Insulin-like growth factor-1 (IGF-1) is an anabolic peptide associated with skeletal muscle hypertrophy and regeneration. The concentration of IGF-1 in circulation and in tissues is strongly influenced by nutritional state, including Zn status. It is speculated that tenuous Zn status during recovery from protein-energy malnutrition (PEM) results in decreased IGF-1 concentrations, which leads to incomplete recovery of skeletal muscle mass. Since it would be difficult to explore this speculation in a single study, the hypothesis of this study is that full recovery of muscle fiber diameter following Zn, protein and energy deficiencies is dependent upon the full recovery of serum IGF-1 concentration and Zn status. The objective of the present study was twofold. Firstly, to explore the effect of Zn, protein and energy deficiencies on skeletal muscle mass and fiber diameter in relation to serum IGF-1 concentration in growing rats. Secondly, to investigate the effects of a 30 ppm Zn diet on the recovery of muscle mass, muscle fiber diameter and serum IGF-1 concentration. (Abstract shortened by UMI.)