Preoperative Body Composition Analysis as a Predictor of Weight Loss Outcomes Following Bariatric Surgery: A Bioelectrical Impedance Study

Background: Bariatric surgery (BS) is an effective intervention for severe obesity, but some patients may experience sub-optimal weight loss. This study investigates the role of preoperative body composition parameters, measured via bioelectrical impedance analysis (BIA), in predicting postoperative weight loss outcomes. Methods: A retrospective analysis was conducted on 102 patients who underwent sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), or one-anastomosis gastric bypass (OAGB) between January 2020 and April 2023. Preoperative body composition metrics, including fat mass (FM), fat-free mass (FFM), body cell mass (BCM), and phase angle (PhA), were correlated with percentages of excess weight loss (%EWL) and total weight loss (%TWL) at 12 months post-surgery. Results: The study found that patients with higher preoperative BCM and PhA showed significantly better weight loss outcomes. Specifically, patients with optimal weight loss had a mean BCM of 35.2 ± 3.5 kg and a PhA of 6.1 ± 0.5, whereas those with sub-optimal outcomes had a mean BCM of 29.8 ± 4.2 kg and a PhA of 4.9 ± 0.6 (p < 0.01 for both). Additionally, higher FM was associated with lower %EWL (r = − 0.40, p < 0.01). Multivariable logistic regression analysis identified BCM (OR 2.1, 95% CI 1.3–3.4) and %FM (OR 0.7, 95% CI 0.5–0.9) as independent predictors of successful weight loss. Conclusions: Preoperative BIA parameters, particularly BCM and %FM, are significantly associated with weight loss outcomes in BS patients. These findings suggest a potential role in guiding pre-surgical patient assessment and tailored care, while acknowledging that this relationship is correlational and not necessarily causal.