Body Composition Changes and Factors Influencing the Total Weight Loss Rate After Laparoscopic Sleeve Gastrectomy.

Objectives: While the effectiveness of metabolic/bariatric surgery has been confirmed, understanding the factors associated with weight loss is paramount for providing guidance in postoperative treatment strategies. Here, we aimed to examine the factors associated with long-term maintenance of weight loss after laparoscopic sleeve gastrectomy (LSG). Methods: This prospective observational cohort included patients who underwent LSG at a single academic health center between January 2017 and June 2022. We examined their body composition using InBody 720 or 770 and analyzed the factors associated with the percentage of total weight loss (%TWL) for 24 months. Results: The median body mass index (BMI) was 38.8 (interquartile range [IQR]: 35.6-46.7) preoperatively, 32.7 kg/m² (IQR: 28.2-38.7) at 12 months postoperatively, and 33.9 kg/m² (IQR: 29.1-40.1) at 24 months postoperatively. The lowest BMI was observed at 12 months (p < 0.001 vs. preoperative), followed by a significant increase at 24 months (p = 0.003). However, BMI remained significantly lower at 24 months than preoperatively (p < 0.001). The skeletal muscle mass to fat mass ratio (SMM/FM) was 0.59 (IQR: 0.50-0.71) preoperatively, 0.79 (IQR: 0.58-1.26) at 12 months, and 0.70 (IQR: 0.54-1.05) at 24 months, peaking at 12 months (p < 0.001 vs. preoperative) and decreasing significantly by 24 months (p < 0.001). Nevertheless, the SMM/FM ratio at 24 months remained higher than preoperative values (p < 0.001). Median body weight and %TWL were 86.0 kg and 15.6%, respectively, at 24 months after LSG. The SMM/FM ratio at 12 months was positively correlated with %TWL at 24 months after adjusting for age and sex. Conclusions: The effects of LSG persisted for up to 24 months postoperatively. The SMM/FM ratio 12 months after LSG was associated with the rate of weight loss at 24 months.