The SMART study is a 96-week, multicenter, randomized, double-blind, placebo-controlled superiority clinical trial. A total of 256 severe obesity patients are randomized 1:1 to either receive the bariatric surgery plus GCG/GLP-1 dual receptor agonist group (receiving sleeve gastrectomy followed by subcutaneous injections of mazdutide weekly, with stepwise dose escalation to a maintenance dose per protocol) or the bariatric surgery plus placebo group (receiving matched procedure plus placebo injections). The primary objective is to evaluate the potential enhancing weight reduction effects of the combination therapy with bariatric surgery and mazdutide measured by the percentage change of excess weight loss.