Bone Metabolism in Adolescents and Adults Undergoing Roux-En-Y Gastric Bypass: a Comparative Study

To compare the bone metabolism of adolescents and adults with obesity before undergoing a Roux-en-Y gastric bypass (RYGB) and 6 and 12 months after the surgery.

Adolescents (G1) and adults (G2) with obesity assessed before (T0), six (T1), and 12 months after (T2) RYGB. Sun exposure, serum concentrations of 25(OH)D, calcium, phosphorous, magnesium, zinc, alkaline phosphatase, parathyroid hormone (PTH), and bone mineral density (BMD) were evaluated.

Sixty adolescents and 60 adults were assessed. At T0, there was no significant difference between the groups' serum 25(OH)D levels (G1 21.87 + 7.52 ng/mL, G2 21.73 + 7.60 ng/mL, p = 0.94) or sun exposure (G1 17 ± 2.0 min/day, G2 13.2 ± 5.2 min/day, p = 0.85). G1 had high levels of inadequacy of calcium (66.7%), phosphorous (80.0%), and zinc (18.3%) at T0 and had a significant fall in their 25(OH)D (p < 0.01) and magnesium (p < 0.01) levels from T1 to T2. G2 saw a significant lowering of their serum zinc levels from T0 to T1 and T2 (T1 p < 0.01; T2 p < 0.01). In both groups, there was a significant rise in PTH from T1 to T2 (G1 p = 0.04, G2 p = 0.02) and from T0 to T2 (G1 and G2 p < 0.01). In G2, 40.4% of individuals with osteopenia and osteoporosis presented inadequacy of 25(OH)D.

RYGB was found to worsen the inadequacy of micronutrients related to bone metabolism and was associated with secondary hyperparathyroidism and low BMD values, especially among the adolescents. The irreversible damaging effects of obesity on bone metabolism can occur in adolescence.