Effects of macronutrient manipulation on postprandial metabolic responses in overweight males with high fasting lipids during simulated shift work: A randomized crossover trial

Background & aims: Meals consumed out of synchronisation with normal circadian rhythms are associated with metabolic dysregulation. Changes in macronutrient composition of meals can improve metabolic responses during the day. Therefore, we aimed to investigate whether macronutrient manipulation of meals alters postprandial glucose and lipid responses and the expression of circadian genes during the night. Methods: In a randomised crossover trial, 16 overweight males with high fasting lipids were fed isocaloric meals (2.7 MJ) at 0000 h. The meals differed primarily in total fat and total sugars content (control (8% total sugar, 5% saturated fat) vs test (16% total sugar, 26% saturated fat)). Postprandial blood samples were collected for glucose, insulin (3 h) and triglycerides (6 h) and analysed as incremental area under the curve (iAUC). RNA was extracted at 0 h, 2 h and 4 h and changes in expressions of the circadian genes clock and Per 1–3 analysed. Results: Postprandial glucose (p = 0.04) and insulin iAUC (p = 0.02) were significantly higher after consumption of the test meal compared to the control meal. Postprandial triglyceride iAUC was not statistically different between the two meal types (p = 0.72). No change in circadian gene expression was observed after the two meals. Conclusions: Our results showed that macronutrient composition affects postprandial metabolic response at night. It emphasizes the need to consider the role and effects of night time eating, when developing metabolic disease prevention strategies for shift workers. Study ID number: ACTRN12618001115224. Website of trial registry: http://www.anzctr.org.au/. Retrospectively registered after data collection.