
Many people assume that if they are thin then they are healthy. Recent evidence suggests that the health risks of body fatness are modified by fitness level. In this study, 21,925 mesn aged 30-83 completed maximal treadmill tests and body composition assessments as part of a medical visit to the Cooper Clinic. The population was divided by composition levels into Lean (< 16.7% fat), Normal (16.7-25%) and Obese (> 25) and then subdivided by fitness level into Fit and Unfit categories based on established norms. These individuals were then followed over an average of 8 years to look at various health outcomes. Individuals in the Fit category had lower rates of death (from all causes) than individuals in the Unfit category and this relationship was consistent for all 3 body composition categories. This indicates that fatness is only a risk if a person is also unfit. It also indicates that if a person is thin, they can still be at increased risk if they are not fit.
Lee, C.D., Blair, S.N., & Jackson, A.S. (1999). Cardiorespiratory fitness, body composition, and all-cause and cardiovascular disease mortality in men. American Journal of Clinical Nutrition, 69, 373-380.