(P15-001-23) Insulin Resistance Following Delayed Mealtimes: A Randomized, Crossover, Controlled Feeding Study

Objectives: In the West, there is a long-term trend of delaying mealtimes which causes discordance with natural day and night environmental cues and results in circadian misalignment (CM). The latter has been adversely associated with anthropometric and metabolic outcomes, yet the underlying mechanisms remain elusive. We aimed to address this knowledge gap.

Methods: This was a randomized crossover trial of two 44-day study phases separated by a 4- to 6-week washout period. Each phase consisted of 15 days of energy-matched controlled feeding followed by 4 weeks of ad libitum feeding. Phases were identical in sleep opportunity (8.5 h) and timing (11:30 PM–8:00 AM), and duration of eating window (10 h); the only difference was in the timing of the eating window and meals relative to sleep. Under circadian alignment (CA), the eating window started 1 h after awakening whereas under CM, it started 5 h after awakening. Half of the participants underwent CA first and the other half underwent CM first. Glucose and insulin concentrations were measured at fasting and every 30 min for 2 h following the breakfast meal in both conditions (9-11 AM in CA; 1-3 PM in CM) on days 4 and 15 of the controlled feeding segment of each phase. We estimated the homeostasis model assessment of insulin resistance (HOMA-IR).

Results: We studied 4 males and 4 pre-menopausal females (62.5% racial/ethnic minority), with mean age 36.8 y (range 24-46 y) and BMI 28.8 kg/m² (range 22.9-33.7 kg/m²). There were no effects of day or day x condition interaction on HOMA-IR. However, there was a significant main effect of condition (p=0.021). Over the study period, mean HOMA-IR values were 2.49 and 3.19 in the CA and CM conditions, respectively (Day 4: 2.19 and 3.18; Day 15: 2.79 and 3.20 in the CA and CM conditions, respectively).

Conclusions: The findings underscore greater insulin resistance under delayed mealtime conditions relative to the sleep period. Our analyses are part of a larger project on mechanisms of the association between CM and cardiometabolic risk, under constant sleep and eating period durations. The findings can improve understanding of the role of sleep and meal coordination in health and guide future research assessing lifestyle strategies for glycemic control personalized to one’s sleep and eating habits.

Funding Sources: NHLBI R01HL142648