Long-Term Weight Loss Outcomes Following Sleeve Gastrectomy and Their Association with Diet Quality, Postoperative Complications, and Sociodemographic Factors: A Retrospective Cohort Study in Jeddah, Saudi Arabia

Background/Objectives: Bariatric surgery is an effective intervention for severe obesity; however, long-term outcomes may be influenced by postoperative dietary behaviors, nutritional status, and complications. In Saudi Arabia, longitudinal evidence on weight trajectories and postoperative diet quality remains limited. The present study aimed at evaluating three-year weight status trends; assessing sociodemographic factors, baseline BMI, and postoperative diet quality; and examining nutrition-related complications following bariatric surgery. Methods: This retrospective longitudinal study included 189 adults who underwent sleeve gastrectomy at two tertiary hospitals in Jeddah, Saudi Arabia. Anthropometric data were obtained from medical records at six time points: preoperative, two weeks, six months, one year, two years, and three years postoperatively. Diet quality and postoperative complications were assessed via structured telephone interviews. Weight outcomes were expressed as percentage of total body weight loss (%TBWL), excess body weight loss (%EWL), excess body mass index loss (%EBMIL), and weight regain. Statistical analyses included Friedman’s test, Mann–Whitney U test, and multiple linear regression. Results: Significant improvements in all weight loss indicators were observed over three years (p < 0.001). Diet quality score was the only significant variable associated with weight loss at three years, with higher scores associated with greater %EWL and %EBMIL. Baseline BMI and DQS were significantly associated with %EWL (Beta = −0.17, 95% CI: −1.72 to −0.13 and Beta = 0.21, 95% CI: 1.37 to 7.12, respectively) and %EBMIL (Beta = −0.15, 95% CI: −1.68 to −0.07 and Beta = 0.24, 95% CI: 1.90 to 7.66, respectively). Age was significantly associated with weight regain (Beta = 0.20, 95% CI: 0.02 to 1.08). Conclusions: Bariatric surgery resulted in sustained weight reduction over three years. Postoperative baseline BMI and diet quality were significantly associated with %EWL and %EBMIL, underscoring the importance of structured nutritional follow-up and counseling.