Effects of fasted exercise on ad libitum 24 h energy intake

Objective: Exercise in the fasted state (overnight fast) shifts fuel utilization towards increased fat oxidation. However, the effects on weight loss are equivocal. While breakfast omission may help reduce 24 h energy intake, we and others have shown that hunger is increased and (partial) compensation of the omitted breakfast occurs at subsequent meals on the same day. The present study aimed to investigate the effects of fast- ed vs. non-fasted exercise on 24 h ad libitum energy intake. Methods: In this crossover study, 24 healthy participants (25.7 ± 3.6 years, 22.5 ± 2.0 kg/m2, 54% men, regular habitual exercise, regular breakfast consumption) completed two identical 30-min aerobic exercise sessions (vigorous intensity, average energy expenditure: 309 ± 100 kcal) at least 3 days apart. The exercise sessions occurred following (1) an overnight (12 h) fast (FE) or (2) a standardized breakfast (BE; oatmeal, low-fat milk, and apple; ~10 – 15 % of individual daily energy requirements) after an overnight fast. Participants in FE were offered the same breakfast 30 min after completing the exercise session; however, consumption was voluntary. Total 24 h energy intake, as well as energy intake at breakfast, lunch, and dinner, were assessed for both exercise days via a weighed food log. Snacks in between meals were added to the closest main meal (depending on the time of consumption). Results: Total 24 h energy intake did not differ between FE (2146 ± 758 kcal) and BE (2025 ± 723 kcal, P = 0.316). However, when looking at individual meals, we found a significant difference in energy intake at breakfast (FE: 541 ± 445 kcal vs. BE: 334 ± 183 kcal, P = 0.023) and lunch (FE: 598 ± 289 kcal vs. BE: 801 ± 403 kcal, P = 0.022), but not at dinner (FE: 1007 ± 481 kcal vs. BE: 889 ± 515 kcal, P = 0.144). Conclusion: In the present study, despite perturbations of meal size immediately after fasted exercise, total ad libitum 24 h energy intake did not differ compared to fed exercise.     «

Objective: Exercise in the fasted state (overnight fast) shifts fuel utilization towards increased fat oxidation. However, the effects on weight loss are equivocal. While breakfast omission may help reduce 24 h energy intake, we and others have shown that hunger is increased and (partial) compensation of the omitted breakfast occurs at subsequent meals on the same day. The present study aimed to investigate the effects of fast- ed vs. non-fasted exercise on 24 h ad libitum energy intake. Meth...     »