Metabolic surgery is highly effective in obtaining significant and durable weight loss at a low perioperative risk when appropriate patient selection and long-term follow-up are ensured. Observational data suggest that these benefits lead to less adverse CV risk profiles with a consequent reduction in macrovascular events and mortality. Additional benefits may include improved quality of life and a reduced risk for other obesity- and diabetes-related disorders, including microvascular disease, sleep apnea, fatty liver disease, and malignancies.
Recent clinical guidelines have stated that metabolic surgery should be recommended in patients with a BMI ≥40 kg/m2 without concomitant medical problems and in patients with a BMI ≥35 kg/m2 who have at least one severe obesity-associated comorbidity (e.g., poorly controlled T2DM). Comorbidity prevalence in patients with a BMI 35-39.9 kg/m2 is high, approximately 50%, 10%, and 20% for hypertension, diabetes, and dyslipidemia. Metabolic surgery should also be considered in patients with a BMI 30-34.9 kg/m2 and poorly controlled T2DM. Because of the differences in the relationships among BMI, visceral fat, and CV and metabolic risk in patients of Asian descent, it has been suggested that BMI cut-offs be lowered by 2.5 kg/m2 in this population.
Candidates for metabolic surgery should be carefully selected using a multidisciplinary team approach. Patients must have an acceptable operative risk, be motivated to lose weight, and have responded inadequately to behaviorally based treatment. However, optimization of glycemic control should be attempted. Metabolic surgery is contraindicated in patients with current alcohol or substance abuse, uncontrolled psychiatric disorder, poor understanding of the risks and benefits, and lack of commitment to nutritional supplementation and long-term postoperative follow-up. Scoring tools, such as the Individualized Metabolic Surgery Score, may assist in clinical decision making.
In a recent meta-analysis of 11 randomized controlled trials with 796 obese patients, metabolic surgery resulted in a 26 kg greater weight reduction than nonsurgical treatment (p < 0.001). Studies that have reported long-term (>5 years) outcomes include the prospective, matched SOS (Swedish Obese Subjects) study, in which mean weight loss at 15 years was 27% for gastric bypass and 13% for gastric banding compared with 1% for controls. Observational data suggest that the reduction in CV risk factors translates to better patient outcomes.