Physically active lifestyle does not decrease the risk of fattening

Abstract

Background: Increasing age is associated with declining physical activity and a gain in fat mass. The objective was to observe the consequence of the age-associated reduction in physical activity for the maintenance of energy balance as reflected in the fat store of the body.

Methodology/principal findings: Young adults were observed over an average time interval of more than 10 years. Physical activity was measured over two-week periods with doubly labeled water and doubly labeled water validated triaxial accelerometers, and body fat gain was measured with isotope dilution. There was a significant association between the change in physical activity and the change in body fat, where a high initial activity level was predictive for a higher fat gain.

Conclusion/significance: The change from a physically active to a more sedentary routine does not induce an equivalent reduction of energy intake and requires cognitive restriction to maintain energy balance.

Figure 1. Body mass index as a function of the physical activity level at baseline (A) and at follow up (B).

Linear regression analysis shows an inverse relationship at baseline (A, continuous line) and no relationship at follow-up (B, discontinuous line), 11±4 yr later, in 40 subjects.

Figure 2. Change in fat mass as a function of the difference in physical activity level.

Physical activity level at baseline (PAL₁) and at follow up (PAL₂), 11±4 yr later, in 40 healthy subjects with body-mass indices within the normal range. Linear regression shows an inverse relationship between the change in PAL and the rate of fat mass change.