Reduced-carbohydrate, weight loss diet is associated with greater bone mineral content in obese African-American girls

Abstract

Background: Postprandial insulinemia the related physiologic response, associated with a high carbohydrate meal, may impact the bone-fat axis. In the context of dietary intervention such metabolic challenges, may impart significant influence. This may be particularly salient in African American females who have exaggerated acute insulin response and high propensity for adipose tissue accrual. The objective of this study was to evaluate the association of a standard-versus reduced-carbohydrate diet on bone mineral content in obese African American females. Methods: This dietary intervention study included 26 African American girls (≥96th BMI percentile), ages eight to 15 years. All of the meals were provided and tailored to meet the estimated energy requirements in a weight stable (eucaloric, five weeks), followed by a weight loss (1000 kcal deficit, 11 weeks) phase by random assignment to either a reduced-(42%, n=11) or a standard-(55%, n=15) carbohydrate diet for 16 weeks. DXA was used to evaluate body composition at baseline and after each diet phase. The contribution of diet to bone mineral content after each diet phase was evaluated using multiple linear regression analyses, controlling for baseline bone mineral content and fat mass index. The contribution of insulin and osteocalcin (a marker of bone deposition) to bone mineral content were also investigated by diet group at baseline and after the weight stable diet phase. Results: Dietary carbohydrate proportion significantly contributed to bone mineral content, such that consumption of the reduced-carbohydrate diet was associated with greater bone mineral content after the weight loss phase. After the weight stable phase of the study, both insulin and osteocalcin significantly contributed to bone mineral content (p<0.05) in those on the reduced-carbohydrate diet only. Conclusions: A reduced relative to standard carbohydrate diet to promote weight loss was associated with increased bone mineral content in obese African American females. Optimization of skeletal maturation processes is an important consideration when designing weight loss interventions among this age group. Our support the need for careful evaluation of macronutrient profile.