Individual variability following 12 weeks of supervised exercise: identification and characterization of compensation for exercise-induced weight loss

Objective: To identify and characterize the individual variability in compensation for exercise-induced changes in energy expenditure (EE). Design: Twelve-week exercise intervention. Subjects: Thirty-five overweight and obese sedentary men and women (body mass index, 31.8 +/- 4.1 kgm(-2); age, 39.6 +/- 11.0 years) were prescribed exercise five times per week for 12 weeks under supervised conditions. Measurements: Body weight, body composition, resting metabolic rate (RMR), total daily energy intake (EI) and subjective appetite sensations were measured at weeks 0 and 12. Results: When all subjects' data were pooled, the mean reduction in body weight (3.7 +/- 3.6 kg) was significant (P < 0.0001) and as predicted, which suggested no compensation for the increase in EE. However, further examination revealed a large individual variability in weight change (-14.7 to +1.7 kg). Subjects were identified as compensators (C) or noncompensators (NC) based on their actual weight loss (mean NC = 6.3 +/- 3.2 kg and C = 1.5 +/- 2.5 kg) relative to their predicted weight loss. C and NC were characterized by their different metabolic and behavioural compensatory responses. Moderate changes in RMR occurred in C (-69.2 +/- 268.7 kcal day(-1)) and NC (14.2 +/- 242.7 kcal day(-1)). EI and average daily subjective hunger increased by 268.2 +/- 455.4 kcal day(-1) and 6.9 +/- 11.4mmday(-1) in C, whereas EI decreased by 130 +/- 485 kcal day(-1) and there was no change in subjective appetite (0.4 +/- 9.6mmday(-1)) in NC. Conclusion: These results demonstrate that expressing the exercise-induced change in body weight as a group mean conceals the large inter-individual variability in body weight and compensatory responses. Individuals who experience a lower than predicted weight loss are compensating for the increase in EE.