Late Dinners Increase Blood Glucose, Could Promote Obesity

Jonathan Jun, MD

While dietary and nutrition science is a hotly-debated subject, the results of a new study suggest eating a late dinner could contribute to high blood sugar and excessive weight gain.

While limited by a relatively small number of patients, the results of the study indicated eating dinner late at night impacts nocturnal glucose intolerance and reduces fatty acid mobilization, which investigators suggest could promote obesity if chronically recurring.

"This study sheds new light on how eating a late dinner worsens glucose tolerance and reduces the amount of fat burned. The effect of late eating varies greatly between people and depends on their usual bedtime," said the study's corresponding author Jonathan C. Jun, MD, associate professor of medicine at the Johns Hopkins University School of Medicine, in a statement. "This shows that some people might be more vulnerable to late eating than others. If the metabolic effects we observed with a single meal keep occurring chronically, then late eating could lead to consequences such as diabetes or obesity."

With the seriousness and prevalence of obesity continuing to rise, Jun and a team of colleagues from the University of Arkansas sought to describe the impact of eating a later dinner on substrate metabolism during sleep. Funded by grants from the National Institutes of Health, investigators designed the current study as a randomized crossover trial in a laboratory setting.

Using a population of 20 healthy volunteers, investigators randomized participants in a 1:1 ratio to a late dinner, which occurred at 22:00, or a routine dinner, which occurred at 18:00. All participants had a fixed sleeping period from 23:00-07:00 in a laboratory setting.

The mean age of patients in the study was 26 years old and the average BMI of participants was 23.2 kg/m2.

The study period lasted a total of 3 days and 2 nights. All participants were on an isocaloric macronutrient diet which contained a dinner representing 35% of a person’s daily kilocalories, 50% of their daily carbohydrates, and 35% of their daily fat intake. Patients were also given an oral lipid tracer with dinner.

The main outcomes measures of the study were nocturnal and next-morning hourly plasma glucose, insulin, triglycerides, free fatty acids (FFAs), cortisol, dietary fatty acid oxidation, and overnight polysomnography. Of note, investigators also calculated sleep/wake activity and active energy through the use of wrist actigraphy.

Upon analysis, investigators found consuming a late dinner was associated with a 4-hour shift in the postprandial period, which overlapped with the sleep phase. Investigators also pointed out the postprandial period following late dinner was characterized by higher glucose levels, triglyceride peak delay, lower FFA, and lower dietary fatty acid oxidation.

Results suggested eating dinner late did not have an impact on sleep architecture but did increase plasma cortisol. Additionally, metabolic changes appeared to be greater in habitual earlier sleepers.

In the aforementioned statement, Jun also highlighted the need for further studies examining the impact of the observed effects over a prolonged period of time. 



"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," Jun said.

This study, “Metabolic Effects of Late Dinner in Healthy Volunteers: A Randomized Crossover Clinical Trial,” was published in the Journal of Clinical Endocrinology & Metabolism.