Previous studies have identified a polyunsaturated fatty acid, 15-keto-PGE2, which can reduce muscle inflammation and increase insulin sensitivity, showing potential for muscle growth. We explored the possibility of this fatty acid converting adipose tissue to muscle tissue in mice. After treating obese sarcopenic mice with 15-keto-PGE2, we conducted whole-genome mRNA sequencing and found a significant increase in the expression of muscle-specific genes in the subcutaneous adipose tissue of the mice. Pathway analyzing software GSEA confirmed that this fatty acid strongly stimulates biological pathways in subcutaneous adipose tissue related to muscle differentiation, contraction, and structure. Further experiments with the 3T3-L1 adipocyte precursor cells showed that 15-keto-PGE2 can induce the expression of muscle-specific genes in adipocytes. Finally, we observed that in elderly obese sarcopenic mice treated with 15-keto-PGE2, there was a decrease in body weight, blood glucose, and fat mass, along with an increase in muscle mass and strength, confirming that 15-keto-PGE2 can simultaneously reduce fat and increase muscle mass in vivo.