Silver Spring

Abstract

Objective-This study investigated the effects of circadian misalignment (CM), induced by delaying meal times, independent of sleep timing and duration and eating window duration, on energy expenditure (EE), respiratory quotient (RQ), and substrate oxidation. Methods-Healthy adults, age 20-49 y, participated in this randomized, crossover study under controlled feeding conditions. Eating window duration was identical in both conditions (CA: 0900-1900 h; CM: 1300-2300 h) and bedtimes were constant (2330-0800 h). EE, RQ, and substrate oxidation were obtained over 23 h in a metabolic chamber on days 3-4 and 14-15 in each condition. Twenty-four hour and post-meal outcomes were analyzed using a linear mixed effects model including condition, day, and day-by-condition interaction as main predictors, and sex as a covariate. Results-Three men and four women (age 37.4±8.8 y, BMI 30.4±3.3 kg/m 2) completed the study. Twenty-four-hour EE did not differ between conditions. Post-meal RQ for dinner and snack were higher in CM vs CA (both p<0.001) with correspondingly higher glucose oxidation (both p<0.01) and lower fat oxidation (dinner only p=0.0001). Conclusions-CM, induced by delaying mealtimes by 4 h relative to CA, independently shifts nutrient metabolism towards greater carbohydrate and lower fat oxidation.