MON-695 Diurnal Rhythm in Meal Responses of Hunger and Appetite in Bariatric Surgery Patients One Year After Vertical Sleeve Gastrectomy

Abstract Disclosure: I.G. Lempesis: None. H. Koh: None. I. Mason: None. R. Knaier: None. P. Medhati: None. A. Cisse: None. C. Kaltsas: None. M. Pikus: None. E.M. Lynch: None. M. Garaulet: None. J. Qian: None. A. Tavakkoli: None. F.A. Scheer: None. Background: Obesity is a significant global public health issue. Sleeve gastrectomy (SG), the most common bariatric surgery, influences neurohormonal pathways controlling appetite and metabolism, resulting in impressive weight loss. However, 25% of patients experience poor weight loss, potentially influenced by differences in post-surgical diurnal rhythms in hunger and appetite, resulting in eating later during the day, a known risk factor for obesity. Aims: We hypothesized that a stronger hunger drive in the evening compared to the morning is associated with less postoperative weight loss 1-year post-SG. Methods: Patients, 1-2 years after bariatric surgery, under highly controlled in-laboratory conditions including a 2-day protocol with fixed sleep/wake cycles and four identical (kcal and composition) and equispaced meals (1, 5, 9, and 13h after scheduled awakening) had detailed assessment of several appetite-related measures, focusing on self-reported hunger, fullness, and nausea, with visual analog scores (VAS) hourly across the 16-h wake episode. The ratios of the 2-h postprandial area under the curve (AUC) for the fourth meal VAS response divided by the first meal VAS response (Ratio 4th /1st meal - capturing maximal contrast of circadian phases of hunger-related measures) were the primary outcomes, and the 16-h AUC was a secondary outcome. Weight loss success was quantified as the percentage of weight loss between the surgery date and 12 months later. Results: 8 participants (mean [SD]; age, 44.8 [10.8] years; 5 female; BMI on day of surgery, 41.6 [8.0] kg/m2, BMI 12 months post-SG. 29.7 [6.4] kg/m2; weight loss: 29.0 [3.8] %; paired T-test, p<0.0001) completed this study and data were analyzed using Pearson’s correlations. A significant negative association was observed only for weight loss % vs. Ratio 4th/1st meal for ”FULL” (r: -0.774, p: 0.03), meaning those feeling relatively fuller in the evening vs. morning lost less weight. The ratios for “HUNGER” (r: 0.50, p: 0.21) and ‘’NAUSEA” (r: 0.77, p: 0.13) weren’t significantly correlated. The 16-h AUCs for the remaining measures were not significantly correlated with weight change % (p>0.05 for all). Conclusion: Our study is novel as it assesses the diurnal appetite-related profiles during standardized timing, size, and composition of meals in a bariatric population for the first time in such a well-controlled manner. Contrary to our hypothesis, we showed that increased self-reported fullness later in the day (fourth vs first meal) was significantly associated with less weight loss. A significant limitation is the small sample size of this exploratory study. Further larger-scale investigations are necessary to assess whether appetite patterns may be associated with SG success and contribute to personalized recommendations. Presentation: Monday, July 14, 2025