Poster Abstracts

Background: Australians' demand for metabolic and bariatric surgery is increasing, yet research on when fat-free mass, weight, and resting metabolic rate stabilise post-procedure is contradictory.<br/><br/>Aim: To explore and describe the changes in calculated resting metabolic rate, fat-free mass, and total body weight in patients undergoing metabolic and bariatric surgery over 12-months post-procedure.<br/><br/>Methods: A single-site longitudinal observation study recruited metabolic and bariatric surgery patients from a private clinic between June 2020 and January 2024. Anthropometric measures and body composition (dual energy x-ray absorptiometry) were taken pre-procedure, 6-months, and 12-months post-procedure. Resting metabolic rate was calculated using the Mifflin St. Jeor equation with fat-free mass. Data were analysed in SPSS and paired t-tests were performed between time points.<br/><br/>Results: N = 30 participants (BMI: 41.1 ± 8.0 kg/m2, age 48.5 ± 9.6 years, 93% female) were assessed pre- and 6-months post procedure, n = 22 had additional 12-month measures. Weight changes had not stabilised by 12-months post-procedure (0–6 months: 26.26 ± 9.05 kg, p &lt; 0.001, 6–12 months 5.59 ± 4.77 kg, p &lt; 0.001). Fat-free mass and calculated resting metabolic rate had stabilised by 6-months (5.87 ± 3.47 kg, p &lt; 0.001; 484.0 ± 286.0 kJ/day, p &lt; 0.001), with no significant changes from 6 to 12 months.<br/><br/>Conclusion: In metabolic and bariatric surgery patients, decreases in fat-free mass and calculated resting metabolic rate stabilised by 6-months; however, weight loss continued to 12-months suggesting weight loss between 6- and 12-months is driven by a loss of fat-mass. Future research with shorter follow-up as well as the use of indirect calorimetry may enhance results. Longer-term follow-up may help in long-term management of weight and body composition.