Overnight fasting aligned with sleep cycle improves heart health

Overnight fasting tied to sleep cycle improves heart health

Extending your overnight fast to align with your natural sleep schedule can improve heart and metabolic health, even without cutting calories. A new Northwestern Medicine study found that middle-aged and older adults at risk for heart disease benefited from a longer fasting window and avoiding food before bed.

The research, published February 12th in the journal Arteriosclerosis, Thrombosis, and Vascular Biology, focused on when participants ate, not what or how much. "Timing our fasting window to work with the body's natural wake-sleep rhythms can improve the coordination between the heart, metabolism and sleep," said first author Dr. Daniela Grimaldi.

Aligning eating with sleep timing is key

Time-restricted eating has become popular for its potential health benefits, but most research has focused on the length of the fast. This study investigated whether aligning that fast with a person's circadian rhythm—the body's internal sleep-wake clock—was crucial.

"It's not only how much and what you eat, but also when you eat relative to sleep that is important," said corresponding author Dr. Phyllis Zee. The goal was a realistic, non-drug approach for older adults, who have a higher risk for conditions like type 2 diabetes and heart disease.

The study had nearly 90% adherence, suggesting this method is practical. The team plans to refine the protocol and test it in larger trials.

Measurable improvements in key health markers

The 7.5-week study involved 39 overweight or obese adults, aged 36 to 75, who were at elevated cardiometabolic risk. Participants were split into two groups:

• An intervention group that extended their overnight fast to 13-16 hours and stopped eating at least three hours before bedtime.
• A control group that maintained their usual eating habits with an 11-13 hour fast.

Both groups dimmed lights three hours before sleep. The intervention group, which was 80% women, saw several significant improvements compared to the control group.

Better blood pressure, heart rate, and blood sugar

Those who adjusted their eating schedule experienced measurable benefits during sleep and the following day. Their nighttime blood pressure decreased by 3.5% and their heart rate dropped by 5%.

These changes reflect a healthier daily rhythm, where heart rate and blood pressure rise with daytime activity and fall appropriately at rest. A stronger day-night rhythm is linked to better cardiovascular health.

Participants also showed improved blood sugar control. Their pancreas responded more effectively to glucose, suggesting better insulin release and steadier blood sugar levels throughout the day.