Hepatic FGF21 is not required for fasting metabolism but guides protein appetite post energy depletion. - Bruse J; Marbach C; Polizzi A; Landre T; Salvi J; Alquier-Bacquie V; Chen SP; Huillet M; Rives C; Martin CMP; Perrier P; Benhamed F; et al. (EMBO reports, 2026)