Relationships between serum leptin and bone markers during stable weight, weight reduction and weight regain in male and female judoists.

OBJECTIVE

Despite a preliminary understanding of leptin-skeletal interactions, data in humans are inconsistent and the exact roles of leptin on bone metabolism have not yet been defined. The aim of this study was to examine the possible role of leptin in the regulation of bone metabolism in healthy, physically trained adults.

METHODS AND DESIGN

Body composition and bone mass (dual-energy X-ray absorptiometry), anthropometry, serum leptin, insulin, cortisol, osteocalcin, C-terminal telopeptide of type I collagen (CTx) and total plasma proteins were measured in judoists at normal body weight, after weight reduction and after weight regain. Physical training, weight cycling history, menstrual status and nutritional intake using a 7-day food record were assessed.

RESULTS

Precompetitive weight loss averaged 4 +/- 0.3% of bodyweight and resulted in a significant decrease in leptin levels of 64% (P < 0.001) and of 31% for insulin (P < 0.0001). CTx and cortisol concentrations rose by 33% (P < 0.0001) and 81% (P < 0.05) respectively. Osteocalcin and total plasma protein remained unaffected by weight loss. A 4 +/- 0.5% weight regain induced a 276% increase in leptin levels (P < 0.001) and an 18% increase in insulin (P < 0.001). CTx and cortisol decreased by 23% (P < 0.0001) and 27% (P < 0.05) respectively. Changes in leptin were significantly correlated with changes in bone resorption marker in response to both weight loss (r = 0.56, P < 0.01) and regain (r = 0.44, P < 0.05).

CONCLUSIONS

These findings suggest that leptin is involved in the regulation of bone metabolism in healthy adults and might play a potential role in the prevention of osteoporosis.