Abstract

Bariatric/metabolic surgery is the most effective intervention for achieving substantial and durable weight loss 
in people with obesity and has profound, often rapid, effects on glycemic control in type 2 diabetes (T2D). Beyond 
calorie restriction and weight loss, procedures such as Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy 
(SG), biliopancreatic diversion with duodenal switch (BPD-DS), and one-anastomosis gastric bypass (OAGB) 
remodel entero-insular signaling, bile-acid–FXR/TGR5 pathways, gut–brain–liver circuits, and the 
microbiome. These weight-independent mechanisms amplify insulin sensitivity, enhance β-cell function, and 
promote diabetes remission in a sizable subset of patients. Surgery also improves comorbidities—non-alcoholic 
fatty liver disease, obstructive sleep apnea, hypertension, dyslipidemia—and reduces incident cardiovascular 
events and mortality. However, benefits vary with procedure type, baseline β-cell reserve, diabetes duration, and 
adherence to postoperative nutrition and follow-up. Risks include peri-operative complications, micronutrient 
deficiencies, hypoglycemia, nephrolithiasis, alcohol use disorder, bone loss, and weight regain in a minority; 
careful selection, team-based peri-operative care, and long-term surveillance mitigate these. As potent 
anti-obesity/anti-diabetic pharmacotherapies (e.g., GLP-1 receptor agonists and multi-agonists) expand 
options, surgery retains a unique role when severe obesity, refractory hyperglycemia, or complications 
necessitate rapid, durable metabolic change. This review synthesizes mechanisms of glucose improvement after 
surgery; compares procedures and outcomes; summarizes effects on end organs; details peri-operative 
management; and proposes an integrated, precision framework that aligns surgical choice with phenotypes and 
uses adjunct lifestyle and pharmacotherapy to extend remission while minimizing risks.