Time-Restricted Eating

Time-restricted eating involves confining the eating window to 4 to 10 hours per day and fasting for the remaining hours, during which individuals are not required to monitor food intake. ^[1] Time-restricted eating is one of the most studied forms of intermittent fasting, alongside alternate-day fasting and modified alternate-day fasting. ^[2] An international consensus on fasting terminology discussed time-restricted eating as a distinct approach, standardizing definitions to facilitate communication in research and clinical applications. ^[3]

Time-restricted feeding imposes daily cycles of feeding and fasting without caloric reduction, sustaining robust diurnal rhythms; chronic circadian rhythm disruption increases the risk of metabolic diseases. ^[4] Beneficial metabolic effects of time-restricted eating have been observed independently of weight loss, suggesting an intrinsic effect based on the realignment of feeding with the circadian clock. ^[5] Sustaining a robust feeding-fasting cycle, even without altering nutrition quality or quantity, can prevent or reverse chronic diseases in experimental models, whereas erratic eating patterns disrupt the temporal coordination of metabolism. ^[6] Time-restricted eating lowers fasting insulin and improves insulin sensitivity in individuals with prediabetes and obesity ^[7]. After roughly 12 hours of fasting the body switches from glucose to fat metabolism and upregulates

In a systematic review the overall adherence rate to time-restricted eating was 80%, with a 20% unintentional reduction in caloric intake, and it induced an average weight loss of about 3% together with a loss of fat mass. ^[5] A meta-analysis of meal-timing strategies found statistically significant weight change with time-restricted eating compared with control (-1.37 kg), but the effect sizes were small and of uncertain clinical importance. ^[9] When combined with exercise, time-restricted eating likely reduced body mass by -1.86 kg and fat mass by -1.52 kg compared with a control diet with exercise. ^[10] In a network meta-analysis of intermittent-fasting strategies, alternate day fasting showed a small benefit in body weight reduction over time-restricted eating (-1.69 kg), and time-restricted eating showed no significant benefit over continuous energy restriction for body weight. ^[11]

The popularity of time-restricted eating is most likely due to its simplicity and the fact that it does not require individuals to count calories to lose weight, which may help produce lasting metabolic health improvements. ^[1] A Cochrane review of intermittent fasting for cardiovascular disease prevention, which included time-restricted feeding, found that no included trials reported data on all-cause mortality, cardiovascular mortality, stroke, myocardial infarction or heart failure. ^[12] More rigorous and longer studies are needed to confirm the effects of time-restricted eating, understand their mechanisms and assess their applicability to human health. ^{[5] [9]}