Abstract Background The prevalence of obesity and severe obesity has increased in the general population of modern societies during the last decades with growing implications on health systems. Aim of the present study was to analyse prevalence rates of severe obesity (body mass index (BMI)≥40 kg/m²) in patients with ST-elevation myocardial infarctions (STEMI) between 2006 and 2022 and its association to age, other cardiovascular risk factors and in-hospital- and long-term-outcome rates. Methods All patients admitted with STEMI between 2006 and March 2022 to a large German PCI center entered analysis. Patients were assigned to the study group with severe obesity (BMI≥40 kg/m²), a control group with obesity grade 2 (BMI 35-39.9 kg/m²) and a second control group (BMI <35 kg/m²). Results From a total of 11740 patient included, 269 patients (2.3%) presented with severe obesity with a mean weight of 128.9±18 kg, while 589 patients (5.0%) had obesity grade 2. Patients with severe obesity were on average 6.4 years younger compared to patients with a BMI<35 kg/m²: 57.7±11.5 yrs. vs. 64.1±13.1, p<0.01. Rates of severe obesity were higher in women in most age strata, especially in patients<45 yrs. of age: women 9.3%, men 3.0%, p<0.01. Over time, the proportion of severe obesity increased from 1.9% in 2006-2013 to 2.9% in 2014-2022, p<0.01. This increase was more pronounced in women 2.5 % to 3.9% (p=0.02) compared to men: 1.7% to 2.5% (p<0.01) and most prominent in the young (<45 yrs.): 2.3% to 6.2%, p<0.01. The increase over time could be confirmed in multivariate model for younger men and women, while it failed to reach statistical significance in patients ≥ 55 years of age (table). While there was no association between severe obesity and hyperlipidemia (LDL-cholesterol 120.9±44 mg/dl vs. 121.5±57 mg/dl in controls, p=0.91), it was associated with higher rates of diabetes mellitus (45.5% vs. 18.8%, p<0.01). Patients with severe obesity showed similar rates of multivessel disease (61.6% vs. 63.5%, p=0.51) and successful primary percutaneous coronary interventions (TIMI 2/3 post PCI: 96.2% vs. 95.1%, p=0.44). In a multivariate analysis of outcome severe obesity was associated with similar in-hospital-mortality-rates (OR 0.98, 95% CI 0.6-1.6, p=0.94), however in long term follow-up a trend for a higher 1-year-mortality (OR 1.49, 95% CI 0.98-2.2, p=0.065) and a significantly higher 5-year-mortality (OR 1.82, 95% CI 1.17-1.82, p<0.01) could be observed. Conclusions These results from a large registry study reveal that during the last 16 years rates of severe obesity increased by more than 50% in STEMI-patients. The increase was most prominent in the young and in women, were rates more than doubled. At the same time, severe obesity was associated with a young age during the index event and a worse long-term-outcome.Changes in obesity 2014-22 vs. 2006-13