[Obesity and type 2 diabetes mellitus (Update 2026)].

Obesity is a chronic disease with a variety of metabolic, mechanical and psychosocial complications, including a high risk of developing prediabetes and subsequently type 2 diabetes mellitus. The choice of antidiabetic treatment as well as concomitant treatment, increasingly takes this into account. Modern glucagon-like peptide 1 (GLP-1) analogues and the combined gastric inhibitory polypeptide (GIP)/GLP‑1 agonist tirzepatide play an important role in the combined treatment of obesity and type 2 diabetes mellitus. Metabolic surgery is currently indicated for people with type 2 diabetes mellitus and a body mass index (BMI) > 30 kg/mand can contribute, at least in part, to diabetes remission but it must be integrated into an appropriate lifelong care plan. Every obesity therapy is always based on lifestyle modifications. Due to the large number of new drugs and the many new studies in which an attempt was made to cite the most relevant ones, major changes were made to this chapter compared to 2023. The indications for metabolic treatment were also adjusted.