0002 Impact of Acute, Isocaloric Time-Restricted Eating on Resting Metabolic Rate and Obesogenic Factors in Healthy Lean Adults

Abstract

Abstract Introduction Time-restricted eating (TRE) is a dietary strategy in which energy is consumed over a 6-10h window during the day and is associated with reduced energy intake and subsequent weight loss in people with obesity. However, the impact of isocaloric TRE on obesogenic factors such as hormones related to hunger and appetite, as well as energy expenditure and metabolic rate is relatively unknown. We therefore investigated the impact of 1 week of isocaloric TRE on obesity-related outcomes including circulating leptin, ghrelin, and peptide YY (PYY) and resting metabolic rate (RMR). Methods Thirteen healthy adults (8F, 26.9±3.9y, 23.3±2.1kg/m2) participated in a 2-week protocol. During Week 1, energy was consumed over a 13h period with meals individually anchored to habitual wake time and consumed at +1h, +6h, +11h and +14h after wake. For Week 2, participants were instructed to match energy intake from Week 1 but restrict intake to an 8h period (meals at +1h, +5h, and +9h after wake). At the end of each week, participants were admitted to the laboratory for an overnight stay. Blood samples were collected hourly overnight and assayed for leptin, ghrelin, and PYY. RMR was assessed using hood calorimetry immediately after wake. Results TRE was associated with a significant reduction in circulating leptin levels (p< 0.001) without changes in body weight (p=0.536), PYY or ghrelin levels. The respiratory exchange ratio (RER) calculated from hood calorimetry was significantly lower during TRE (0.76 vs 0.81; p=0.04) despite no change in energy expenditure (p=0.478) suggesting a higher reliance on fat oxidation during TRE compared with habitual eating. Conclusion Reductions in leptin in conjunction with lower RER suggests that TRE promotes increased fat utilization as compared with habitual eating. Future studies should evaluate whether long-term isocaloric TRE is associated with reduced adipose tissue mass. Support (if any) This project was supported by R01DK125653.