Clinical Nutrition · Sep 2, 2026

Late-timed eating alters the diurnal pattern of fuel selection and lowers metabolic flexibility without changing 24-hour energy expenditure: A randomized crossover trial

By Hatamoto Y, Tanoue Y, Yoshimura E et al.

BACKGROUND & AIMS: Meal timing may influence energy expenditure (EE) and metabolic responses. However, the effects of different meal-timing schedules on free-living physical activity, 24-h EE, respiratory exchange ratio (RER), and metabolic flexibility under matched energy intake and meal composition remain unclear. METHODS: In a randomized two-period crossover trial, eight healthy young men were allocated in a 1:1 ratio to either an early-to-late or late-to-early meal-timing sequence, with a washout period of at least 1 week between conditions. Participants followed each meal schedule for 7 days and stayed in a whole-room calorimetry chamber from the evening of Day 7 to the morning of Day 9. Identical meals were provided under both conditions, with matched energy intake, meal composition, fasting duration, and sleep-wake timing. Twenty-four-hour EE and RER were assessed from the morning of Day 8 to the morning of Day 9, while free-living physical activity and accelerometer-derived activity-related EE were assessed on Days 1-6. RESULTS: Accelerometer-derived estimates of activity-related EE during the free-living period did not differ between the early- and late-timed eating conditions (651 ± 112 vs. 656 ± 178 kcal/d, P = 0.922), and no significant differences were observed in 24-h step counts or time spent in different activity-intensity categories. Total 24-h EE did not differ significantly between early and late meal timing conditions (1879 ± 194 vs. 1856 ± 229; p = 0.489). Although the 24-h mean RER was slightly higher in the late-timed condition (0.895 ± 0.019) than in the early-timed condition (0.879 ± 0.017), the difference did not reach statistical significance (p = 0.106, effect size d = 0.832). In contrast, RER during the sleep period (00:00-07:59) was significantly higher in the late-timed condition (0.897 ± 0.017) compared to early-timed eating (0.838 ± 0.027; p < 0.001). Moreover, the amplitude of 24-h RER variation-used as a surrogate for metabolic flexibility-was significantly lower with late-timed eating (0.131 ± 0.021 vs. 0.194 ± 0.030; p < 0.001). CONCLUSION: In this 8-day controlled meal-timing intervention, late-timed eating did not alter free-living physical activity or accelerometer-derived activity-related EE, nor did it alter 24-h EE measured in the room chamber. However, it was associated with a higher sleep-period RER and a smaller 24-h RER range, consistent with lower metabolic flexibility and an attenuated overnight shift in fuel selection from carbohydrate toward fat.

doi.org/10.1016/j.clnu.2026.106771PubMed 42945603Interventions