Ovariectomy diminished the protective effects of female gonadal hormones on the homeostatic model assessment for insulin resistance (HOMA-IR), serum alanine transaminase levels, hepatic steatosis score, and the expression of hepatic genes associated with MASLD progression and IR, such as Fasn, Srebf1, Saa1, Cd36, Col1a1, Pck1, and Ppargc1a. Genistein treatment in gonadectomized mice significantly reduced body weight gain and the hepatic steatosis score in both sexes. This evidence concerns the gene COL1A1 and fatty liver disease.