June 16, 2020
Eating a late dinner alters metabolic markers during sleep in a way that could lead to obesity or diabetes, according to the results of a small randomized crossover clinical trial, the Effect of Late Dinner on Nocturnal Metabolism.
Specifically, 20 healthy young adult volunteers made two 3-day visits to a clinical research unit, where they had fixed meals, fixed sleeping times, and serial blood draws under two different conditions: regular dinner (6 PM) or late dinner (10 PM).
The results showed that having a late dinner "induces nocturnal glucose intolerance, and reduces fatty acid oxidation and mobilization, particularly in earlier sleepers," Chenjuan Gu, MD, PhD, Johns Hopkins University, Baltimore, Maryland, and colleagues report in a study published online June 11 in the Journal of Clinical Endocrinology & Metabolism.
This research "sheds new light on how eating a late dinner worsens glucose tolerance and reduces the amount of fat burned," senior author Jonathan C. Jun, MD, from the same university, said in a statement issued by the Endocrine Society.
"If the metabolic effects we observed with a single meal keep occurring chronically," he added, "then late eating could lead to consequences such as diabetes or obesity."
"We still need to do more experiments to see if these effects continue over time, and if they are caused more by behavior (such as sleeping soon after a meal) or by the body's circadian rhythms."
Growing Evidence of Growing Girth With Late Dinner
Accumulating evidence suggests the time that meals are eaten can influence the development of obesity and metabolic syndrome, Gu and colleagues write.
However, most studies of meal timing have not controlled for sleep time or examined detailed metabolic responses to meal timing, which would help "to inform the design of clinical trials to discover the ideal timing and composition of meals to combat obesity, metabolic syndrome, and diabetes," they explain.
Because sleep lowers the metabolic rate, researchers hypothesized that eating dinner close to bedtime would lead to postprandial hyperglycemia and lower dietary fat oxidation.
To investigate this, they recruited 10 male and 10 female healthy nonobese adults without diabetes, who were 18 to 30 years old, did not have sleep problems, and usually went to sleep between 10 PM and 1 AM.
The participants were a mean age of 26, had a mean body mass index of 23 kg/m2, and were mainly Asian (11 participants) or white (8 participants), with only one Hispanic and one African American participant.
They were admitted to the clinical research unit for two visits (late dinner or regular dinner) 3 to 4 weeks apart in a random order.
On day 1 (acclimatization), they were admitted in the evening and slept overnight.
On day 2 (test day), they could engage in sedentary activities and were given four standardized meals, including a dinner with a stable isotope of palmitate, used to measure fat oxidation overnight. They had 20 hourly blood draws, from 5 PM until noon the following day. That night they had polysomnography.
On day 3, they had a fixed breakfast and left after the noon blood draw.
The participants also had a dual-energy X-ray absorptiometry (DEXA) scan to estimate fat mass.
Their meals on the test day provided 2100 calories (25% at breakfast, 30% at lunch, 35% at dinner, and 10% in a snack), and each meal consisted of 50% carbohydrates, 35% fat, and 15% protein.
They ate breakfast at 8 AM and lunch at 1 PM, and either had dinner at 6 PM and a snack at 10 PM (regular dinner) or had a snack at 6 PM and dinner at 10 PM (late dinner).
They all slept from 11 PM to 7 AM.
Almost 20% Higher Glucose, 10% Less Fat Burned, After Late Dinner
After the late dinner, participants had higher glucose, a delay in the triglyceride peak, lower free fatty acid mobilization, reduced dietary fatty acid oxygenation, and increased evening cortisol, and those who usually went to bed early (10 PM) were more likely to have metabolic dysfunction.
"On average," Gu noted in the statement, "the peak glucose level after late dinner was about 18% higher, and the amount of fat burned overnight decreased by about 10% compared to eating an earlier dinner."
Moreover, "the effects we have seen in healthy volunteers might be more pronounced in people with obesity or diabetes, who already have a compromised metabolism,” and further work will be needed, he concluded.
The study was funded by grants from the National Institutes of Health and a fellowship from the American Heart Association. The authors have reported no relevant financial relationships.