Improvement of insulin resistance (IR) as contributor of diabetes remission and prevention is a well known beneficial effect of BS. We investigated the changes in IR and sensitivity (IS) in MO patients with newly diagnosed type 2 diabetes (DM) before and 2 years after BS and compared the changes to patients with either impaired fasting glucose or impaired glucose tolerance (IGT/IFG). We included 27 patients with DM (mean age 44±12 years, mean±SD, BMI 49± 10kg/m²) and 104 patients with IGT/IFG (mean age 41±11 years, BMI 47± 7kg/m²). All patients had a 75g oGTT, glucose and insulin levels were repeatedly measured for calculation of IR and IS indices (Table). BMI (p= 0.742) and age (p= 0.194) were not different between both groups. Indices are shown in the Table. Before BS, IR was significantly higher in DM for all indices (p<0.001), except for AUC insulin (p=0.631). After BS, there were no significant differences in AUC glucose (p= 0.454), HOMA (p=0.905) OGIS (p=0.355), Matsuda (p= 0.469) and the oral disposition Index (0.171). IGT/IFG patients had a higher AUC insulin (p= 0.024) and a lower IGI (p= 0.024) compared to DM. Newly diagnosed DM patients are more insulin resistant compared to IGT/IGF. BS reduces IR to the same level in both groups. Post-glucose challenge AUC insulin remained higher in IGT/IFG, indicating better pancreatic insulin secretion reserve, which might translate to better diabetes prevention. Disclosure J. Brix: None. E. Krzizek: None. A. Tura: None. G. Pacini: None. B. Ludvik: Advisory Panel; Self; Amgen Inc., AstraZeneca, Boehringer Ingelheim International GmbH, Sanofi, Takeda Development Centre Europe Ltd. Research Support; Self; Akebia Therapeutics, Eli Lilly and Company, Novartis AG, Novo Nordisk A/S. Speaker's Bureau; Self; Merck Sharp & Dohme Corp.