Intermittent fasting does not uniformly impact genes involved in circadian regulation in women with obesity

Abstract

Objective: This study aimed to examine the effects of intermittent fasting (IF) on mRNA levels of peripheral clock genes in skeletal muscle and subcutaneous adipose tissue (SAT) in women with obesity. Methods: Women were randomized to one of two IF protocols and pro-vided with all foods at 100% or 70% of calculated weekly energy require-ments for 8 weeks. Breakfast was consumed before a 24-hour fast, which was initiated on three nonconsecutive days per week. Muscle and SAT biopsies were performed at 8 AM after an overnight fast at baseline and at week 8 on a refed day and again following a 24-hour fast at week 8 for analysis of the mRNA levels of key genes involved in circadian regulation. Results: A group-by-time interaction was observed in Per2 in muscle (F = 3.497, P = 0.044) and SAT (F = 6.686, P = 0.008), but significance was lost upon post hoc adjustment. A time effect was observed in Rora in muscle, which was decreased by refeeding in both groups (F = 7.225, P = 0.003). Conclusions: There was no universal effect of IF to alter peripheral clocks, which may be partly because of the alignment of the fasting/feeding cycle with the biological clock. Optimizing intermittent fasting protocols could be important to prevent circadian misalignment in humans.