Background: Obese patients are generally believed to be at a higher risk for surgery than those who are not obese, although convincing data are lacking.
Methods: We prospectively investigated a cohort of 6336 patients undergoing general elective surgery at our institution to assess whether obesity affects the outcome of surgery. Exclusion criteria were emergency, vascular, thoracic, and bariatric operations; transplantation procedures; patients under immunosuppression; and operations done under local anaesthesia. Postoperative morbidity was analysed for non-obese and obese patients (body-mass index <30 kg/m(2) vs >or=30 kg/m(2)). Obesity was further stratified into mild obesity (30.0-34.9 kg/m(2)) and severe obesity (>or=35 kg/m(2)). Risk factors were analysed with univariate and multivariate models.
Findings: The cohort consisted of 6336 patients, of whom 808 (13%) were obese, 569 (9%) were mildly obese, and 239 (4%) had severe obesity. The morbidity rates in patients who were obese compared with those who were not were much the same (122 [15.1%] of 808 vs 901 [16.3%] of 5528; p=0.26), with the exception of an increased incidence of wound infections after open surgery in patients who were obese (17 [4%] of 431 vs 92 [3%] of 3555, p=0.03). Incidence of complications did not differ between patients who were mildly obese (91 [16.0%] of 569), severely obese (36 [15.1%] of 239), and non-obese (901 [16.3%] of 5528; p=0.19). In multivariate regression analyses, obesity was not a risk factor for development of postoperative complications. Of note, the additional medical resource use as estimated by a new classification of complications showed no differences between patients who were and were not obese.
Interpretation: Obesity alone is not a risk factor for postoperative complications. The regressive attitude towards general surgery in obese patients is no longer justified.