No abstract

Investigation of the physiologic relevance of bone marrow adipose tissue (BMAT) during growth may promote understanding of the bone-fat axis and confluence with metabolic factors. The objective of this pilot investigation was two-fold: (1) to evaluate the relationships among total body fat, bone mineral content (BMC) and femoral BMAT during childhood and underlying metabolic determinants and (2) to determine if the relationships differ by race. Participants included white and non-Hispanic black girls (n=59) ages 4–10 years. Femoral BMAT volume was measured by magnetic resonance imaging, BMC and body fat by dual-energy X-ray absorptiometry. Metabolic parameters were assessed in the fasted state. Total fat and BMC were positively associated with BMAT; however, simultaneous inclusion of BMC and body fat in the statistical model attenuated the association between BMC and BMAT. Differences in BMAT volume were observed, non-Hispanic black girls exhibiting marginally greater BMAT at age eight (P=0.05) and white girls exhibiting greater BMAT at age ten (P<0.001). Metabolic parameters conferred differential impact by race, such that, a positive association for BMAT and leptin (P=0.02) and adiponectin (P=0.002) in white girls while BMAT and insulin were inversely related in non-Hispanic black girls (P=0.008). Our findings revealed a positive relationship between BMAT, body fat and BMC, although body fat, respective to leptin, contributed partly to the relationship between BMAT and BMC. Despite large differences in total fat between non-Hispanic black and white, the relationship between BMAT and BMC was similar to white girls. However, this relationship appeared to be impacted through different mechanisms according to race.

Objectives Obesity prevalence among African American (AA) girls is higher than that of other groups. As typical calorie-restriction obesity treatment strategies have had limited success, alterations in macronutrient composition might effectively improve metabolic outcomes in this population and impact future body composition trajectories. The objective was to evaluate the efficacy of a moderately restricted carbohydrate (CHO) versus a standard CHO diet on weight/fat loss and metabolic parameters in overweight/obese AA girls aged 9–14 years. Methods A total of 26 AA girls (ranging from 92nd BMI percentile and above) were assigned to either a reduced- (SPEC: 42% calories from CHO, n=12) or a standard- (STAN: 55% of calories from CHO, n=14) CHO diet (protein held constant) for 16-weeks. All meals were provided and clinically tailored to meet the estimated energy requirements (REE × 1.2 in eucaloric phase and REE × 1.2 – 1000kcal in energy deficit phase). The first five-weeks encompassed a eucaloric phase evaluating metabolic changes in the absence of weight change. The subsequent 11-weeks were hypocaloric (1000kcal/d deficit) in effort to promote weight/fat loss. Meal tests were performed during the eucaloric phase for metabolic analyses. Dual-energy x-ray absorptiometry (DXA) was used to evaluate body composition. Results Both groups had reductions in weight/adiposity but the difference did not reach significance. The solid meal test indicated improved glucose/insulin homeostasis on the SPEC diet up to three hours post-ingestion. In addition, significantly lower triglycerides (p<0.001) were observed on the SPEC diet. Conclusions Dietary CHO reduction favorably influences metabolic parameters but did not result in greater weight/fat loss relative to a standard diet in obese AA girls. Future research is needed to determine long-term effectiveness of a reduced CHO diet on glucose and insulin homeostasis and how it may apply to weight maintenance/fat loss during development alone and/or in combination with additional weight loss/metabolic improvement strategies.

The objectives were to determine the effect of macronutrient modification on vitamin D status and if change in 25-hydroxy-vitamin D concentration influences components of metabolic syndrome in obese African American girls. Methods. Five-week intervention using reduced CHO (43% carbohydrate; 27% fat: SPEC) versus standard CHO (55% carbohydrate; 40% fat: STAN) eucaloric diet. Subjects were 28 obese African American females, aged 9–14 years. Dual energy X-ray absorptiometry and meal test were performed at baseline and five weeks. Results. Approximately 30% of girls had metabolic syndrome. Serum 25OHD increased in both groups at five weeks [STAN: 20.3 ± 1.1 to 22.4 ± 1.1 (P < 0.05) versus SPEC: 16.1 ± 1.0 to 16.8 ± 1.0 (P = 0.05)]. The STAN group, increased 25OHD concentration over five weeks (P < 0.05), which was positively related to triglycerides (P < 0.001) and inversely associated with total cholesterol (P < 0.001) and LDL (P < 0.001). The SPEC group, had increase in 25OHD (P = 0.05), which was positively related to fasting insulin (P < 0.001) and insulin sensitivity while inversely associated with fasting glucose (P < 0.05). The contribution of vitamin D status to metabolic syndrome parameters differs according to macronutrient intake. Improvement in 25OHD may improve fasting glucose, insulin sensitivity, and LDL; however, macronutrient intake warrants consideration.

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.