LSG: laparoscopic sleeve gastrectomy; LRYGB: laparoscopic Roux-en-Y gastric bypass; RCT: randomized controlled trial; %EWL: percent excess weight loss; SASI: single-anastomosis sleeve ileal; BMI: body mass index; GLP-1 RAs: glucagon-like peptide-1 receptor agonists; AGB: adjustable gastric banding; GERD: gastroesophageal reflux disease; APEX: adjustable gastric banding postmarket approval clinical study; IP: itopride; DP: domperidone; T1DM: type 1 diabetes mellitus; T2DM: type 2 diabetes mellitus; GI: gastrointestinal; ARI: aldose reductase inhibitor. This evidence concerns the gene GCG and diabetes mellitus.