Bedtime habit: stop eating three hours before bed may support heart health.

A Northwestern study reported that avoiding food within three hours of bedtime improved heart-rate regulation and glucose measures in a small trial of obese adults, and biohacker Bryan Johnson highlighted the finding.

Bryan Johnson shared a new Northwestern University study that looked at when people stop eating before sleep and how that timing relates to heart and metabolic measures. The research tested an extended overnight fasting window versus a shorter fasting window in adults with obesity over 7.5 weeks. Johnson noted he typically fasts for longer but suggested a three-hour pre-bed limit could benefit many people. The study was published in Arteriosclerosis, Thrombosis, and Vascular Biology. Key findings: - The trial enrolled 39 obese adults ages 36 to 75; 21 followed a 13–16 hour overnight fast and 18 followed an 11–13 hour fast for 7.5 weeks. - The extended fasting group averaged 14 hours 51 minutes of fasting and maintained about a 4-hour 24-minute fast before bedtime, versus 11 hours 50 minutes and 2 hours 41 minutes in controls; adherence in the extended group was reported at 88%. - Nighttime heart rate fell by about 2.3 beats per minute in the extended fast group, and heart-rate dipping during sleep improved by nearly 5% compared with controls. - Nighttime diastolic blood pressure decreased (by about 1.8 mmHg) and diastolic dipping increased by 3.5% in the longer fasting group; about 60% of non-dippers converted to dipper status versus 25% in controls. - Nighttime cortisol levels fell and measures of glucose handling improved (mean glucose fell and early insulin secretion improved) in the extended fasting group, while BMI and waist circumference did not change significantly. Summary: The trial found that aligning the fasting window with the sleep cycle—specifically avoiding food within about three hours of bedtime—was associated with improvements in heart-rate regulation, overnight blood pressure patterns, nighttime cortisol and glucose handling without changes in weight measures. Undetermined at this time.