Bone loss in adolescents after bariatric surgery

Abstract

Objective: To evaluate bone loss in adolescents after Roux-en-Y gastric bypass surgery and to determine the extent to which bone loss was related to weight loss. We hypothesized that adolescents would lose bone mass after surgery and that it would be associated with weight loss.

Patients and methods: We conducted a retrospective case review of 61 adolescents after bariatric surgery. Whole-body bone mineral content (BMC) and density (BMD) were measured by dual-energy radiograph absorptiometry, and age- and gender-specific BMD z scores were calculated. Measurements were obtained when possible before surgery and then every 3 to months after surgery for up to 2 years. Data were analyzed by using a mixed-models approach, and regression models were adjusted for age, gender, and height.

Results: Whole-body BMC, BMD z score, and weight decreased significantly over time after surgery (P < .0001 for all). In the first 2 years after surgery, predicted values on the basis of regression modeling for BMC decreased by 7.4%, and BMD z score decreased from 1.5 to 0.1. During the first 12 months after surgery, change in weight was correlated with change in BMC (r = 0.31; P = .02). Weight loss accounted for 14% of the decrease in BMC in the first year after surgery.

Conclusion: Bariatric surgery is associated with significant bone loss in adolescents. Although the predicted bone density was appropriate for age 2 years after surgery, longer follow-up is warranted to determine whether bone mass continues to change or stabilizes.

Figures

FIGURE 1

Weight (A), BMC (B), and BMD z score (C) over time after bariatric surgery. Lines represent the 61 patients. The bold line is the predicted value for the regression characterizing change over time.