Preoperative weight loss by noninvasive approach in patients with obesity scheduled for bariatric and metabolic surgery: an update narrative review of indications and results available until 2024.

Metabolic and bariatric surgery (MBS) is the most effective treatment for severe obesity and its metabolic complications. Currently, most MBSs are performed laparoscopically. However, high weight associated with an enlarged liver (especially the left lobe liver section, LLLS) may complicate the technical aspects of this surgery. Therefore, before MBS, moderate preoperative weight loss (PreopWL), and reduction in LLLS are desirable. Moreover, studies are inconclusive regarding which is the best approach to apply. This narrative review aimed to describe the current scientific evidence on the effect of a noninvasive approach, such as dietary or pharmacotherapy or space-occupying devices on PreopWL, peri-operative complications, hospital length of stay, and post-operative complications in patients with obesity scheduled for MBS. We conducted a literature search and screening for relevant publications from January 2010 to June 2024. We found that PreopWL before MBS is helpful for both patients and surgeons, as it leads to various benefits, such as a decrease in body weight and LLLS size, a lower risk of intra- and post-operative complications, shorter surgery times, and reduced hospital stays. In this context, concerning dietary approaches, several dietary protocols have been introduced over time, among which very low-calorie diets and very low energy ketogenic therapy are widely prescribed; however, larger randomized-controlled trials (RCTs) with well-defined dietary protocols are necessary to make definitive conclusions. Obesity management medications, such as the lipase inhibitor orlistat, phentermine/topiramate, naltrexone/bupropion, the glucagon-like peptide-1 receptor agonists (GLP-1RAs) liraglutide and semaglutide, and the novel dual glucose dependent insulinotropic peptide (GIP)/GLP-1 receptor agonist tirzepatide, has shown to be effective in promoting PreopWL before MBS; however, larger, well-designed RCTs are needed to establish optimal treatment protocols and assess their true benefits in patients scheduled for MBS. Space-occupying devices such as the swallowable intragastric balloon and hydrogel capsules, represent a promising tools but further research is essential to confirm their role.