Slight weight loss observed in night-shift workers fasting during overnight hours
Night-shift workers in Australia who were able to rearrange their meal times and fast during overnight hours had a small decrease in weight, according to data published in Nutrition, Metabolism & Cardiovascular Diseases.
“‘Shifting the Risk’ is the first study to examine the effects of a meal-timing intervention on cardiovascular disease risk markers in night-shift workers,” Maxine Bonham, PhD, an associate professor in the department of nutrition, dietetics and food at Monash University in Melbourne, Australia, and colleagues wrote. “We showed that it is feasible for night-shift workers to maintain a small 5-hour overnight fast. Adherence to the 1 a.m. to 6 a.m. fast was high during the 4-week intervention period, with only three episodes of nonadherence reported and only one participant withdrawing due to inability to maintain the fasting period.”
Researchers conducted a randomized crossover trial with 19 night-shift workers in Melbourne, Australia (13 women; mean age, 41 years; age range, 18-60 years), from July 2017 to October 2018. All participants were permanent or rotating night-shift workers who had worked the night shift for at least 1 year before enrollment and had abdominal obesity.
Before the start of the study, participants were asked to keep a 4-day food diary that included at least two night shifts to document their typical food intake. Participants were then randomly assigned to an intervention group asked to fast between 1 a.m. and 6 a.m. or a control group maintaining their normal dietary habits for 4 weeks. Both groups were asked to not change their physical activity habits or the type of food they consumed. Adherence was confirmed through a weekly 24-hour dietary recall. After a 2-week washout period, participants switched to the opposite group and were in the intervention or control group for an additional 4 weeks. An acute meal challenge was conducted at baseline and the end of both study periods, when data on postprandial triglyceride response, glucose, insulin and body weight were collected.
Slight weight loss with overnight fast
Fasting triglyceride, glucose and insulin levels remained in the healthy range during the control and intervention periods, with no significant differences between them. Both control and intervention participants had similar postprandial triglycerides responses at their challenge sessions. Postprandial and peak glucose concentrations and insulin concentration were also similar between the intervention and control periods. A slightly lower mean body weight was observed at the end of the intervention period vs. control (mean difference, –0.9 kg; 95% CI, –1.3 to –0.4; P < .001). There were no differences in physical activity between the two groups.
“Our pilot data suggests that reducing the number of eating occasions during the night may promote a small shift in body weight, which may be related to lowered thermic effect of food observed during the night,” the researchers wrote.
Good adherence to overnight fast
During the intervention period, 73 dietary recalls were collected, whereas 68 were collected during the control period. There were just nine eating occasions documented between 1 a.m. and 5:59 a.m. during the intervention period compared with 112 during the control period. Six of the nine intervention eating occasions occurring during fasting hours took place at exactly 1 a.m., whereas the remaining three were nonadherence episodes. The reasons given for nonadherence were an inability to avoid caffeinated drinks and fresh produce tasting for work purposes.
Eating occasions were low between 10 a.m. and 3:59 p.m. during control and intervention periods, likely due to sleep time for the night-shift workers. During the intervention, participants redistributed most of their overnight eating to immediately before or immediately after the fasting period.
Researchers said more randomized controlled trials should be conducted with larger samples to better analyze the cardiometabolic effects the timing of eating has on night-shift workers.
“Sample size estimations have been provided using data generated, allowing future definitive randomized controlled trials to test whether an overnight fast is able to improve postprandial triglyceride and glucose metabolism in night-shift workers,” the researchers wrote. “For future meal-timing interventions examining CVD risk, postprandial triglyceride and glucose response remain appropriate outcome measures to target.”