A new study from Northwestern Medicine suggests that when you stop eating at night may matter just as much as what you eat.
Researchers found that aligning overnight fasting with your natural sleep schedule can improve important measures of heart health and blood-sugar control—without reducing calories.
The study focused on middle-aged and older adults who are at higher risk for cardiometabolic diseases such as heart disease and type 2 diabetes.
Instead of asking participants to eat less, scientists asked them to extend their overnight fasting period by about two hours and to stop eating at least three hours before bedtime.
Participants also dimmed their lights in the evening to support the body’s natural sleep rhythm.
The results showed that this “sleep-aligned fasting” approach improved how the body regulates blood pressure, heart rate, and blood sugar both at night and during the day. Researchers say the key is working with the body’s circadian rhythm—the internal clock that controls sleep, metabolism, and many other processes.
“Our heart, metabolism, and sleep systems are closely connected,” said Dr. Daniela Grimaldi of Northwestern University Feinberg School of Medicine, the study’s lead author. “Timing fasting to match the body’s natural sleep-wake cycle appears to strengthen that coordination and support cardiovascular health.”
The research, published in the journal Arteriosclerosis, Thrombosis, and Vascular Biology, highlights the growing interest in time-restricted eating, a popular approach that limits eating to certain hours of the day. Most previous studies focused on how long people fasted. This study looked instead at whether fasting at the “right” time—before sleep—could bring additional benefits.
Over the 7.5-week study, 39 overweight or obese adults aged 36 to 75 followed either an extended overnight fasting schedule of 13 to 16 hours or their usual routine of about 11 to 13 hours. Those who stopped eating earlier saw notable improvements. During sleep, their blood pressure and heart rate dropped more naturally, a healthy pattern that allows the cardiovascular system to rest and recover overnight. During the day, their bodies handled blood sugar more effectively, suggesting improved insulin function.
Researchers say these changes are important because poor cardiometabolic health is common and can lead to chronic illnesses such as diabetes, fatty liver disease, and heart disease. In recent years, only a small percentage of adults have met the criteria for optimal cardiometabolic health.
Another encouraging finding was that participants were able to stick to the plan. Because the fasting window overlapped with sleep time, it may feel easier than traditional diets that require strict calorie counting.
The researchers plan to test this approach in larger studies, but they believe it could become a simple, drug-free strategy to improve health, especially for people at higher risk of metabolic disease. The message is straightforward: giving your body a longer break from food at night—and finishing dinner earlier—may help your heart and metabolism stay healthier over time.
