Osteocalcin (OC) and the undercarboxylated form (ucOC) are bone-derived peptide hormones produced by osteoblasts that are involved in systemic metabolism and skeletal muscle mass regulation. Human studies have been equivocal regarding the relationship of circulating OC with muscle mass. Our aim was to summarize the published findings on the relationship between OC levels and muscle mass measurements in humans and determine if factors such as age and sex impact the outcome.

PubMed, Scopus, and CINHAL databases were systematically searched to identify empirical human studies reporting the correlation coefficients between OC levels and measures of muscle mass. Muscle mass measurements included total body lean mass (tLM), percent lean mass (%LM), appendicular lean mass (aLM), and lean muscle index (LMI). Studies were included in the meta-analysis, with effect sizes being extracted for total OC (tOC) and ucOC. Subgroup analyses examined age, sex, and health status.

Muscle mass quantified by %LM had a significant correlation with tOC and ucOC. LMI had a significant correlation with ucOC, but not tLM, and aLM. There was a weak, significant positive association between tOC and ucOC with all combined muscle mass measurements, and the relationship with tOC was more evident in male adults.

Circulating OC, specifically ucOC, had a significant relationship with %LM, but not tLM or aLM. Circulating OC appears to be more closely associated with body composition than with total mass. Further studies are needed to determine how age and sex interact with OC regulation of body composition.