Matching energy intake to expenditure of isocaloric exercise at high- and moderate-intensities

Abstract

BackgroundThose seeking to manage their bodyweight use a variety of strategies, but the most common approaches involve attempting to exercise more and/or consume fewer calories. A poor comprehension of the energy cost of exercise and the energy content of food may contribute to weight-gain and the poor success rate of exercise weight-loss interventions. PurposeThe purpose of this study is to investigate individuals' ability to consciously match energy intake with energy expenditure after isocaloric exercise at moderate and high intensities. MethodIn a counterbalanced cross-over study design, 14 low- to moderately-active, lean individuals (7 male, 7 female; mean age 23±3years; mean BMI 22.0±3.2kg·m−2) completed both a moderate-intensity (60% VO2max, MOD) and a high-intensity (90% VO2max, HIGH) exercise bout on a treadmill, matched for energy expenditure, EE (450kcal). Participants were blinded to the intensity and duration of each bout. Thirty minutes post-exercise, participants were presented with a buffet, where they were asked to consume food in an attempt to match energy intake with the energy expended during the exercise bout. This was termed the “matching task,” providing a matching task energy intake value (EIMATCH). Upon finishing the matching task, a verbal estimate of energy expenditure (EST) was obtained before the participant was allowed to return to the buffet to consume any more food, if desired. This intake was covertly measured and added to EIMATCH to obtain an ad libitum intake value (EIAD LIB). ResultsA significant condition×task interaction showed that, in MOD, EST was significantly lower than EE (298±156kcal vs. 443±22kcal, p=0.01). In the HIGH condition, EE, EIMATCH and EST were similar. In both conditions, participants tended to over-eat to a similar degree, relative to EST, with EIMATCH 20% and 22% greater than EST in MOD and HIGH respectively. Between-condition comparisons demonstrated that EIMATCH and EST were significantly lower in MOD, compared with HIGH (374±220kcal vs. 530±248kcal, p=0.002 and 298±156kcal vs. 431±129kcal, p=0.002 respectively). For both conditions, EIAD LIB was approximately 2-fold greater than EE. DiscussionParticipants exhibited a strong ability to estimate exercise energy expenditure after high-intensity exercise. Participants appeared to perceive moderate-intensity exercise to be less energetic than an isocaloric bout of high-intensity exercise. This may have implications for exercise recommendations for weight-loss strategies, especially when casual approaches to exercise and attempting to eat less are being implemented.