Skeletal muscle-specific deletion of FoxO1, FoxO3, and FoxO4 transcription factors in mice dramatically worsened fatty liver disease during prolonged fasting, despite preventing muscle wasting. FoxO-deficient muscle showed impaired fatty acid oxidation and abnormal glycogen buildup, with reduced triglyceride lipase activity. Conversely, muscle-specific FOXO1 overexpression protected against Western diet-induced liver dysfunction. This discovery fundamentally reframes our understanding of fatty liver disease by revealing skeletal muscle as an active metabolic guardian of liver health, not merely a passive tissue that wastes during starvation. The muscle-liver metabolic axis appears more integrated than previously recognized, with muscle FoxO signaling serving as a critical regulatory hub. For the growing population facing metabolic dysfunction-associated fatty liver disease—affecting up to one-third globally—this suggests muscle-targeted interventions could complement traditional liver-focused therapies. The finding that preserving muscle mass alone isn't sufficient without functional FoxO signaling challenges current nutritional strategies during caloric restriction. While conducted in mice, this work opens promising avenues for investigating whether exercise, fasting protocols, or targeted muscle therapies might prevent or reverse fatty liver through FoxO pathway activation.