Consuming meals too close to bedtime has long been associated with difficulties in regulating blood sugar, potentially increasing the risk of type 2 diabetes, obesity, and heart disease. But what if you simply delay your bedtime after a late dinner? A recent study sheds light on this question.

According to the findings, delaying sleep after a late meal does not mitigate the negative impact on blood sugar and insulin levels. The critical factor appears to be the alignment of meal timing with your body’s circadian rhythm, or internal clock, according to Daisy Duan, MD, an endocrinologist at Johns Hopkins Medicine.

“it still appears it is best to avoid eating a late dinner, even if you don’t go to sleep right after,” says Dr. Duan.

the Impact of Early vs. Late Dinners on Blood Sugar

To investigate this, dr. duan and her team conducted a study involving 13 healthy adults with an average age of 25. The participants were closely monitored in a sleep lab.

Researchers steadfast the start of each participant’s “biological night” by measuring melatonin levels in their saliva. Melatonin, a hormone that promotes sleep, is naturally produced in response to darkness.

According to Dr. Duan, monitoring melatonin levels is the “gold standard” for assessing a person’s circadian rhythm. Researchers measured glucose and insulin levels hourly for 24 hours via IV.

The study involved three scenarios:

• Eating dinner three hours before the start of their biological night, followed by sleep five hours later.
• Eating dinner one hour after the start of their biological night, followed by sleep one hour later.
• eating dinner one hour after the start of their biological night, followed by sleep five hours later.

In all scenarios, participants slept for eight hours and reported similar sleep quality. All participants consumed identical meals, with calorie counts adjusted based on individual weight.

The researchers found that blood glucose levels four hours after dinner were, on average, 11 percent higher in both late-dinner scenarios compared to the early-dinner scenario. Delaying sleep had no significant impact on these levels.

“it still appears it is best to avoid eating a late dinner, even if you don’t go to sleep right after,”

Limitations of the Research

Dr. Duan and her team acknowledge that these findings are preliminary and have not yet undergone peer review or publication in a medical journal.

Ajaykumar Rao, MD, a diabetes and metabolism endocrinologist at Temple Health in Philadelphia, who was not involved in the study, points out that the study’s small sample size (13 adults) and controlled environment may not accurately reflect real-world behaviors. Additionally, the study’s short duration may not capture the long-term effects of late eating or sleeping.

Dr. Rao believes the findings are more relevant to diabetes prevention in healthy young adults rather than lifestyle changes for those already diagnosed with diabetes.

“The results suggest that the cumulative effects of eating late put people at risk for eventually developing insulin resistance,which is a precursor to diabetes,” says Dr. Rao.

“When you eat later, your body’s response to a glucose load might potentially be a bit dampened as your own insulin levels are not attacking that meal the same way they would or else,” he says.

aligning Meals with Your Circadian Rhythm

according to Theresa Gentile, RDN, a spokesperson for the Academy of Nutrition and dietetics, this study underscores the importance of aligning with your body’s natural circadian clock.

“You should try to pay attention to your body’s natural rhythms by noting when you start to feel sleepy in the evening,” says Gentile, who was not involved in the research. “Aim to finish dinner at least a few hours before this time.”

Gentile suggests tracking sleep and hunger patterns with the help of a registered dietitian-nutritionist or using wearable sleep trackers to identify the start of your biological night and optimize meal timing.