Adaptations to exercise in compensators and non-compensators in the E-MECHANIC Trial.

PURPOSE Rating of Perceived Exertion (RPE) and respiratory exchange ratio (RER) have previously been associated with acute exercise compensation. This study examined adaptations in RPE and RER with long-term exercise training in individuals who did (non-compensators) and did not (compensators) lose the expected amount of weight. METHODS Participants (n = 110, 71.8% F, mean ± SD age 49 ± 12 years) completed 24 weeks of supervised exercise training at 65-85% VO2peak to achieve a prescribed dose of 8 kcal/kg body weight/week (8 KKW) or 20 KKW. Participants were categorized as non-compensators (n=55) or compensators (n=55) based on the percent of expected weight loss (%EWL) achieved. Changes in RPE and RER during exercise over time (baseline, week 12, week 24) were compared by weight compensation category. Individual %EWL in relation to RPE, RER, and training intensity (%VO2peak) was evaluated over the same time period. RESULTS RPE and RER for a given workload decreased from baseline to week 12 and stabilized through week 24, regardless of weight compensation (time p<0.0001). Non-compensators had a higher RPE relative to heart rate, which was partly explained by higher %VO2peak. RPE and %VO2peak both positively predicted %EWL, independent of age, sex, and exercise dose. CONCLUSION Training intensity and RPE were positively associated with weight loss on the individual level, warranting further investigation into self-selection in exercise-based programs. Understanding individual heterogeneity in training intensity and behavioral responses may improve future weight management efforts that involve exercise.