Effect of exercising while fasting on eating behaviors and food intake.

Background: Alternate day fasting combined with exercise is effective for weight loss.

Objective: The aim of this study was to examine the behavioral adaptations that occur when ADF is combined with exercise, and to determine how these changes affect weight loss.

Design: Obese subjects (n = 64) were randomized to 1 of 4 groups: 1) combination (ADF + endurance exercise), 2) ADF, 3) exercise, or 4) control, for 12 weeks.

Results: Body weight decreased (P < 0.05) in the combination group (6 ± 4 kg), ADF (3 ± 1 kg), exercise group (1 ± 0 kg), with no change in the control group (0 ± 0 kg). When given the choice, subjects chose to exercise the same amount (P = 0.790) on the fast days (48 ± 2%) as feed days (52 ± 2%). Percent of exercise sessions performed on fast day mornings (20 ± 6%) did not differ (P = 0.453) from fast day afternoons (28 ± 5%). Likeliness to cheat on the fast day was not higher if the subject exercised in the afternoon (17 ± 7%) versus the morning (10 ± 5%). Hunger decreased (P < 0.05) while satisfaction and fullness increased (P < 0.05) post-treatment in the ADF group only. Restrained eating increased (P < 0.05) and uncontrolled eating decreased (P < 0.05) in the combination and ADF groups.

Conclusion: These findings suggest that endurance exercise is an excellent adjunct therapy to ADF, as it leads to positive behavioral changes that may contribute to long-term steady weight loss.