Weight Loss-Induced Alterations in Serum Markers of Bone Turnover Persist during Weight Maintenance in Obese Men and Women

Objective: Moderate weight loss alters bone turnover and reduces bone mineral density in overweight men and women. However, it is not known whether bone turnover is normalized during weight maintenance postweight loss. Thus, the objective of the present study was to examine changes in serum bone turnover markers during 9 months of weight maintenance following weight reduction on a very low-energy diet (VLED) in obese men and women. Methods: Thirty-seven men (n = 13) and women (n = 24) aged 50 +/- 9.8 years underwent 3 months of weight reduction on a VLED (similar to 500 kcal/d) followed by 9 months on either a low-carbohydrate or low-fat weight maintenance diet (similar to 1600 kcal/d). Concentrations of osteocalcin (OC) and C-terminal peptide of type I collagen (CTX) in serum were measured using enzyme-linked immunosorbent assay at baseline and at months 3, 6, and 12. Serum parathyroid (PTH) concentrations were measured using a chemiluminescent immunoassay at all 4 time points. Data were analyzed using a 3-factor-repeated measures analysis of variance. Results: Average weight loss was 19% +/- 3% and, during the 9-month weight maintenance period, average weight gain was 3%, with no differences due to diet composition. Serum concentrations of OC and CTX significantly increased after weight reduction and remained elevated during weight maintenance. Serum PTH was reduced after weight loss. Percent changes in OC and CTX were correlated during weight maintenance (r = -0.437, p = 0.008), but not during weight loss. Percent changes in CTX and body weight were negatively correlated during weight loss (r = -0.474, p = 0.003) and maintenance (r = -0.455, p = 0.006). Conclusions: Weight loss induced via a VLED may result in an imbalance between bone formation and resorption and accelerate remodeling. The deleterious effect of energy restriction on bone remodeling rate appears to persist during weight maintenance.