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 kg m(-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+/-11.4 mm day(-1) in C, whereas EI decreased by 130+/-485 kcal day(-1) and there was no change in subjective appetite (0.4+/-9.6 mm day(-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.