Physical fitness and obesity are associated in a dose-dependent manner in children

To analyze the relationships between physical fitness, lifestyle-related factors, and obesity in a large population of children.

A cross-sectional study design including children aged 7-12 years (n = 715) was used. Adiposity measures included subcutaneous fat mass (SFM) and body mass index (BMI). Physical fitness and lifestyle-related factors were also assessed.

When SFM was used as the adiposity variable, the odds ratios (OR) for being obese in boys in the highest quartiles of fitness were 0.02 (95% CI 0.02-0.13) for aerobic fitness, 0.04 (95% CI 0.01-0.16) for dynamic force, and 5.32 (95% CI 1.82-15.58) for running speed (in which quartile 1 corresponds to the best performance) compared with boys in the lowest quartile. In girls, the OR for those in the highest quartiles of fitness were 0.04 (95% CI 0.01-0.14), 0.16 (95% CI 0.05-0.51), and 5.24 (95% CI 1.74-15.75), respectively, showing a significant dose-response relationship between fitness and fatness in both sexes (p for trend <0.001).

An inverse relationship between physical fitness levels and the risk of being overweight/obese was found inasmuch as children with higher physical fitness seem to be more protected against fat mass accumulation than their counterparts with lower fitness levels.