Joint associations between objectively measured physical activity volume and intensity with body-fatness. The Fenland Study

Background/ObjectivesPhysical activity energy expenditure (PAEE) represents the total volume of all physical activity. This can be accumulated as different underlying intensity profiles. Although volume and intensity have been studied in isolation, less is known about their joint association with health. We examined this association with body-fatness in a population-based sample of middle-aged British women and men. Methods6148 women and 5320 men from the Fenland study with objectively-measured physical activity from individually calibrated combined heart rate and movement sensing and DXA-derived body-fat percentage (BF%) were included in the analyses. We used linear and compositional isocaloric substitution analysis to examine associations of PAEE and its intensity composition with body-fatness. Sex-stratified models were adjusted for socio-economic and dietary covariates. ResultsPAEE was inversely associated with body-fatness in women (beta=-0.16 (95%CI: -0.17; -0.15) BF% per kJ{middle dot}day-1{middle dot}kg-1) and men (beta=-0.09 (95%CI: -0.10; -0.08) BF% per kJ{middle dot}day-1{middle dot}kg-1). Intensity composition was significantly associated with body-fatness, beyond that of PAEE; the reallocation of energy to vigorous physical activity (>6 METs) from other intensities was associated with less body-fatness, whereas light activity (1.5-3 METs) was positively associated. However, light activity was the main driver of overall PAEE volume, and the relative importance of intensity was marginal compared to that of volume; the difference between PAEE in tertile 1 and 2 in women was associated with 3 percentage-point lower BF%. Higher vigorous physical activity in the same group to the maximum observed value was associated with 1 percentage-point lower BF%. ConclusionsIn this large, population-based cohort study with objective measures, PAEE was inversely associated with body-fatness. Beyond the PAEE association, greater levels of intense activity were also associated with lower body-fatness. This contribution was marginal relative to PAEE. These findings support current guidelines for obesity prevention which emphasise moving more over the specific intensity or duration of that activity.