Timing of food intake during simulated night shift impacts glucose metabolism: A controlled study

ABSTRACT

Eating during the night may increase the risk for obesity and type 2 diabetes in shift workers. This study examined the impact of either eating or not eating a meal at night on glucose metabolism. Participants underwent four nights of simulated night work (SW1–4, 16:00–10:00 h, <50 lux) with a daytime sleep opportunity each day (10:00–16:00 h, <3 lux). Healthy males were assigned to an eating at night (NE; n = 4, meals; 07:00, 19:00 and 01:30 h) or not eating at night (NEN; n = 7, meals; 07:00 h, 09:30, 16:10 and 19:00 h) condition. Meal tolerance tests were conducted post breakfast on pre-night shift (PRE), SW4 and following return to day shift (RTDS), and glucose and insulin area under the curve (AUC) were calculated. Mixed-effects ANOVAs were used with fixed effects of condition and day, and their interactions, and a random effect of subject identifier on the intercept. Fasting glucose and insulin were not altered by day or condition. There were significant effects of day and condition × day (both p < 0.001) for glucose AUC, with increased glucose AUC observed solely in the NE condition from PRE to SW4 (p = 0.05) and PRE to RTDS (p < 0.001). There was also a significant effect of day (p = 0.007) but not condition × day (p = 0.825) for insulin AUC, with increased insulin from PRE to RTDS in both eating at night (p = 0.040) and not eating at night (p = 0.006) conditions. Results in this small, healthy sample suggest that not eating at night may limit the metabolic consequences of simulated night work. Further study is needed to explore whether matching food intake to the biological clock could reduce the burden of type 2 diabetes in shift workers.

KEYWORDS:

• metabolism
• insulin
• glucose
• night shift
• sleep restriction
• sleep loss

Acknowledgments

The authors would like to thank the research staff and students for their contributions. In particular; Stephanie Centofanti, Emily Watson, Cassie Hilditch, Alex Agostini, Alex Chatburn, Katja Morsky, Kenji Sison, students and volunteers. Thank you also to all the participants.

Funding

Funding for this study was obtained through internal competitive university grant schemes. The two PhD students (CG, MP) working on this study were funded through Australian Postgraduate Awards.

Additional information

Funding

Funding for this study was obtained through internal competitive university grant schemes. The two PhD students (CG, MP) working on this study were funded through Australian Postgraduate Awards.