Sleep-aligned Extended Overnight Fasting Improves Nighttime and Daytime Cardiometabolic Function

Background: Time-restricted eating (TRE) has gained attention for its potential cardiometabolic health benefits. Existing TRE approaches may have limited adherence and sustainability due to fixed fasting windows with prolonged fasting duration before sleep, or they involve self-selected fasting windows without specifying the duration relative to sleep, a critical period for cardiometabolic regulation. We hypothesized that an individualized approach that extended overnight fasting (EOF) duration by three hours in alignment with habitual sleep time (last meal ≥3 hours before sleep) would enhance nighttime autonomic balance, decrease blood pressure (BP) and heart rate (HR), increase BP/HR dipping, and glucose regulation compared to a control group maintaining habitual eating patterns. Methods: In this randomized parallel-arm controlled trial, 39 overweight/obese participants (36 – 75 years) completed either an EOF intervention (13h - 16h fasting) or a control condition (habitual fast of 11h - 13h). Both groups dimmed lights 3 hours before bedtime. The intervention duration was 7.5 weeks. Results: Compared to control, EOF intervention significantly improved the co-primary outcome of nighttime dipping of diastolic BP, but not the Matsuda Index of insulin sensitivity. EOF improved secondary measures of nighttime autonomic function and morning oral glucose tolerance, including lower nighttime HR, higher heart rate variability, lower nighttime cortisol and during the oral glucose tolerance test lower glucose level, and higher 30-minute insulinogenic index, indicating improved acute insulin response. Conclusions: Extending overnight fasting duration by three hours in alignment with sleep improved cardiometabolic health in middle-aged/older adults by strengthening coordination between circadian- and sleep-regulated autonomic and metabolic activity. This sleep-aligned TRE approach represents a novel, accessible lifestyle intervention with promising potential for improving cardiometabolic function.