Surgery for weight loss in adults is a major surgical intervention used when other treatments for obesity fail. This review updates a 2003 Cochrane review and assesses the effects of bariatric surgery compared to non-surgical interventions and different surgical procedures. Twenty-two trials involving 1798 participants were included, with follow-up periods ranging from 12 to 10 years. The review found that bariatric surgery leads to greater weight loss and improvement in comorbidities like diabetes compared to non-surgical interventions. Laparoscopic gastric bypass (LRYGB) resulted in greater weight loss and BMI reduction compared to adjustable gastric banding (LAGB) up to five years post-surgery. LRYGB also had higher hospitalization duration and more complications than LAGB. Open RYGB, LRYGB, and laparoscopic sleeve gastrectomy (LSG) all led to weight loss, but no clear superiority was found between them. Biliopancreatic diversion with duodenal switch (BDDS) resulted in greater weight loss than RYGB in morbidly obese patients. LRYGB and LSG had similar outcomes, but this was based on one small trial. Isolated sleeve gastrectomy (LISG) led to better weight loss outcomes than LAGB after three years. Gastric imbrication had no significant difference in weight loss compared to LSG. Adverse events and reoperation rates were generally poorly reported, and long-term effects of surgery remain unclear. The review concludes that surgery results in greater weight loss and improvement in comorbidities compared to non-surgical interventions, with certain procedures like LRYGB and BDDS showing better outcomes. However, the quality of evidence is generally low, and long-term effects are not well understood.Surgery for weight loss in adults is a major surgical intervention used when other treatments for obesity fail. This review updates a 2003 Cochrane review and assesses the effects of bariatric surgery compared to non-surgical interventions and different surgical procedures. Twenty-two trials involving 1798 participants were included, with follow-up periods ranging from 12 to 10 years. The review found that bariatric surgery leads to greater weight loss and improvement in comorbidities like diabetes compared to non-surgical interventions. Laparoscopic gastric bypass (LRYGB) resulted in greater weight loss and BMI reduction compared to adjustable gastric banding (LAGB) up to five years post-surgery. LRYGB also had higher hospitalization duration and more complications than LAGB. Open RYGB, LRYGB, and laparoscopic sleeve gastrectomy (LSG) all led to weight loss, but no clear superiority was found between them. Biliopancreatic diversion with duodenal switch (BDDS) resulted in greater weight loss than RYGB in morbidly obese patients. LRYGB and LSG had similar outcomes, but this was based on one small trial. Isolated sleeve gastrectomy (LISG) led to better weight loss outcomes than LAGB after three years. Gastric imbrication had no significant difference in weight loss compared to LSG. Adverse events and reoperation rates were generally poorly reported, and long-term effects of surgery remain unclear. The review concludes that surgery results in greater weight loss and improvement in comorbidities compared to non-surgical interventions, with certain procedures like LRYGB and BDDS showing better outcomes. However, the quality of evidence is generally low, and long-term effects are not well understood.