Impact of diurnal versus nocturnal time-restricted eating on cardiometabolic health and circadian rhythm in healthy adults: A protocol for systematic review and meta-analysis.

This article presents a systematic review and meta-analysis protocol aimed at comparing the effects of diurnal versus nocturnal time-restricted eating (TRE) on cardiometabolic health and circadian rhythm in healthy adults. Diurnal TRE typically restricts food intake to an 8–12 hour window during daytime, aligning with the body's natural circadian rhythm, while nocturnal TRE, exemplified by Ramadan fasting, shifts eating to nighttime hours and may disrupt circadian alignment. The review will include randomized controlled trials and observational studies published since 2012, focusing on outcomes such as blood pressure, lipid profiles, glucose metabolism, body composition, and circadian markers like melatonin and cortisol. Preliminary evidence suggests diurnal TRE improves body composition and some cardiometabolic parameters, whereas Ramadan fasting leads to temporary weight loss and mixed effects on metabolic health, with potential circadian disruption due to altered meal timing and sleep patterns. The study acknowledges methodological challenges due to differences in study designs and populations but aims to provide evidence-based insights to inform dietary recommendations and optimize meal timing for cardiometabolic and circadian health.