In a cohort study, only levels of OPA1 (OPA1 mitochondrial dynamin‐like GTPase), a gene essential for inner mitochondrial membrane fusion and cristae remodeling (Giacomello et al, 2020), correlate with muscle mass, and its inducible deletion in the adult mouse triggers FOXO3‐dependent sarcopenia and FGF21 (fibroblast growth factor 21)‐induced systemic aging (Tezze et al, 2017). This evidence concerns the gene FGF21 and sarcopenia.