Abstract Disclosure: F. Plessow: None. M. Wronski: None. M. Rogers: None. M.G. Turley: None. E.R. Golden: None. M. Slattery: None. J.J. Thomas: None. E.A. Lawson: None. M. Misra: None. K.T. Eddy: None. Background: Low estrogen levels and oligomenorrhea are common characteristics in females with a low-weight eating disorder (LWED). In animal models, estrogen status is associated with neural activity in dopaminergic reward pathways affecting reward processing and decision-making. Whether a similar link exists in humans is unknown but important to understand, as reduced reward-driven behavior and an increased delay of gratification driving decision-making hinder recovery from a LWED. To fill this knowledge gap, we studied the relationship between lifetime duration of amenorrhea and hedonic eating and monetary decision-making in a group of females with a LWED. We hypothesized that longer lifetime duration of amenorrhea is associated with reduced hedonic food intake and a smaller delay discounting rate (indicating an increased delay of gratification) in females with a LWED (independent of age and illness severity). Methods: Fifty-six females with a LWED (mean age±SD: 19.84±2.98 years, range: 13.6-23.5 years) and 34 female healthy controls (HC; 19.08±2.41 years, 13.4-22.2 years) underwent a menstrual history to determine the number of missed menses since menarche, Eating Disorder Examination (EDE) to assess ED psychopathology, anthropometric measurements to calculate body mass index (BMI), Cookie Taste Test as a laboratory-based assessment of reward-related eating beyond satiety, and a monetary Delay Discounting Task to determine their delay discounting rate. Between-group differences were tested using Mann-Whitney U-tests, and associations between duration of amenorrhea and caloric intake at the Cookie Taste Test and delay discounting rate in the LWED group were examined using partial Spearman correlations adjusted for age and BMI as a marker for illness severity. Results: By study design, females with a LWED had a lower BMI (17.97±2.16 vs. 21.71±2.57 kg/m2, U=1,802.50, p<0.001, r=0.75) and more pronounced ED psychopathology (EDE Global Score: 2.38±2.50 vs. 0.00±0.00, U=22.50, p<0.001, r=0.83) than HC. They had missed 16.50±22.64 menses since menarche. When controlling for age and BMI, longer lifetime duration of amenorrhea was correlated with lower caloric intake in the Cookie Taste Test (rs=-0.34, p=0.011) and a smaller delay discounting rate indicating an increased delay of gratification (rs=-0.40, p=0.004). Conclusions: This is the first demonstration that lifetime duration of amenorrhea is associated with hedonic food intake and monetary decision-making in females with a LWED, pointing towards a potential role of cumulative estrogen status in reward processing and decision-making in this population. Future research avenues include investigating whether estrogen replacement can increase reward responsiveness and reduce delay of gratification to promote a faster recovery from a LWED. Presentation: 6/1/2024