Changes in bone mineral density and bone turnover markers in obese women after short-term weight loss therapy during a 5-year follow-up

INTRODUCTION: The protective effect of adipocity on bone metabolism has not been confirmed during long-term follow-up. It is not known whether the rate of bone turnover and changes in mineral metabolism in obese people result from endocrine properties of the adipose tissue or merely the mechanical load. OBJECTIVES: The aim of the study was to evaluate bone and calcium-phosphorus metabolism in obese women during a 5-year follow-up. PATIENTS AND METHODS: The study involved 47 obese women who underwent a 3-month weight loss therapy. We evaluated changes in the serum levels of parathormone (PTH), calcidiol (25(OH)D3), collagen type I crosslinked C-telopeptide (CTx-I), osteocalcin, total calcium, inorganic phosphates, and in bone mineral density. The control group consisted of 17 healthy women with proper body weight. RESULTS: We observed a similar decrease in bone mineral density (BMD) in the lumbar spine and femoral neck, and a comparable decrease in the serum levels of CTx-I and osteocalcin in both groups during the 5-year follow-up. Changes in serum PTH levels were not statistically significant. In obese women, a nonsignificant increase in the serum level of 25(OH)D3 was observed as early as after a 3-month weight loss therapy and during follow-up. In controls, serum 25(OH)D3 levels tended to decrease. During follow-up, the number of obese patients with disturbances in vitamin D metabolism decreased from 78.7% to 53.2% (P = 0.01). Such disturbances were observed in 35.3% of the control group. In obese patients, there was a positive correlation between the change in body mass and BMD in the proximal femur (r = 0.279, P = 0.04). In controls, there was a positive correlation between the change in body mass and BMD in the lumbar spine (r = 0.477, P = 0.05). CONCLUSIONS: In obese women who underwent weight loss therapy, the levels of bone turnover markers decreased and abnormal vitamin D metabolism was still observed during the 5-year follow-up.