Influence of exercise-induced energy deficit on non-exercise activity thermogenesis in overweight and obese adults

Energy balance is a dynamically regulated system and perturbing one of its components (reduction in energy intake (EI) or increase in energy expenditure (EE)) can result in biological and behavioural compensatory responses of unpredictable magnitude elsewhere in the system (Casanova et al., 2019, Proceeding of the Nutrition Society, 1-11). In fact, exercise induced EE can elicit compensatory changes in EI and/or non-exercise activity thermogenesis
(NEAT), that consequently attenuate the energy gap between EI and EE. Although compelling evidence suggests that exercise-mediated changes in NEAT seem to be subject to large interindividual variance, research investigating the impact of biological sex on exercise-induced modulation of NEAT is lacking (Doucet, McInis and Mahmoodianfard, 2018, Obesity Reviews,
19, 36-46). Therefore, the aim of this study was to investigate the effect of an exercise-induced energy deficit on NEAT in overweight and obese men and women. With institutional ethics approval, over 21 days, four men (mean ± SD; age 30.3 ± 8.3 years; body mass, 96.9 ± 12.8kg; BMI, 28.4 ± 2.1 kg·m²) and six women (age 23.0 ± 2.1 years; body mass, 79.9 ± 8.6 kg; BMI, 29.1 ± 2.5 kg·m²) completed 3 sequential phases each lasting 7 days. During the second phase, participants visited the lab on 3 separate days to expend 15% of their total-daily EE in each visit via steady-state cycling at moderate-intensity. Throughout the study period, NEAT
was assessed using a commercially available accelerometer worn at the wrist, whereas body composition was analysed via bioelectrical impedance on the 1st and 21st day. Group
differences in descriptive characteristics were analysed using unpaired t-tests. NEAT from each phase were analysed using a 3 x 2 (Time x Sex) mixed model ANOVA, whereas body mass from the pre-measurement and post-measurement days were analysed through unpaired t-tests. At baseline, men had greater stature (mean difference = 18.6 cm; P = 0.021), body mass (mean difference = 17.1 kg; P = 0.035) and basal metabolic rate (mean difference = 2796 kJ; P = 0.01) than women. By contrast, women’s body fat percentage was greater than men (P = 0.004). There were no differences in BMI (P = 0.694), body mass percentage change
(P = 0.409) and exercise-induced EE (mean difference = 495 kJ, P = 0.91) between men and women. Furthermore, there was no main effect of time (P = 0.613), or sex (mean difference = 4 %, P = 0.470), for NEAT. Lastly, there was no interaction between sex and time (P = 0.806). These results suggest that an acute exercise-induced perturbation of energy balance does not elicit changes in NEAT that could hinder body mass loss in both men and women.