Effect of time-based energy intake goals on weight loss during obesity treatment. - PROJECT SUMMARY/ABSTRACT Obesity is a complex disease, and innovative treatments that enhance initial and long-term weight loss are needed. One novel treatment approach uses a biobehavioral framework, focusing on time-based energy intake goals (how energy intake is distributed across the day). Time-based dietary goals are believed to promote synchronization of biological and behavioral circadian rhythms, and determining the health benefits of these goals is an objective of NIH’s nutrition strategic plan. Empirical testing of this time-based strategy is limited, and what has been conducted has been short-term (< 3 months) interventions. That said, current findings support that eating more energy earlier in the day and less energy later in the day increases weight loss during obesity treatment. The effect usually starts early in treatment and increases over time, but sustained impact is unexplored. One mechanism for this relationship is enhanced appetite regulation. Within a reduced energy diet, goals that provide a morning-loaded energy distribution result in lower hunger, reduced desire to eat, and/or greater fullness ratings than goals that provide an afternoon/evening-loaded energy distribution. However, the relationship between appetite regulation changes and weight loss has not been examined. Finally, chronotype, an individual’s preferred timing of daily activities thought to reflect circadian rhythms, may moderate the effect of time-based dietary goals. No investigation has examined the influence of chronotype on the relationship between distribution of energy intake and weight loss. To address these gaps, we will test the more longer-term (12 months) effect of time-based energy intake goals on weight loss. We will explore if enhanced appetite regulation is a mediator of the relationship and whether chronotype moderates the effect. For this, 174 adults with overweight or obesity will be randomly assigned to one of three, 12-month lifestyle interventions: 1) Morning (a morning-loaded energy distribution); 2) Evening (an afternoon/evening-loaded energy distribution); or 3) Standard (no guidance on energy distribution). All conditions will receive the same reduced-energy, low-fat dietary prescription, in which the guidance on the eating window length and the number of eating occasions is identical; a physical activity goal; and a cognitive behavioral intervention. Assessments will occur at 0, 3, 6, and 12 months on anthropometrics, diet (24-hr recalls with time-stamped digital images verifying timing of intake, combined with continuous blood glucose monitoring to objectively assess for length of the eating window and number of eating occasions), sleep regularity (actigraphy), appetite regulation as assessed via ecological momentary assessment, and chronotype. We anticipate that Morning will have the greatest percent weight loss, earliest midpoint of energy intake, greatest sleep regularity, and better appetite regulation at 12 months. We will explore if appetite regulation mediates the relationship between time- based energy intake goals and weight loss, and if chronotype moderates examined relationships.
