Early Time-restricted Eating Reduces Sleep Duration And Subjective Alertness In Healthy Adults

INTRODUCTION: Eating across an extended period of the day is associated with obesity, possibly related to the influence of later timing of energy intake on sleep. Early time-restricted eating (eTRE) is a dietary strategy that restricts energy intake to a 6-10 h period beginning in the morning and is associated with cardiometabolic benefits and weight loss. However, the impact of eTRE on sleep duration, sleep quality and subjective alertness have not been examined. PURPOSE: To determine the impact of 1 week of eTRE in healthy, young men and women on sleep duration, sleep quality and subjective alertness. METHODS: Thirteen healthy adults (8F, 26.9 ± 3.9 years, BMI: 23.3 ± 2.1 kg/m2; mean ± SD) participated in a 2w protocol using a consecutive design. During Week 1, energy was consumed over a 13 h period with meals individually anchored to habitual waketime with breakfast, lunch, dinner, and snack consumed at +1 h, +6 h, +11 h, +14 h after waketime. In Week 2, participants were instructed to match food intake from Week 1 but restrict intake to an 8 h period with meals at +1 h, +5 h, and + 9 h after waketime. Participants were instructed to maintain 8 h sleep throughout the 2-week protocol. Participants wore actiwatches throughout the study to assess total sleep time (TST), time in bed (TIB), sleep efficiency (SE; defined as [TST/TIB]*100), sleep onset latency (SOL), wake after sleep onset (WASO), and number of awakenings. At the end of each week, participants were admitted to the laboratory for an in-patient overnight stay. Visual analogue scales (VAS) were administered within 10 min of waking in the laboratory to assess subjective ratings of alertness. RESULTS: Compared with one week of typical eating, eTRE was associated with a significant reduction in TST (7.05 ± 0.08 v 6.82 ± 0.11 h; p = 0.04; mean ± SEM); and SE (88.4 ± 0.8% v 85.5 ± 1.2%; p = 0.01) in healthy adults. No changes were observed in TIB, SOL, WASO or number of awakenings. Additionally, one week of eTRE was associated with significantly lower subjective alertness upon waking (p < 0.05) as compared with habitual eating. CONCLUSION: This is the first report that eTRE is associated with objectively measured reductions in sleep duration. Future research is needed to determine whether elevated hunger and appetite prior to sleep onset leads to reduced sleep duration and efficiency during eTRE.