Researchers at Northwestern Medicine explored whether timing an overnight fast to match a person’s natural sleep wake cycle could improve heart and metabolic health. The circadian rhythm plays a central role in regulating cardiovascular and metabolic function. Importantly, participants did not reduce calories. The focus was entirely on adjusting when they ate.
The study found that middle age and older adults at elevated risk for cardiometabolic disease benefited from extending their overnight fasting window by roughly two hours. They also avoided food and dimmed lights for three hours before going to sleep. These changes led to measurable improvements in heart and metabolic markers during sleep and throughout the following day.
“Timing our fasting window to work with the body’s natural wake-sleep rhythms can improve the coordination between the heart, metabolism and sleep, all of which work together to protect cardiovascular health,” said first author Dr. Daniela Grimaldi, research associate professor of neurology in the division of sleep medicine at Northwestern University Feinberg School of Medicine.
The findings were published Feb. 12 in Arteriosclerosis, Thrombosis, and Vascular Biology, a journal of the American Heart Association.
“It’s not only how much and what you eat, but also when you eat relative to sleep that is important for the physiological benefits of time-restricted eating,” said corresponding author Dr. Phyllis Zee, director of the Center for Circadian and Sleep Medicine and chief of sleep medicine in the department of neurology at Feinberg.
Why Cardiometabolic Health Matters
Earlier data show that only 6.8% of U.S. adults had optimal cardiometabolic health in 2017 to 2018. Poor cardiometabolic health raises the risk of chronic conditions such as type 2 diabetes, non-alcoholic fatty liver disease, and cardiovascular disease.
Time-restricted eating has grown in popularity because studies suggest it can improve cardiometabolic markers and sometimes match the benefits of traditional calorie restricted diets. However, most research has concentrated on how long people fast rather than how well that fasting window aligns with sleep timing, which is crucial for metabolic regulation.
With nearly 90% adherence in this trial, the researchers believe anchoring time-restricted eating to the sleep period may be a realistic and accessible non-pharmacological approach, especially for middle age and older adults who face higher cardiometabolic risk.
The team plans to refine this protocol and expand testing in larger multi-center trials.
Blood Pressure, Heart Rate, and Blood Sugar Improvements
The 7.5 week study compared individuals who stopped eating at least three hours before bedtime with those who maintained their usual eating habits. Those who adjusted their timing experienced several meaningful changes.
Nighttime blood pressure decreased by 3.5%, and heart rate dropped by 5%. These shifts reflected a healthier daily pattern, with heart rate and blood pressure rising during daytime activity and falling at night during rest. A stronger day night rhythm is associated with better cardiovascular health.
Participants also demonstrated improved daytime blood sugar control. When given glucose, their pancreas responded more effectively, suggesting improved insulin release and steadier blood sugar levels.
The trial included 39 overweight/obese adults (36 to 75 years old). Participants were assigned either to an extended overnight fasting group (13 to 16 hours of fasting) or to a control group that maintained a habitual fasting window (11 to 13 hours). Both groups dimmed lights three hours before bedtime. The intervention group consisted of 80% women.
Funding: NIH/National Heart, Lung and Blood Institute, National Institute on Aging, NIH/National Center for Advancing Translational Sciences (NCATS)
