The Adaptive Metabolic Response to Exercise-induced Weight

34 35 Background: A decline in resting energy expenditure (REE) beyond that predicted from 36 changes in body composition has been noted following dietary-induced weight loss. 37 However, it is unknown whether a compensatory down-regulation in REE also accompanies 38 exercise-induced weight loss, or whether this adaptive metabolic response influences energy 39 intake (EI). Methods: Thirty overweight and obese women (BMI = 30.6 ± 3.6kgm) 40 completed 12 weeks of supervised aerobic exercise (EX). Body composition, metabolism, EI 41 and metabolic-related hormones were measured at baseline, week six and post-intervention. 42 The metabolic adaptation i.e. difference between predicted and measured REE was also 43 calculated post-intervention (MApost), with REE predicted using a regression equation 44 generated in an independent sample of 66 overweight and obese women (BMI = 31.0 ± 45 3.9kgm). Results: While mean predicted and measured REE did not differ post46 intervention, 43% of participants experienced a greater than expected decline in REE (-102.9 47 ± 77.5kcalday). MApost was associated with the change in leptin (r = 0.47; p = 0.04), and the 48 change in resting fat (r = 0.52; p = 0.01) and carbohydrate oxidation (r = -0.44; p = 0.02). 49 Furthermore, MApost was also associated with the change in EI following EX (r = -0.44; p = 50 0.01). Conclusions: Marked variability existed in the adaptive metabolic response to EX. 51 Importantly, those who experienced a down-regulation in REE also experienced an up52 regulation in EI, indicating that the adaptive metabolic response to exercise influences both 53 physiological and behavioural components of energy balance. 54