The Impact of Prescribed Exercise and Short-Term Caloric Restriction on Moderate-to-Vigorous Physical Activity (P08-011-19)

Abstract

ObjectivesWeight loss, especially when achieved by caloric restriction (CR), reduces total daily energy expenditure (EE), which can attenuate further weight loss. Although exercise is a common countermeasure to the decline in EE, it is unknown whether prescribed exercise leads to compensatory changes in moderate-to-vigorous physical activities (MVPA) during non-exercise periods in the context of CR. The present study sought to quantify changes in MVPA in response to an energetically-matched energy deficit induced by CR alone or combined with exercise. We hypothesized that MVPA outside of prescribed exercise would be greater during non-exercise conditions, regardless of energy balance. MethodsIn a repeated-measures crossover design, active men (n = 6, 25 ± 1.0 y) underwent four 4-day conditions: CR with exercise (CR + X), CR without exercise (CR–X), energy-balanced control (CON) with exercise (CON + X) and without exercise (CON–X). Dietary intake was manipulated such that energy availability (EA) was 15 kcal·kg FFM−1·day−1 (CR) or 40 kcal·kg FFM−1·day−1 (CON). Prescribed exercise EE was 15 kcal·kg FFM−1·day−1. Physical activity was assessed using the SenseWear Pro3 armband (Bodymedia, Pittsburgh, USA) to quantify time spent in MVPA and light activities (sleep, lying down without sleep, and non-lying light activities) as % of total wear time. ResultsEA did not differ between CR (P = 0.87) nor CON (P = 0.42). As expected, weight loss was significant (P < 0.001) in CR + EX (–1.8 ± 0.4 kg) and CR-EX (–2.4 ± 0.3 kg). After deducting prescribed exercise, there was a significant effect of exercise on time spent in MVPA (P = 0.02), in that MVPA was lower during CON-EX vs. CON + EX (11.4 ± 2.0% vs. 17.9 ± 2.1%, P = 0.03) and trended lower during CR-EX vs. CR + EX (13.6 ± 1.5% vs. 15.5 ± 1.6%, P = 0.08). In exercise conditions, MVPA was lower during CR + EX when compared to CON + EX (P = 0.03). ConclusionsIndependent of energy balance, engaging in short-term exercise led to more, not less, time spent in non-exercise MVPA. These findings indicate the prevention of reductions in non-exercise activity as an additional benefit of incorporating exercise into weight loss interventions. Funding SourcesThe study was supported in part by the USDA National Institute of Food and Agriculture and institutional funding from the University of Nebraska-Lincoln.