Time-Restricted Feeding, Circadian Rhythms, and CVD

Intermittent fasting strategies, including time-restricted feeding^* interventions, have a range of health benefits, including the improvement of precursors to cardiovascular disease such as obesity, hypertension, dyslipidemia, and diabetes.^1,2 Studies suggest that intermittent fasting treatments may improve health through multiple pathways, potentially reducing oxidative stress,² enhancing mitochondrial health and DNA repair,¹ and triggering autophagy,¹ a cellular recycling system with a possible therapeutic role in some inflammatory diseases.³ And specific timing patterns of feeding and fasting windows may lead to greater improvement of cardiometabolic markers.⁴

Time-restricted feeding is a dietary pattern that optimizes circadian elements such as daily rhythms for insulin peaks and glucose tolerance⁵ by consuming food and beverages within a shortened window of time during the day, extending a person’s nightly fast to 12 hours or more. While there are limited large trials establishing an association between intermittent fasting interventions and improved cardiovascular disease outcomes, the available research suggests that in addition to reducing cardiovascular disease risk factors in healthy populations,^2,4,6 time-restricted feeding may also hold promise as a beneficial adjunctive therapy, improving cardiometabolic health for some patients with metabolic syndrome.⁷

Early time-restricted feeding

The circadian rhythms of the body influence sleep-wake cycles, eating and digestion patterns, and biochemical and metabolic processes.⁸ Studies suggest that interruptions to these biological rhythms and erratic eating patterns may lead to an elevated risk for chronic conditions, including cardiovascular diseases.^8-10 For example, consuming more calories at breakfast may yield better health outcomes,¹¹ while late-night meals may contribute to cardiovascular disease precursors such as obesity.¹²

Time-restricted feeding approaches consider these circadian elements, and in 2018, a small randomized controlled trial (RCT) with pre-diabetic participants was reportedly the first trial to investigate the impact of what researchers termed “early time-restricted feeding.”¹³ This intervention involved a six-hour eating period, no caloric restrictions, and dinner consumed before 3 pm. The control group followed a 12-hour eating window, and after a five-week intervention, compared to controls, the treatment group had reduced insulin levels and blood pressure without any reported weight loss. In addition, the treatment group showed improved insulin sensitivity and beta cell responsiveness.¹³

Additional small clinical trials published in 2019 also investigated the cardiometabolic and other biological impacts of early time-restricted feeding.^14-16 Two of those studies also included a six-hour feeding window of 8 am to 2 pm. Compared to the 12-hour control feeding schedules, results indicated that the early time-restricted feeding treatments: