After a long day, nighttime snacking might feel like the ultimate way to unwind. But a new study suggests that skipping that pre-bedtime nosh could benefit your cardiometabolic health. Specifically, researchers found that fasting for at least three hours before bedtime was linked to improvements in markers such as blood pressure and insulin function.1

Examining Overnight Fasting Routines

Having optimal cardiometabolic health—how well your heart, blood vessels, and metabolism are functioning together—is rare in the United States; one estimate suggests only about 7% of adults meet the criteria.2 While it’s well known that what you eat affects heart health and metabolic health risk factors, growing research suggests that when you eat also matters.

Late-night eating, for example, has been linked to worse cardiometabolic outcomes, while time-restricted eating—limiting food intake to certain hours of the day—has been associated with improvements.3 

For the new study, published in February in the journal Arteriosclerosis, Thrombosis, and Vascular Biology, researchers wanted to test what would happen when people aligned fasting with personal sleep patterns, said Daniela Grimaldi, MD, PhD, first author of the new study and a research associate professor of neurology at Northwestern University Feinberg School of Medicine.

To explore this approach, Grimaldi and her colleagues designed a seven-and-a-half-week study that included 39 adults with overweight or obesity. Participants were split into two groups: one fasted for 13 to 16 hours overnight, while the control group fasted for 11 to 13 hours. Both groups also stopped eating and dimmed the lights three hours before bedtime, timing their last meal or snack with their individual sleep schedules.

What Researchers Found

Compared to the control group, those who fasted for a longer period overnight experienced significant improvements in their diastolic blood pressure levels, and also had better glucose tolerance and insulin function, lower nighttime heart rate, and less nighttime cortisol.

“The key message from this study is that there appears to be some cardiometabolic benefit to extending overnight fasting by three hours with the last meal of the day being three hours prior to sleep,” said Sabrina Islam, MD, MPH, a cardiologist and associate professor of medicine at Temple University’s Lewis Katz School of Medicine who was not involved in the research. “It’s not only the duration of eating restriction that matters but also the timing of meals.” 

According to Grimaldi, it’s possible that eating late at night may interfere with your body’s preparation for sleep—a rise in melatonin and a slowing of metabolic rate and nervous system activity—that helps regulate blood pressure, heart rate, and blood sugar. Disrupting these processes could have a negative effect on cardiometabolic health.

Should You Stop Eating Three Hours Before Bed?

Before making pre-bedtime fasting a habit, it’s important to understand the study’s limitations.  

Most participants were women, which means the findings may not be broadly applicable, particularly since sex differences can influence hormonal, metabolic, and sleep processes. Although researchers accounted for factors like physical activity and light exposure, subtle variations in those behaviors could still have affected the results. And because the study lasted just 7.5 weeks, it’s unclear how nighttime fasting might influence metabolic health over the long term.

Even so, Grimaldi recommends finishing your last meal or snack about three hours before bed and aiming for an overnight fasting window of 13 to 16 hours. Gradually easing into those changes can make them easier to stick to, she said. 

It’s also wise to consult a physician before significantly changing your dietary habits. Some people, such as those with irregular blood pressure or blood sugar levels, may need a more tailored approach to avoid unwanted side effects, Islam noted. “Individualizing this advice for each person based on their schedule allows for improved success in implementation of this recommendation,” she said.