Time-Restricted Eating, Cardiometabolic Health in Obesity and The Optimal Length of the Eating Window

This narrative review aims to evaluate how the duration of eating windows influences the cardiometabolic effects of Time-Restricted Eating (TRE) protocols among individuals with obesity. In the context of the global obesity epidemic, TRE has emerged as a promising dietary approach, alternative to conventional energy restriction, capable of improving cardiometabolic health by aligning food intake with circadian rhythms. However, due to the heterogeneity across TRE protocols, the impact of eating windows length on these outcomes remains uncertain. Therefore, this review comprehensively analyzes clinical trials assessing cardiometabolic responses across various durations of eating windows to identify which protocol may provide the greatest benefits. Short eating windows (4–6 h), although associated with promising metabolic outcomes, often exhibit poor adherence due to increased hunger, fatigue and social constraints, limiting their long-term viability. Moderate eating windows (8–10 h) appear to offer the optimal balance between metabolic benefits, minimal adverse effects and adherence. Long eating windows (12–14 h), despite higher adherence, provide limited metabolic outcomes and are frequently associated with circadian misalignment, potentially increasing the risk of obesity and related metabolic disorders. All the data mentioned were obtained from clinical trials. TRE has evolved as a promising strategy to enhance cardiometabolic health, especially in individuals with obesity. Eating windows of 8-10h appear to represent the most sustainable TRE protocol, balancing metabolic efficacy with adherence. Nevertheless, further well-designed, long-term randomized controlled trials incorporating chrononutritional assessments are required to establish the optimal eating window for maximizing health outcomes in obesity.