Perspective: Time-Restricted Eating-Integrating the What with the When

Statement of Significance: Time-restricted eating (TRE) is a dietary strategy that focuses on the timing of meals, but frequently neglects the quality and quantity of food consumed. This Perspective challenges researchers in the field of TRE to incorporate rigorous dietary assessment to unravel the complex relations between the type of food consumed and the timing of meals. Time-restricted eating (TRE) is a popular dietary strategy that emphasizes the timing of meals in alignment with diurnal circadian rhythms, permitting ad libitum energy intake during a restricted (similar to 8-10 h) eating window each day. Unlike energy-restricted diets or intermittent fasting interventions that focus on weight loss, many of the health-related benefits of TRE are independent of reductions in body weight. However, TRE research to date has largely ignored what food is consumed (i.e., macronutrient composition and energy density), overlooking a plethora of past epidemiological and interventional dietary research. To determine some of the potential mechanisms underpinning the benefits of TRE on metabolic health, future studies need to increase the rigor of dietary data collected, assessed, and reported to ensure a consistent and standardized approach in TRE research. This Perspective article provides an overview of studies investigating TRE interventions in humans and considers dietary intake (both what and when food is eaten) and their impact on selected health outcomes (i.e., weight loss, glycemic control). Integrating existing dietary knowledge about what food is eaten with our recent understanding on when food should be consumed is essential to optimize the impact of dietary strategies aimed at improving metabolic health outcomes.