Eating during the night increases the levels of blood glucose, while eating only during the daytime may prevent prevents the rise in blood glucose in night shift workers, suggests a new NIH study reported in the journal Science Advances.¹

Nineteen healthy young adults - seven women and 12 men - were recruited for the study. The average age of the participants was 26.5 years, BMI was 22.7 kg/m2 and the hemoglobin A1c ranged between 4.9 to 5.4%. The participants were randomized to a 14-day strict controlled laboratory protocol involving simulated night work conditions with either day time eating or nighttime eating mimicking the eating schedule of night shift workers. The researchers then examined the effects of meal timing on the “central (body temperature) and peripheral (glucose and insulin) endogenous circadian rhythms”.

A marked difference in the blood glucose levels was noted between the two groups. Levels of blood glucose increased by an average of 6.4% among those participants engaged in simulated night work and nighttime eating, whereas eating during the daytime only did not show any significant rise.

Nighttime eating boosted glucose levels, while restricting meals to the daytime prevented this effect in this study, which is the first to show that the meal timing intervention significantly modified the impact of simulated night work on the risk of diabetes and obesity.

The researchers have put forth circadian misalignment between the central and peripheral clocks as a possible explanation for the effect of nighttime eating on glucose levels seen among night shift workers. They state, “The mistiming between the central circadian “clock” and behavioral sleep/wake, light/dark, and fasting/eating cycles, which can influence peripheral “clocks” throughout the body.”

Night shift workers are at risk of type 2 diabetes and obesity. Hence, meal timing may be a potential lifestyle behavioral intervention among night shift workers to counter “the combined negative effects of impaired glucose tolerance and disrupted alignment of circadian rhythms resulting from simulated night work”, according to the lead author of the study,  Frank A.J.L. Scheer, Ph.D., and director of the Medical Chronobiology Program at Brigham & Women’s Hospital in Boston and professor of medicine at Harvard Medical School.

Reference

1. Chellappa SL, et al. Daytime eating prevents internal circadian misalignment and glucose intolerance in night work. Sci Adv. 2021 Dec 3;7(49):eabg9910. doi: 10.1126/sciadv.abg9910.