The authors reply: Letter on: "Pitfalls in the measurement of muscle mass: a need for a reference standard" by Clark et al. - Buckinx F; Landi F; Cesari M; Fieding RA; Visser M; Engelke K; Maggi S; Dennison E; Al-Daghri NM; Allepaerts S; Bauer J; Bautmans I; et al. (Journal of cachexia, sarcopenia and muscle, 2018)