Effects of Bariatric Surgery in Patients With Class I Obesity (BMI 30-35 kg/m2): A Meta-Analysis of Retrospective Studies.

PURPOSE: Over half the global population lives in countries where obesity complications cause higher morbidity than underweight status. Obesity, a global epidemic, carries substantial health, social, and economic consequences. Class I obesity (body mass index [BMI] 30-35 kg/m2) is increasingly prevalent and associated with metabolic comorbidities including type 2 diabetes mellitus (DM) and hypertension (HTN). While bariatric surgery is established for severe obesity, its efficacy in class I obesity remains debated. This meta-analysis evaluated weight loss and comorbidity remission following bariatric surgery in class I obesity. MATERIALS AND METHODS: A systematic search of PubMed, Google Scholar, Cochrane Central, and ScienceDirect identified retrospective studies (2000-2024) reporting weight loss (%excess weight loss [EWL], %total weight loss, BMI) or comorbidity remission (DM, HTN) with ≥12-month follow-up in class I obesity patients undergoing bariatric surgery. Weight loss outcomes were restricted to sleeve gastrectomy (SG) for consistency. Pooled estimates and odds ratios (ORs) used random-effects models. RESULTS: Nine retrospective studies (1,703 patients) met inclusion criteria. All had critical ROBINS-I bias risk. Following SG, pooled %EWL was 90.16% (95% CI, 71.21-109.11) at 12 months and 75.73% (95% CI, 74.66-76.80) at 24 months. Mean BMI fell to 24.70 kg/m2 at 12 months and 25.66 kg/m2 at 24 months. DM remission improved significantly (OR, 0.20; 95% CI, 0.07-0.57 at ≤2 years; OR, 0.15; 95% CI, 0.05-0.49 at >2 years). HTN remission was non-significant (OR, 0.80; 95% CI, 0.38-1.72 at ≤2 years; OR, 0.61; 95% CI, 0.22-1.64 at >2 years). CONCLUSION: SG achieves substantial sustained weight loss in class I obesity with significant diabetes remission. However, critical bias limits evidence certainty. High-quality prospective trials are urgently needed. TRIAL REGISTRATION: PROSPERO Identifier: CRD420261296751.