OBJECTIVES/SPECIFIC AIMS: We hypothesized that increasing percent calories from MUFA (%MUFA) would be associated an increased FFM/FM index. METHODS/STUDY POPULATION: Nine consecutive HFpEF patients with obesity participated in a 12-week pilot feasibility trial of UFA supplementation (NCT03310099). Subjects were educated at baseline by a dietitian on UFA rich foods including high MUFA choices such as extra-virgin olive oil, canola oil and avocados. Participants were given a list of items, corresponding serving sizes and asked to eat at least one serving of these UFA rich foods per day for 12 weeks. Adherence was encouraged through weekly phone calls by the dietitian. Standardized 5-pass 24-hour dietary recall was performed by a dietitian at baseline and 12 weeks. The recalls were analyzed to establish intake of MUFA in percent calories (%kcals) with Nutrition Data Systems for Research software (NDSR). Body composition including FM%, fat free mass percent of body weight (FFM%) and ratio of FFM to FM (FFM/FM Index) was measured with bioelectrical impedance analysis (RJL systems) at baseline and 12 weeks. Statistical analysis was performed with SPSS (24.0). Spearman rank test was used for correlations. Values are expressed as numbers and percentages or as median and interquartile range (IQR). RESULTS/ANTICIPATED RESULTS: Subjects were mostly female (56%) with a median age 56 (IQR 50-59). Baseline median body mass index (kg/m2) was 36.7 (36.2-48.0), median FM% was 44.5 (IQR 32.5-53.4), median FFM% was 55.5 (IQR 46.7-67.5) and median FFM/FM Index was 1.25 (IQR 0.88-2.1).The only significant change was an increase in %MUFA from baseline 12.4% (IQR 6.9-14.3) to 12 weeks 21.8% (17.6-36.9) (p = 0.008). Increased %MUFA was highly associated with increased FFM% (r = 0.783, p = 0.013) (Figure 1A), decreased FM%(r = −0.783, p = 0.013)(Figure 1B) and increased FFM/FM index (r = 0.800, p = 0.010) (Figure 1C). All correlations remained statistically significant after adjustment for changes in energy intake. DISCUSSION/SIGNIFICANCE OF IMPACT: Increasing dietary %MUFA is protective against negative changes in body composition in patients with obesity and HFpEF, independent of changes in caloric intake. Future work should focus on whether the correlation found in this pilot study translate in improved body composition and finally, exercise tolerance and clinical outcomes.