Abstaining from food for three hours before bedtime and slightly extending the overnight fasting period can help improve blood pressure, heart rhythm, and blood sugar control in adults at risk for cardiometabolic diseases.

The Impact of Meal Timing on Health

Researchers from Northwestern Medicine studied how aligning overnight fasting with the body’s natural sleep-wake cycle can influence heart health and metabolism. Circadian rhythms play a crucial role in regulating cardiovascular and metabolic functions. Notably, the study participants did not reduce their calorie intake—the focus was solely on the timing of meals.

Main Findings of the Study

During the study, middle-aged and older adults at increased risk for cardiometabolic diseases benefited from extending their overnight fasting window by about two hours. They also avoided eating and dimmed the lights three hours before sleep. These changes led to noticeable improvements in heart and metabolic health, both during sleep and the following day.

According to Daniela Grimaldi, a research scientist at the Department of Neurology at Northwestern University Feinberg School of Medicine, synchronizing the fasting window with natural sleep and wake rhythms can enhance coordination between the heart, metabolism, and sleep, which helps protect the cardiovascular system.

The results were published on February 12 in the journal Arteriosclerosis, Thrombosis, and Vascular Biology of the American Heart Association. Phyllis Zee, director of the Center for Circadian and Sleep Medicine, emphasized: “It’s not just what and how much you eat, but also when you eat in relation to sleep that matters for the physiological benefits of time-restricted eating.”

The Importance of Cardiometabolic Disease Prevention

Previous studies show that only 6.8% of adults in the U.S. had optimal cardiometabolic health in 2017–2018. Disruptions in this area increase the risk of chronic diseases such as type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular conditions.

Time-Restricted Eating and Its Features

Time-restricted eating is becoming increasingly popular as research demonstrates its effectiveness in improving cardiometabolic markers, sometimes comparable to traditional calorie-restricted diets. However, most studies have focused on the duration of fasting rather than aligning the fasting window with sleep, which is critically important for metabolic regulation.

Feasibility and Accessibility of the Approach

Nearly 90% of study participants adhered to the protocol, making time-restricted eating tied to the sleep period a realistic and accessible non-pharmacological approach, especially for middle-aged and older adults at higher risk for cardiometabolic disorders. The research team plans to refine the protocol and expand the study through multicenter trials.

Specific Health Improvements Observed

Over 7.5 weeks, researchers compared people who stopped eating at least three hours before bedtime with those who maintained their usual eating habits. The first group showed significant changes: nighttime blood pressure dropped by 3.5%, and heart rate decreased by 5%. These changes reflected a healthier daily rhythm, where pulse and blood pressure rise during the day and fall at night during rest. A more pronounced circadian rhythm is linked to better cardiovascular health.

Participants also demonstrated improved daytime blood sugar control: after glucose intake, the pancreas responded more efficiently, indicating better insulin release and more stable blood sugar levels.

Study Details

The study involved 39 adults aged 36 to 75 with overweight or obesity. Participants were divided into two groups: one extended the overnight fasting window to 13–16 hours, while the other maintained their usual window (11–13 hours). Both groups dimmed the lights three hours before sleep. The group with the longer fasting window was 80% women.

The study was funded by the National Heart, Lung, and Blood Institute, the National Institute on Aging, and the National Center for Advancing Translational Sciences (NCATS).