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.<br /><br />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.<br /><br />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.
Westerterp, K. R., & Plasqui, G. (2009). Physically active lifestyle does not decrease the risk of fattening. PLoS ONE, 4(3). https://doi.org/10.1371/journal.pone.0004745