Background: Acute myelogenous leukemia (AML) represents 15%–20% of leukemias in children and approximately 33% in adolescents and young adults (AYA) (1). Obesity has been associated with worse outcome in acute lymphoblastic leukemia in AYA patients (pts). To date, however, the relationship between weight and clinical outcomes in AYA pts diagnosed with AML has not been established. We investigated the impact of body mass index (BMI) along with other prognostic factors on outcomes of AYA AML pts receiving intensive chemotherapy and/or allogeneic stem cell transplant (SCT). Methods: This retrospective chart review included pts 18-39 yrs newly diagnosed with AML between 01/2006-12/2023. All pts received intensive chemotherapy with cytarabine- and anthracycline-based induction followed by consolidation chemotherapy +/- SCT. BMI was calculated using height and weight at AML diagnosis. Pts were classified by BMI into under, normal, overweight, or obese categories. AML risk classification (ELN 2022) and HCT co-morbidity index (HCT-CI) were performed. Outcomes included complete response (CR), CR with incomplete counts (CRi), overall response rates (CR+CRi), event free survival (EFS), and overall survival (OS). Results: Eighty-seven pts (median age 25 yrs, range 18-38) were identified. 44 (51%) were male; 85% were Caucasian. Per ELN 2022, 27 (31%) had favorable, 40 (46%) intermediate, and 20 (23%) adverse risk. Overall response rate to chemotherapy was 92% (CR 80%, CRi 12%). CR rate by ELN was 96%, 72% and 58%, respectively. Median OS for all pts was 788 days and per ELN risk was 1379, 569, and 595 days, respectively. Co-morbidity indices (HCT-CI) ranged from 0-5. Sixty-two percent underwent SCT. 29% relapsed. The percentage of pts alive at 2 and 5 years was 54% and 29%. Pts were categorized by BMI: underweight (BMI < 18.5, 6%), normal weight (NW) (BMI 18.5-24.9) (37%), overweight (OW)(BMI 25-29, 26%), and obese (OB) (BMI > 30, 31%) pts. Overall, there was a trend to improved outcomes in NW vs OW and OB pts. Median OS was 1006 (NW) vs 748 (OW) vs 678 (OB) days (p=0.0036 for NW vs OW/OB). Two-year OS was 63%, 52%, and 48%; 5-year OS was 38%, 26%, and 19%. The impact of BMI was dependent on AML karyotype. In favorable risk AML AYA pts, the relapse rate was 4%, 4% and 12%. Median OS was 1982 (NW), 1169 (OW), and 1256 (OB) days (p=0.0525 NW vs OW/OB). Five-year OS was 50%, 25% and 18%. The most common causes of death were GVHD-induced multi-organ failure and respiratory failure which did not correlate with HCT-CI. In intermediate and adverse risk AML, there was no difference in outcomes by BMI. Conclusions: Outcomes of favorable risk AYA AML pts following intensive chemotherapy +/- SCT was influenced by BMI with increased mortality and shorter OS in pts with high BMI (overweight and obese) as compared to normal BMI. Additional studies to confirm this finding and elucidate the underlying reasons are warranted.