Factors associated with different patterns of weight change after bariatric surgery: A longitudinal study

Background: The mean weight loss (WL) after successful bariatric surgery is approximately one third of the initial body weight, which is mainly achieved between the first 2 years of follow-up. However, 15%–35% of patients do not achieve a significant percentage of total WL (%TWL). Information on factors associated with a higher or lower WL after bariatric surgery is limited. This study aimed to assess the change in %TWL and describe the factors associated with greater or lesser WL over time. Methods: This prospective longitudinal study included patients treated with laparoscopic Roux-en-Y gastric bypass or sleeve gastrectomy. Baseline data were recorded before surgery. Follow-up was performed at 3 (n = 141), 6 (n = 208), 9 (n = 115), 12 (n = 216), 24 (n = 166), and 36 months (n = 99). Generalized estimating equation analysis was performed to assess the changes in %TWL over time and factors associated with different patterns of WL. Results: In total, 231 patients were included (women, 82.2%; basal body mass index (BMI) 41.4 ± 5.1 kg/m²). The tendencies to increase %TWL (32 ± 6.5) were evident in the first year and stabilized thereafter. Sustained nutritionist follow-up (2.3%, p = 0.004), baseline BMI >40 kg/m² (0.4%, p < 0.001), and WL ≥ 10 kg before surgery (0.3%, p = 0.001) were associated with a higher %TWL. Patients who performed physical activity >30 min/day after surgery reduced their %TWL by 0.6% (p = 0.002). Conclusions: Modifiable factors such as nutritional monitoring and WL before surgery are associated with a significant increase in %TWL over time. Basal BMI was associated with a significant decrease in %TWL.