|IntroductionThe periprostatic adipose tissue (PPAT) is adipose tissue that surrounds the surface of the prostate gland. The PPAT might play a role in the progression of prostate cancer (PCa), as it is made up of fatty acids that could be used by prostate cancer cells. Obesity is associated with poor PCa outcomes and is found to alter PPAT secretions. In this study we sought to identify the fatty acid composition of the peri-prostatic adipose tissue in obese and overweight patients with prostate cancer and understand its relationship with dietary fat intake. Methods PPAT biopsies were collected for fatty acid analysis from 21 participants in the WARRIOR study. The WARRIOR study was a randomized controlled trial that implemented a weight loss intervention in men with PCa. PPAT was examined through flame-ionization gas chromatography and results were compared to known standards to determine fatty acid composition. Mean, standard deviation, and range values for each fatty acid were used to describe the fatty acid content of the PPAT. Information on dietary fatty acid intake was collected through 24-hour recalls at two time points: baseline, and pre-surgery. Diet information was analyzed using the Nutrition Data System for Research (NDSR) database. Dietary fatty acid intake was compared to fatty acid content of the PPAT using Spearman’s correlation coefficient values. Differences in the diet and the fatty acid content of the PPAT between the intervention and the non-intervention group were also analyzed. Results Adequate PPAT for fatty acid analysis was collected from 21 patients. Twenty-seven types of fatty acids were found in the PPAT. Oleic acid, palmitic acid, linoleic acid, stearic acid, myristic acid, and palmitoleic acid were found in high concentrations in the PPAT. Dietary intake of oleic acid, linoleic acid, and palmitic acid were higher than other dietary fatty acids. Other than a few exceptions, dietary intake of most fatty acids do not clearly correlate to fatty acid content of the PPAT . At baseline gadoleic acid (rs = 0.427), oleic acid (rs = 0.399), behenic acid (rs = -0.442), and margaric acid (rs = -0.362) intake correlated to the amount in the PPAT. At the pre-surgery timepoint, behenic acid (rs = -0.402) and palmitoleic acid (rs = -0.376) intake correlated to the amount in the PPAT. Conclusion The distribution of fatty acids in the PPAT seemed to follow a pattern with high amounts of oleic acid, palmitic acid, linoleic acid, stearic acid, myristic acid, and palmitoleic acid, and small concentrations of other fatty acids present. The relationship between dietary fatty acid intake andthe. composition of fatty acids in the PPAT seems to be unclear. Some fatty acids were found to have a fair correlation between diet and PPAT. Future research is required to better understand the relationship between diet and PPAT.