A novel, personalized approach to nighttime fasting, synchronized with an individual’s circadian rhythm—a key regulator of cardiovascular and metabolic functions—has been introduced in new Northwestern Medicine research, all without necessitating any changes to overall caloric intake. The findings of this study are featured in the journal Arteriosclerosis, Thrombosis, and Vascular Biology.
The investigation revealed that among midlife and older adults at elevated risk for cardiometabolic conditions, extending the overnight fasting window by approximately two hours, dimming lights, and halting food consumption three hours before bedtime led to improvements in both cardiovascular and metabolic markers, observed both during sleep and wakefulness.
“Aligning the fasting period with the body’s natural sleep-wake cycle can boost the coordination among the heart, metabolism, and sleep, which together offer cardioprotection,” commented study co-author Daniela Grimaldi of Northwestern University Feinberg School of Medicine.
“For timed-eating restrictions to yield physiological benefits, the timing of food intake relative to sleep is as crucial as the quantity and composition of consumed food,” stated the study’s lead author, Phyllis Zee, Director of the Center for Circadian and Sleep Medicine and Chief of Sleep Medicine in the Neurology Department at Feinberg Hospital.
Prior research indicated that in 2017-2018, a mere 6.8% of the U.S. adult population exhibited optimal cardiometabolic health. Poor cardiometabolic status can precipitate chronic ailments, encompassing type 2 diabetes, non-alcoholic fatty liver disease, and cardiovascular disorders.
Time-restricted eating continues to gain traction as studies suggest it can enhance cardiometabolic health and rival traditional calorie-restricted diets; however, much of the existing research focuses on the duration of fasting rather than how fasting aligns with sleep schedules—a pivotal factor in metabolic regulation.
Given the adherence rate of nearly 90% in this particular study, the innovative strategy presented here—using the sleep period as a benchmark for timing time-restricted eating—could emerge as a more accessible, non-pharmacological strategy to boost cardiometabolic health, particularly for middle-aged and older individuals who face heightened risks for cardiometabolic diseases, the authors noted.
The researchers indicated plans to refine the protocol developed in this investigation and implement it in larger, multi-site clinical trials.
Over the 7.5-week study duration, participants who concluded eating at least three hours before sleeping showed significant advantages over those maintaining their usual eating patterns. These benefits included:
Improved overnight cardiovascular metrics (a 3.5% drop in blood pressure and a 5% decrease in heart rate): A more pronounced decline in both readings was observed during sleep, which is a vital indicator of cardiovascular fitness. Notably, their hearts beat faster when they were active during the day, and the rate slowed during nocturnal rest. A greater diurnal rhythm is associated with better cardiovascular status.
Enhanced daytime blood sugar management: Their pancreases responded more effectively to glucose challenges, suggesting an improved capacity to secrete insulin and maintain more stable glucose levels.
The study involved 39 overweight/obese participants (aged 36 to 75 years) who were randomized to either an extended overnight fasting period (13–16 hours of fasting) or a control group (usual fasting duration of 11–13 hours). Both groups practiced light dimming three hours prior to sleep. Women constituted 80% of the intervention group.
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