Correlation Between Body Mass Index (BMI) and Postoperative Complications in Elective General Surgery: A Multicenter Study.

BACKGROUND: Body mass index (BMI) is a widely used measure for assessing nutritional status and has been linked to surgical outcomes. Both obesity and underweight status may predispose patients to adverse postoperative events. OBJECTIVE: This study aimed to assess the correlation between BMI and 30-day postoperative complications and to determine the association between BMI categories and the incidence, type, and severity of these complications. METHODS: This cross-sectional multicenter study was conducted at Al-Sheikh Jinnah Memorial Teaching Hospital, Sialkot; Ganga Ram Hospital, Lahore; and Avicenna Hospital, Lahore, from October 2024 to April 2025. A total of 355 adult patients (aged 18-70 years) scheduled for elective general surgical procedures were enrolled using nonprobability consecutive sampling. Preoperative BMI was calculated and categorized according to the WHO classification. Postoperative complications within 30 days were recorded and classified using the Clavien-Dindo grading system. RESULTS: The mean age of the study population was 44.7 ± 13.2 years, with 198 males (55.8%) and 157 females (44.2%). The mean BMI was 27.4 ± 4.9 kg/m², with 7.9% underweight, 34.9% normal weight, 35.5% overweight, and 21.7% obese. Overall, 92 patients (25.9%) developed postoperative complications, with rates highest in obese (36.4%) and underweight (25.0%) groups compared to normal-weight patients (18.5%) (p = 0.003). Surgical site infection was the most common complication (10.7%), followed by pulmonary complications (5.9%) and wound dehiscence (4.2%). Obese patients had significantly longer operative times and hospital stays. CONCLUSION: Extremes of BMI, particularly obesity, are associated with higher rates of postoperative complications in elective general surgery. Preoperative BMI assessment should be integrated into surgical risk stratification, and targeted optimization strategies should be implemented to reduce BMI-related morbidity.