Bone mineral mass in overweight and obese children: diminished or enhanced?

Adolescent obesity incurs adult skeletal deficits in murine induced obesity model

Adolescent obesity has risen dramatically in the last few decades. While adult obesity may be osteoprotective, the effects of obesity during adolescence, which is a period of massive bone accrual, are not clear. We used a murine model of induced adolescent obesity to examine the structural, mechanical, and compositional differences between obese and healthy weight bone in 16-week-old female C57Bl6 mice. We also examined the effects of a return to normal weight after skeletal maturity (24 weeks old). We found obese adolescent bone exhibited decreased trabecular bone volume, increased cortical diameter, increased ultimate stress, and increased brittleness (decreased plastic energy to fracture), similar to an aging phenotype. The trabecular bone deficits remained after return to normal weight after skeletal maturity. However, after returning to normal diet, there was no difference in ultimate stress nor plastic energy to fracture between groups as the normal diet group increased ultimate stress and brittleness. Interestingly, compositional changes appeared in the former high-fat diet mice after skeletal maturity with a lower mineral to matrix ratio compared to normal diet mice. In addition there was a trend toward increased fluorescent advanced glycation endproducts in the former high-fat diet mice compared to normal diet mice but this did not reach significance (p < 0.05) due to the large variability. The skeletal consequences of adolescent obesity may have lasting implications for the adult skeleton even after return to normal weight. Given the rates of adolescent obesity, skeletal health should be a concern.

Genetic variants in the FAM3C gene are associated with lipid traits in Chinese children

BACKGROUND

Previous studies have related FAM3C gene with childhood bone health, and the regulation of lipid metabolism in hepatocytes. The present case-control study aimed to analyze the association of FAM3C genetic variants with overweight/obesity and lipid traits among Chinese children.

METHODS

Two genetic variants (rs7776725 and rs7793554) within the FAM3C gene were genotyped in 3305 Chinese children aged 6-18 years.

RESULTS

In the whole study population, the T-allele of rs7776725 and A-allele of rs7793554 within the FAM3C gene were associated with 40.2% (95% CI: 11.6-76.1%; P = 0.004) and 29.1% (6.9-56.0%; P = 0.008) increased risk of dyslipidemia, higher triglyceride (P = 0.014 and P = 0.001) and lower HDL-C (P = 0.015 and P = 0.003). In addition, we found that rs7776725 interacted with sex on dyslipidemia (P_{for interaction} = 0.004), and sex-stratified analyses showed that it was significantly associated with dyslipidemia only in girls (P = 8.78 × 10^-5). The variant also showed nominally significant interactions with sex on total cholesterol and LDL-C (P_{for interaction} = 0.012 and 0.008).

CONCLUSION

We found that FAM3C genetic variants were associated with dyslipidemia and lipid traits among Chinese children. In addition, we found significant gene-by-sex interactions. Our findings provided evidence supporting the role of FAM3C gene in regulating lipid metabolism in humans.

IMPACT

FAM3C genetic variants were associated with dyslipidemia and lipid traits among Chinese children. In addition, we found significant gene-by-sex interactions. FAM3C/rs7776725 was associated with dyslipidemia and lipid traits only in girls. Our findings provided evidence supporting the role of FAM3C gene in regulating lipid metabolism in humans.

Skeletal Effects of Nine Months of Physical Activity in Obese and Healthy Weight Children

PURPOSE

Obesity during adolescence has multisystem health consequences. The objective of this work was to determine whether preadolescent overweight/obese children's bones respond to a 9-month physical activity intervention by increasing bone density similar to healthy weight children.

METHODS

Participants included overweight/obese (BMI > 85%) and healthy weight (15% < BMI < 85%) preadolescents (8-9 yr old). Participants in the physical activity group participated in a 9-month physical activity curriculum every day after school. The wait list control group received no intervention. Both groups had overweight/obese children and healthy weight controls. Whole-body bone mineral content, area, and bone mineral apparent density (BMAD) were assessed using dual x-ray absorptiometry) at the beginning and end of the 9-month trial in the physical activity and control group.

RESULTS

Overweight/obese preadolescent children had higher BMAD than healthy weight children (P < 0.001 for spine, leg, and whole body). However, the density/weight (BMAD/lean mass) was lower in overweight/obese children than that in healthy weight children, indicating that the density of bones in overweight/obese children may not compensate sufficiently for the excessive load due to weight. The change in BMAD over 9 months was greater in healthy weight children than overweight/obese children in the whole body and leg, but not the lumbar spine. Physical activity caused a site-specific increase in bone density, affecting the legs more than the lumbar spine, but there was no significant difference in the effect of exercise between the healthy weight and the overweight/obese group.

CONCLUSIONS

The smaller change in BMAD over the 9 months and lower BMAD per unit lean mass in overweight/obese compared with healthy weight children may indicate a slower rate of bone mass accrual, which may have implications for bone health during skeletal growth in obese/overweight children.

Bone Mineral Density of Femur and Lumbar and the Relation between Fat Mass and Lean Mass of Adolescents: Based on Korea National Health and Nutrition Examination Survey (KNHNES) from 2008 to 2011

It is most important to reach the maximum bone density in the childhood period to prevent developing osteoporosis; it is widely known that increased body weight has a positive correlation with bone density and that even though both the fat mass and lean mass have a significant impact on bone density, the latter mass has more importance for adults. Therefore, the study analyzed to identify the relationship between bone density and both fat mass and lean mass of Korean adolescents. Subjects were chosen among 21,303 people from the Korea National Health and Nutrition Examination Survey (KNHNES) between 2008 and 2011 that took a bone density checkup; as a result, 1454 teenagers aged between 12 and 18 were selected. Data analysis was performed in SAS ver. 9.4 (SAS Institute Inc., Cary, NC, USA) following the KNHNES and the weighted complex sample analysis was conducted; body fat mass and lean mass were divided into quintile groups, and to figure out the differences in bone density that were analyzed in six models adjusted by body weight (kg) and walking (yes/no), muscle strengthening exercises (yes/no), nutrition (intake of ca (g), and serum vitamin D (ng/mL)). Then, the generalized linear model (GLM) and trend test were conducted for each gender with a significance level of 0.05. The bone density differences of fat mass and lean mass were analyzed. The result of Model 6 considering all correction variables is as follows; in the case of male adolescents, the total femur and lumbar spine showed a significant difference (F = 13.120, p < 0.001; F = 12.900, p < 0.001) for fat mass, and the trend test showed that the figures significantly decreased (β = −0.030, p < 0.001; −0.035, p < 0.001). Meanwhile, for lean mass, the total femur and lumbar spine had a significant difference (F = 16.740, p < 0.001; F = 20.590, p < 0.001) too, but the trend test showed a significant increase (β = 0.054, p < 0.001; 0.057, p < 0.001). In the case of female adolescents, the lumbar spine (F = 3.600, p < 0.05) for lean mass showed a significant difference, and it also significantly rose in the trend test too (β = 0.020, p < 0.01). To sum up the results, for male adolescents, the bone density differences for fat mass (FM) and lean mass (LM) all had significant differences, but for female adolescents, only the lumbar spine for LM showed such a result. Meanwhile, both genders showed that LM had a more positive impact on bone density than FM.

Adiposity is not beneficial to bone mineral density in 0-5 year old Chinese children: The Jiangsu bone health study

OBJECTIVE

Data on obesity in relation to bone mineral density(BMD) in infants and preschool children were sparse in China. The objective of this study was to examine the associations between body mass index (BMI) and BMD.

SUBJECTS AND METHODS

This was a large population-based multicenter study in which the representative children aged 0-5 years were recruited from 13 Children's Health Care Centers by a stratified cluster random-sampling method in Jiangsu Province, China. BMD was measured by using quantitative ultrasound. The association of BMD with BMI and obesity were evaluated using multiple linear regression and logistic regression analysis taking into account the effects of confounders. The relations between age, weight, height, BMI and BMD were analyzed by using Pearson's correlation and further tested using partial correlation in the additive model.

RESULTS

A total of 5,289 children (2786 boys and 2503 girls) were recruited. The BMD was positively linear relation with age, length/height, and was inversely linear relation with BMI (r=0.711, P<0.001; r=0.727, P<0.001; r=-0.318, P<0.001, respectively). The BMD gradually increased when the weight was in the range within 21.2kg, but started to gain slowlyand even decreased when the weight was over 21.2kg. After adjusting for confounders, compared with control group, children with obesityhad higher odds of low BMD (OR 95%CI: 2.73 (1.57, 4.76), P<0.001), the speed of sound (SOS)value in children with obesity was lower 47.45 (β=-47.45, 95%CI=-85.07, -9.83, P=0.013).

CONCLUSIONS

Adiposity was not advantageous for bone mineral density in 0-5-year-old Chinese children.

Bone mineral density and vitamin D status in children with remission phase of steroid-sensitive nephrotic syndrome

Children with idiopathic nephrotic syndrome are primarily treated with glucocorticoids (GCs), but long-term GC use can lead to undesired side effects. We investigated the bone mineral density (BMD) and 25-hydroxyvitamin D (25-OH D) levels in children with the remission phase of steroid-sensitive nephrotic syndrome (SSNS). This study included 32 patients with SSNS who had not received GC treatment in the last 6 months and a control group of 20 healthy children. Serum levels of calcium, phosphate, alkaline phosphatase, 25-(OH)D, and parathyroid hormone (PTH) were measured. BMD was determined in the lumbar spinal region using dual-energy X-ray absorptiometry (DEXA). Serum 25-(OH)D levels were lower in the SSNS patients than in the healthy children (P <0.05), with 22 patients (68.8%) having Z-scores <-1. The Z-scores were positively correlated with 25-(OH)D levels (r = 0.424, P <0.05). PTH levels were higher in patients with osteoporosis than in patients with Z-scores ≥-1 (P <0.05). Bone mineral content and BMD were positively correlated with the age of diagnosis (P <0.01). Receiver-operating characteristic curve analysis showed that the cutoff value of 25-(OH)D levels for predicting low BMD was 14.67 ng/mL with a sensitivity of 90% and a specificity of 64%. The area under the curve (AUC ± standard error) was 0.868 ± 0.064 (95% confidence interval: 0.742-0.994, P = 0.001). Decreased 25-(OH)D levels and the negative effects of long-term GC treatment on BMD persist in SSNS remission phase. Levels of 25-(OH)D <14.67 ng/mL could predict abnormal DEXA scans in children with SSNS remission phase.

Effects of interventions with a physical activity component on bone health in obese children and adolescents: a systematic review and meta-analysis

Given the rise in pediatric obesity, clarifications on the relationship between obesity and bone health and on the impact of structured intervention on this relationship are needed. This systematic review and meta-analysis investigated the effect of obesity on bone health and assessed the effect of structured intervention in children and adolescents with obesity. Medline complete, OVID, CINAHL, EMBASE and PubMed databases were searched for studies on obesity and bone health variables up to September 2016, then an update occurred in March 2016. Search items included obesity, childhood, dual energy X-ray absorptiometry and peripheral quantitative computed tomography. Twenty-three studies (14 cross-sectional and nine longitudinal) matched the inclusion criteria. Results from the meta-analysis (cross-sectional studies) confirmed that children and adolescents with obesity have higher bone content and density than their normal weight peers. Results from longitudinal studies remain inconclusive as only 50% of the included studies reported a positive effect of a structured intervention program on bone health. As such, the meta-analysis reported that structured intervention did not influence bone markers despite having beneficial effects on general health in youth with obesity.

Investigating the Prevalence of Low Bone Mass in Children of Southern Iran and Its Associated Factors

BACKGROUND

Improving peak bone mass and bone strength in the first years of life and enhancing it during young adulthood could prevent osteoporosis and fractures in the last years of life. We evaluated the prevalence of low bone mass in the lumbar and femoral neck and its associated factors in southern Iranian children.

METHODS

This is a cross-sectional study on healthy Iranian children aged 9 - 18 years old during 2011 - 2012. Dual energy X-ray absorptiometry (DEXA) was used for measuring bone mineral density (BMD). BMD Z-score ≤ -2 was considered as low. Anthropometric data, physical activity, sun exposure, puberty, and mineral biochemical parameters were assessed. Data were analyzed using SPSS v.15.

RESULTS

477 normal children, including 236 (49.5%) girls and 241 (50.5%) boys, aged 13.8 ± 2.7 years were enrolled. Prevalence of low bone mass (LBM) in the femoral and lumbar region was 10.7% and 18.7%, respectively. The prevalence of LBM in femur of girls is twice more than boys. Fat mass index, BMI Z-score, and physical activity were associated with lumbar low bone mass. BMI Z-score and physical activity were associated with femoral low bone mass.

CONCLUSIONS

High prevalence of low bone mineral density in children 9 to 18 years in south of the country is concerned and is needed to plan for prevention and treatment. BMI-Z score, fat mass index, and physical activity were the 3 most important preventive factors in developing low bone mass in children.

The Role of Overweight and Obesity on Bone Health in Korean Adolescents with a Focus on Lean and Fat Mass

As the associations between pediatric overweight/obesity and bone health remain controversial, we investigated the effects of overweight/obesity as well as lean mass (LM) and fat mass (FM) on bone parameters in adolescents. Bone parameters were evaluated using dual-energy X-ray absorptiometry (DXA) data of 982 adolescents (aged 12-19 years) from the Korea National Health and Nutrition Examination Survey (2009-2010). Z-scores for LM, FM, bone mass, bone mineral density (BMD), and bone mineral apparent density (BMAD) using Korean pediatric reference values were used for analysis. Adolescents with overweight/obesity had significantly higher bone mass and density of the total-body-less-head (TBLH), lumbar spine, and femur neck than underweight or normal-weight adolescents (P < 0.001) after adjusting for vitamin D deficiency, calcium intake, and insulin resistance in both sexes. LM was positively associated with bone parameters at all skeletal sites in both sexes (P < 0.001). FM was negatively related to TBLH BMD in boys (P = 0.018) but was positively associated to BMD and BMAD of the lumbar spine and femur neck in girls. In conclusion, overweight/obesity and LM play a positive role in bone health in adolescents. The effect of FM on bone parameters is sex- and site-specific.

Differences in bone mineral density between normal-weight children and children with overweight and obesity: a systematic review and meta-analysis

OBJECTIVE

This study examines the differences in bone mineral density between normal-weight children and children with overweight or obesity.

METHODS

A systematic review and meta-analysis of observational studies (published up to 22 June 2016) on the differences in bone mineral density between normal-weight children and overweight and obese children was performed. Results were pooled when possible and mean differences (MDs) were calculated between normal-weight and overweight and normal-weight and obese children for bone content and density measures at different body sites.

RESULTS

Twenty-seven studies, with a total of 5,958 children, were included. There was moderate and high quality of evidence that overweight (MD 213 g; 95% confidence interval [CI] 166, 261) and obese children (MD 329 g; 95%CI [229, 430]) have a significantly higher whole body bone mineral content than normal-weight children. Similar results were found for whole body bone mineral density. Sensitivity analysis showed that the association was stronger in girls.

CONCLUSIONS

Overweight and obese children have a significantly higher bone mineral density compared with normal-weight children. Because there was only one study included with a longitudinal design, the long-term impact of childhood overweight and obesity on bone health at adulthood is not clear.

Gynecologic and Obstetric Consequences of Obesity in Adolescent Girls

In the past few decades, there has been an overwhelming increase in childhood and adolescent obesity worldwide. Besides the well recognized cardiometabolic complications and other physical conditions associated with obesity, during adolescence, it causes psychological and social distress in a period of life that is already sensitive for a girl. This in turn increases their risk of low self-esteem and depression. Furthermore, obesity diminishes health-related quality of life and years of life. Overweight and obese teenagers are more likely to have gynecologic and obstetric complications, during adolescence and also later in life. Consequences of obese and overweight childhood and adolescence include sexual maturation and reproductive dysfunction, alterations in menstruation, dysmenorrhea, risky sexual behavior, and inefficient use of contraception, polycystic ovary syndrome, bone density abnormalities, macromastia, and an increased risk of breast and endometrial cancer. Obese adolescents are at greater risk of pregnancy and perinatal complications, such as preeclampsia, gestational hypertension and preeclampsia, gestational diabetes mellitus, primary cesarean delivery, and induction of labor, to mention a few. Evidence shows that infants born to obese teenagers are also more likely to have complications including preterm or post-term delivery, small-for-gestational age newborns, macrosomia, meconium aspiration, respiratory distress, and even stillbirth, among others. This comprehensive review focuses on the gynecological and obstetric consequences of obesity in adolescent girls.

Evaluation of Hip/HeightP Ratio as an Index for Adiposity and Metabolic Complications in Obese Children: Comparison with Waist-related Indices

Aim: To investigate whether body adiposity index (BAI; hip/height^1.5–18), pediatric BAI (BAIp; hip/height^0.8–38), and other hip/height^P ratios are useful in obese children.

Method: Ninety obese Japanese children, 55 boys and 35 girls, who visited our University Clinic, were enrolled. The age was 9.92 ± 2.6 (mean ± SD) years, and the percentage overweight (POW) was 51.6 ± 18.8%. We set the power value of the hip/height^P 0, 0.5, 0.8, 1, 1.5, and 2 and studied the association with overweight indices, biochemical data, and fat area measured by computed tomography. Waist, waist/height ratio, and waist/hip ratio were also evaluated.

Results: Hip/height and hip/height^0.8 (BAIp) were more closely correlated with POW, body mass index percentile, and percentage body fat than hip/height^1.5 (BAI). The correlation coefficient of hip/height with POW (r = 0.855) was the highest among the studied hip/height^P indices. The approximate line to predict POW was 411 × hip/height−207. The waist/height was also highly correlated with POW (r = 0.879). Hip and hip/height^0.5 were more closely correlated with visceral fat area than hip/height, BAIp, and hip/height^1.5. Hip and hip/height^0.5 were significantly correlated with insulin. Only hip was also significantly associated with dyslipidemia. All hip/height^P indices were not significantly correlated with alanine aminotransferase (ALT). Waist was significantly correlated with serum lipids, ALT, and insulin.

Conclusion: Hip/height and BAIp are better markers for overweight (adiposity) in obese children than BAI. However, hip/height, BAIp, and BAI are not useful to predict metabolic complications. Waist appears to be the best index for obese children overall at this time.

Bone-adiposity cross-talk: implications for pediatric obesity. A narrative review of literature

The rising prevalence of overweight and obesity among pediatric populations has become a major global concern. The objective of this review is to demonstrate potential interactions between the products released by fat tissue and the hormonal production of bone tissue in obese children and adolescents. Advancing the understanding of the complex interactions between adipocyte and osteocyte activities may contribute to the mechanistic understanding of the body's responses to weight loss during adolescence. This knowledge could also reveal any side effects encountered with these interventions. Currently, the concept of bone-adiposity crosstalk has not been fully elucidated, and the mechanisms remain controversial. Understanding the local interactions between the released products by fat tissue and hormones produced in bone tissue requires further investigations.

Physical activity and bone health in schoolchildren: the mediating role of fitness and body fat

BACKGROUND

The relationship between physical activity (PA) and bone health is well known, although the role of percent body fat (%BF) and fitness as confounders or mediators in this relationship remains uncertain.

OBJECTIVE

To examine whether the association between PA and bone mineral content (BMC) is mediated by %BF and cardiorespiratory fitness (CRF).

METHODS

In this cross sectional study, BMC, total %BF (by DXA), vigorous PA (VPA), CRF, age and height were measured in 132 schoolchildren (62 boys, aged 8-11 years). ANCOVA was used to test differences in BMC by %BF, CRF and VPA, controlling for different sets of confounders. Simple mediation analyses and serial multiple mediation analyses were fitted to examine whether the relationship between PA and BMC is mediated by %BF and fitness.

RESULTS

Children with high %BF had higher total body BMC than their peers after controlling for all sets of confounders. Children with good CRF or VPA had significantly less total body BMC after controlling for age and sex but in children with good CRF this inverse relation disappeared after adjusting by %BF. %BF and CRF both act as a full mediator in the association between VPA and BMC, after inclusion of the potential confounders in the models.

CONCLUSION

Fitness and %BF seem to have a mediator role on the relationship between physical activity and bone mass.

Changes in Bone Biomarkers, BMC, and Insulin Resistance Following a 10-Week Whole Body Vibration Exercise Program in Overweight Latino Boys

PURPOSE

With the childhood obesity epidemic, efficient methods of exercise are sought to improve health. We tested whether whole body vibration (WBV) exercise can positively affect bone metabolism and improve insulin/glucose dynamics in sedentary overweight Latino boys.

METHODS

Twenty Latino boys 8-10 years of age were randomly assigned to either a control (CON) or 3 days/wk WBV exercise (VIB) for 10-wk.

RESULTS

Significant increases in BMC (4.5 ± 3.2%; p=0.01) and BMD (1.3 ± 1.3%; p<0.01) were observed for the VIB group when compared to baseline values. For the CON group BMC significantly increased (2.0 ± 2.2%; p=0.02), with no change in BMD (0.8 ± 1.3%; p=0.11). There were no significant between group changes in BMC or BMD. No significant change was observed for osteocalcin and (collagen type I C-telopeptide) CTx for the VIB group. However, osteocalcin showed a decreasing trend (p=0.09) and CTx significantly increased (p<0.03) for the CON group. This increase in CTx was significantly different between groups (p<0.02) and the effect size of between-group difference in change was large (-1.09). There were no significant correlations between osteocalcin and measures of fat mass or insulin resistance for collapsed data.

CONCLUSION

Although bone metabolism was altered by WBV training, no associations were apparent between osteocalcin and insulin resistance. These findings suggest WBV exercise may positively increase BMC and BMD by decreasing bone resorption in overweight Latino boys.

Higher circulating parathormone is associated with smaller and weaker bones in obese children

Obese children have disadvantageous bone geometry, bone of low quality, and reduced strength at non-weight-bearing skeletal sites. The aim of our study was to investigate the role of parathormone (PTH) and the Wnt/β-catenin signaling pathway and its inhibitors, sclerostin and Dickkopf-1 (DKK1), as negative modulators of fat mass on bone. This was a cross-sectional observational study performed in 44 (26 males and 18 females) obese subjects, aged 11.41 ± 2.61 years. Thirty-seven normal-weight, healthy children (22 males and 15 females) of the same chronological age served as controls for the biochemical parameters and bone markers, while the data on bone geometry were evaluated according to our normative data obtained previously in a group of 325 control children. Digitalized X-rays were evaluated at the level of the second metacarpal bone for the determination of bone geometry: total cross-sectional area (TCSA), cortical area (CA), medullary area (MA), and bone strength (bending breaking resistance index [BBRI]). Serum bone markers (intact procollagen-1N-terminal propeptide [P1NP] and serum carboxy-terminal telopeptide of collagen-1 [CTX]), sclerostin, DKK1, PTH, 25-hydroxyvitamin D and were also measured. Data for TCSA, CA, MA, and BBRI are expressed as a standard deviation score in order to normalize them for age and sex. TCSA (mean ± SD, -2.92 ± 2.71), CA (-0.60 ± 0.82), MA (-0.45 ± 1.14), and BBRI (-2.65 ± 2.31) were all significantly smaller than in controls (p < 0.01). Serum PTH (36.27 ± 23.89 vs. 19.33 ± 11.37 pg/mL) and CTX (1.55 ± 0.44 vs. 1.34 ± 0.46 ng/mL) were significantly increased (p < 0.05) in the obese children compared to controls, while sclerostin was significantly decreased (24.67 ± 10.06 vs. 30.42 ± 11.01 pmol/L, p < 0.05). P1NP was also significantly increased (p < 0.01). PTH was negatively correlated with TCSA, CA, and BBRI. Bone turnover is higher in obese children than in controls, and this is associated with smaller and apparently weaker bones. Higher PTH and lower sclerostin levels may be responsible for these findings.

Geometric indices of hip bone strength in obese, overweight, and normal-weight adolescent girls

The aim of this study was to compare hip bone strength indices in obese, overweight, and normal-weight adolescent girls using hip structure analysis (HSA). This study included 64 postmenarcheal adolescent girls (14 obese, 21 overweight, and 29 normal weight). The 3 groups (obese, overweight, and normal weight) were matched for maturity (years since menarche). Body composition and bone mineral density (BMD) of whole body, lumbar spine, and proximal femur were assessed by dual-energy X-ray absorptiometry (DXA). To evaluate hip bone strength, DXA scans were analyzed at the femoral neck (FN) at its narrow neck (NN) region, the intertrochanteric (IT), and the femoral shaft (FS) by the HSA program. Cross-sectional area and section modulus were measured from hip BMD profiles. Total hip BMD and FN BMD were significantly higher in obese and overweight girls in comparison with normal-weight girls (p < 0.05). However, after adjusting for weight, using a one-way analysis of covariance, there were no significant differences among the 3 groups regarding HSA variables. This study suggests that in obese and overweight adolescent girls, axial strength and bending strength indices of the NN, IT, and FS are adapted to the increased body weight.

Bone mineral density, hip bone geometry, and calcaneus trabecular bone texture in obese and normal-weight children

Our study aimed at comparing bone mineral density (BMD), geometric indices of hip bone strength, and indices of trabecular bone texture at the calcaneus in obese and normal-weight children. Fifty-three obese children (10.3 ± 1.4 yr) and 24 normal-weight children (10.4 ± 1.5 yr) participated in this study. Body composition, bone mineral content, and BMD at whole body (WB), lumbar spine (L2-L4), total forearm, and proximal femur (total hip [TH] and femoral neck [FN]) were measured by dual-energy X-ray absorptiometry (DXA). Bone geometry of the hip was evaluated by the hip structure analysis (HSA) program. DXA scans were analyzed at the FN at its narrowest region and the femoral shaft (FS) by the HSA program. Cross-sectional area (CSA) and section modulus (Z) were measured from hip BMD profiles. Texture analysis was performed on digitized radiographs of the calcaneus to assess trabecular bone microarchitecture, and the result was expressed as Hmean. WB BMD, L2-L4 BMD, TH BMD, and FN BMD were significantly higher in obese children compared with normal-weight peers (p < 0.05). FN Z and FS Z were not significantly different between the 2 groups, whereas Hmean parameter was significantly lower in obese children compared with normal-weight peers (p < 0.001). After adjustment for body weight, obese children displayed lower WB BMD, FN CSA, FN Z, FS CSA, and FS Z compared with normal-weight children. This study suggests that BMD of WB and geometric indices of hip bone strength are not adapted to the increased body weight in obese children.

How does bone quality differ between healthy-weight and overweight adolescents and young adults?

BACKGROUND

Overweight youth have greater bone mass than their healthy-weight peers but sustain more fractures. However, it is unclear whether and how excess body fat influences bone quality in youth.

QUESTIONS/PURPOSES

We determined whether overweight status correlated with three-dimensional aspects of bone quality influencing bone strength in adolescent and young adult females and males.

METHODS

We categorized males (n=103; mean age, 17 years) and females (n=85; mean age, 18 years) into healthy-weight and overweight groups. We measured lean mass (LM) and fat mass (FM) with dual-energy x-ray absorptiometry (DXA). We used high-resolution peripheral quantitative CT to assess the distal radius (7% site) and distal tibia (8% site). Bone quality measures included total bone mineral density (Tt.BMD), total area (Tt.Ar), trabecular bone volume fraction (BV/TV), trabecular number (Tb.N), separation (Tb.Sp), and thickness (Tb.Th). We used multiple regression to compare bone quality between healthy-weight and overweight adolescents adjusting for age, ethnicity, limb length, LM, and FM.

RESULTS

Overweight males had higher (10%-21%) Tt.BMD, BV/TV, and Tb.N and lower Tb.Sp at the tibia and lower Tt.Ar at the radius than healthy-weight males. No differences were observed between overweight and healthy-weight females. LM attenuated the differences in bone quality between groups in males while FM negatively predicted Tt.BMD, BV/TV, Tb.N, and Tb.Th.

CONCLUSIONS

Our data suggest overweight males have enhanced bone quality compared with healthy-weight males; however, when group differences are interpreted in the context of the mechanostat theory, it appears bone quality of overweight adolescents adapts to LM and not to greater FM.

Small metacarpal bones of low quality in obese children

OBJECTIVE

It is still not known whether fat mass excess could exert a positive effect on bone. The aim of our study was to evaluate bone strength and quality in a group of overweight and obese children and adolescents by assessing bone geometry at metacarpal bones and ultrasound at phalangeal level.

DESIGN AND PATIENTS

This is a cross sectional observational study performed in 123 subjects, aged 11.2 ± 2.9 years.

MEASUREMENTS

Digitalized X-rays were evaluated at the level of the 2nd metacarpal bone for the determination of the outer (D) and inner (d) diameter, cortical area (CA), medullary endocortical area (EA), metacarpal index (MI) and bone strength (Bending Breaking Resistance Index; BBRI). A total of 98 subjects underwent amplitude dependent speed of sound (Ad-SOS) and bone transmission time (BTT) assessment by phalangeal ultrasonography.

RESULTS

SDs for each measured parameter were as follows: Males: D = -0.71 ± 0.95, d = -0·29 ± 0.86, CA = -0.69 ± 0.69, EA = -0.32 ± 0.79, Ad-SOS = -1.14 ± 0.91, BTT = -1.17 ± 1.11 and BBRI (417 ± 151 vs 495 ± 174 mm(3) ) were all significantly lower than in controls (P < 0.05). Females: D = -1.03 ± 1.06, d = -0.38 ± 0.92, CA = -0.91 ± 0.72, EA = -0.46 ± 0.79, Ad-SOS = -1.08 ± 1.11, BTT = -0.97 ± 1.07 and BBRI (342 ± 117 vs 649 ± 318 mm(3) ) were all significantly lower than in controls (P < 0.05).

CONCLUSIONS

Obese children show an unfavourable bone geometry and a bone of low quality and reduced strength compared to controls at a nonweight bearing skeletal site. This finding seems to support a detrimental effect of fat mass on bone and explain the frequent occurrence of wrist fractures in this group of children.

Longitudinal relationships between whole body and central adiposity on weight-bearing bone geometry, density, and bone strength: a pQCT study in young girls

Longitudinal relationships between adiposity (total body and central) and bone development were assessed in young girls. Total body and android fat masses were positively associated with bone strength and density parameters of the femur and tibia. These results suggest adiposity may have site-specific stimulating effects on the developing bone.

INTRODUCTION

Childhood obesity may impair bone development, but the relationships between adiposity and bone remain unclear. Failure to account for fat pattern may explain the conflicting results.

PURPOSE

Longitudinal associations of total body fat mass (TBFM) and android fat mass (AFM) with 2-year changes in weight-bearing bone parameters were examined in 260 girls aged 8-13 years at baseline. Peripheral quantitative computed tomography was used to measure bone strength index (BSI, square milligrams per quartic millimeter), strength-strain index (SSI, cubic millimeters), and volumetric bone mineral density (vBMD, milligrams per cubic centimeter) at distal metaphyseal and diaphyseal regions of the femur and tibia. TBFM and AFM were assessed by dual-energy x-ray absorptiometry.

RESULTS

Baseline TBFM and AFM were positively associated with the change in femur BSI (r = 0.20, r = 0.17, respectively) and femur trabecular vBMD (r = 0.19, r = 0.19, respectively). Similarly, positive associations were found between TBFM and change in tibia BSI and SSI (r = 0.16, r = 0.15, respectively), and femur total and trabecular vBMD (r = 0.12, r = 0.14, respectively). Analysis of covariance showed that girls in the middle thirds of AFM had significantly lower femur trabecular vBMD and significantly higher tibia cortical vBMD than girls in the highest thirds of AFM. All results were significant at p < 0.05.

CONCLUSIONS

Whereas baseline levels of TBFM and AFM are positive predictors of bone strength and density at the femur and tibia, higher levels of AFM above a certain level may impair cortical vBMD growth at weight-bearing sites. Future studies in obese children will be needed to test this possibility.

Relationship between markers of body fat and calcaneal bone stiffness differs between preschool and primary school children: results from the IDEFICS baseline survey

The aim of this study was to investigate the relationship between markers of body fat and bone status assessed as calcaneal bone stiffness in a large sample of European healthy pre- and primary school children. Participants were 7,447 children from the IDEFICS study (spread over eight different European countries), age 6.1 ± 1.8 years (range 2.1-9.9), 50.5 % boys. Anthropometric measurements (weight, height, bioelectrical impedance, waist and hip circumference, and tricipital and subscapular skinfold thickness) as well as quantitative ultrasonographic measurements to determine calcaneal stiffness index (SI) were performed. Partial correlation analysis, linear regression analysis, and ANCOVA were stratified by sex and age group: preschool boys (n = 1,699) and girls (n = 1,599) and primary school boys (n = 2,062) and girls (n = 2,087). In the overall study population, the average calcaneal SI was equal to 80.2 ± 14.0, ranging 42.4-153. The results showed that preschool children with higher body fat had lower calcaneal SI (significant correlation coefficients between -0.05 and -0.20), while primary school children with higher body fat had higher calcaneal SI (significant correlation coefficients between 0.05 and 0.13). After adjusting for fat-free mass, both preschool and primary school children showed an inverse relationship between body fat and calcaneal stiffness. To conclude, body fat is negatively associated with calcaneal bone stiffness in children after adjustment for fat-free mass. Fat-free mass may confound the association in primary school children but not in preschool children. Muscle mass may therefore be an important determinant of bone stiffness.

Geometric indices of hip bone strength in obese, overweight, and normal-weight adolescent boys

The aim of this study was to compare hip bone strength indices in obese, overweight, and normal-weight adolescent boys using hip structure analysis. After adjusting for weight, obese boys displayed lower intertrochanteric cross-sectional moment of inertia and femoral shaft cross-sectional moment of inertia and section modulus in comparison to normal-weight and overweight boys. This study suggests that in obese adolescent boys, femoral shaft bending strength is not adapted to the increased body weight.

INTRODUCTION

The influence of being obese or overweight on bone strength in adolescents remains controversial. The main aim of this study was to compare hip bone strength indices in obese, overweight, and normal-weight adolescent boys using hip structure analysis. The second aim of this study was to explore the influence of lean mass and fat mass on hip bone strength indices in the same population.

METHODS

This study included 70 adolescent boys (25 obese, 25 normal weight, and 20 overweight). The three groups (obese, overweight, and normal weight) were matched for maturity (Tanner stage) and age. Body composition and bone mineral density (BMD) were assessed by dual-energy X-ray absorptiometry (DXA). To evaluate hip bone strength, DXA scans were analyzed at the femoral neck (FN), the intertochanteric (IT), and the femoral shaft (FS) by the Hip Structure Analysis (HSA) program. Cross-sectional area (CSA), an index of axial compression strength, section modulus (Z), an index of bending strength, and cross-sectional moment of inertia (CSMI), an index of structural rigidity were measured from bone mass profiles.

RESULTS

Body weight, lean mass, fat mass and BMI were significantly higher in obese and overweight boys in comparison to normal-weight boys (P < 0.05). Total hip (TH) BMD and femoral neck (FN) BMD were significantly higher in obese and overweight boys in comparison to normal-weight boys (P < 0.05). After adjusting for age or maturation index, obese and overweight boys displayed significantly higher TH and FN BMD, CSA, CSMI, and Z of the three sites (FN, IT, and FS) in comparison to normal-weight boys (P < 0.05). However, after adjusting for weight, obese boys displayed significantly lower IT CSMI and FS CSMI and Z in comparison to normal-weight and overweight boys (P < 0.05).

CONCLUSIONS

This study suggests that in obese adolescent boys, intertrochanteric structural rigidity and femoral shaft structural rigidity and bending strength are not adapted to the increased body weight.

Adiposity and bone health in Spanish adolescents. The HELENA study

While the association of lean mass (LM) with bone mass is well understood, the association of fat mass (FM) with bone mass is controversial. Our results support that adolescents with higher levels of adiposity have greater bone mass, but this association is fully explained by their higher levels of LM.

INTRODUCTION

We aimed (1) to study the independent association of FM and LM with bone mass and (2) to study the differences in bone mass by weight status in adolescents, after controlling for relevant confounders, such as physical activity (PA), calcium intake, and LM.

METHODS

Participants were 330 adolescents (167 boys, 12.5-17.5 years) from the HELENA study. The relationships of FM (DXA, n = 330; BodPod, n = 282) and LM (DXA, n = 330) with different bone variables (whole body, total hip, lumbar spine, and femoral neck) were analyzed by linear regression, and differences between weight status were analyzed by ANCOVA.

RESULTS

Fat mass (DXA) was positively associated with bone variables in both sexes, after adjustment for height, calcium intake, and sexual maturation. Additional adjustment by PA slightly increases the associations. However, adjustment for LM inverted these associations. Similar results were obtained using BodPod instead of DXA for assessing FM. Overweight/obese adolescents had higher BMC than their non-overweight peers in most of regions studied. Additional adjustment for PA slightly increased the differences between weight status groups, while adjusting for LM inverted the associations. LM was strong and positively associated with all bone variables in both sexes. Additional adjustment for PA or FM did not change the results.

CONCLUSIONS

Adolescents with higher levels of adiposity have greater bone mass, but this association is explained by their higher levels of LM.

Hip bone strength indices in overweight and control adolescent boys

The influence of being overweight on bone strength in adolescents remains controversial. The aim of this study was to compare hip bone strength indices in overweight and control adolescent boys using hip structure analysis (HSA). This study included 25 overweight adolescent boys [body mass index (BMI) >25 kg/m(2)] and 31 maturation-matched controls (BMI <25 kg/m(2)). Body composition and bone mineral density were assessed by dual-energy X-ray absorptiometry (DXA). To evaluate hip bone strength, DXA scans were analyzed at femoral neck, intertrochanteric, and femoral shaft by the HSA program. Cross-sectional area (CSA), an index of axial compression strength, section modulus (Z), an index of bending strength, cross-sectional moment of inertia (CSMI), cortical thickness (CT), and buckling ratio (BR) were measured from bone mass profiles. Body weight, lean mass, fat mass, and BMI were higher in overweight boys compared to controls (P < 0.001). CSA, CSMI, and Z of the three sites (femoral neck, intertrochanteric, and femoral shaft) were higher in overweight boys compared to controls (P < 0.01). BR was not significantly different between the two groups at the three sites. After adjustment for either body weight, BMI, or fat mass, using a one-way analysis of covariance, there were no differences between the two groups regarding the HSA variables (CSA, Z, CSMI, CT, and BR). After adjusting for lean mass, overweight boys displayed higher values of femoral shaft CSA, CSMI, and Z in comparison to controls (P < 0.05). In conclusion, this study suggests that overweight adolescent boys have greater indices of bone axial and bending strength in comparison to controls at the femoral neck, the intertrochanteric, and the femoral shaft.

Influence of age and morphological characteristics on whole body, lumbar spine, femoral neck and 1/3 radius bone mineral apparent density in a group of Lebanese adolescent boys

The purpose of this study was to analyse the relationships between age, morphological characteristics (weight, height, body mass index (BMI), fat and lean mass), daily calcium intake (DCI), physical activity and bone mineral apparent density (BMAD) of the whole body (WB), lumbar spine (L2-L4), femoral neck (FN) and 1/3 radius in a group of Lebanese adolescent boys. This study included 60 Lebanese adolescent (16.8 ± 2.1 years old) boys. Body composition and bone mineral density (BMD) were assessed by dual-energy X-ray absorptiometry (DXA). BMAD values of the WB, L2-L4, FN and 1/3 radius were calculated. Physical activity and DCI were assessed using questionnaires. Age was positively related to WB, L2-L4 and 1/3 radius BMD and BMAD. Weight, lean mass and BMI were positively related to WB, L2-L4, FN and 1/3 radius BMD. Moreover, weight, lean mass and BMI were positively associated with L2-L4 and FN BMAD but not with BMAD of the WB and the 1/3 radius, while fat mass percentage was negatively associated with WB BMAD. In conclusion, this study shows that weight, lean mass and BMI are positively associated with BMAD of the weight-bearing bones (L2-L4 and FN) but not with BMAD of the WB and the 1/3 radius in adolescent boys.

Bone mineral content and density in overweight and control adolescent boys

The aim of this study was to compare bone mineral content (BMC) and areal bone mineral density (aBMD) in overweight and control adolescent boys. This study included 27 overweight (body mass index [BMI] > 25 kg/m²) adolescent (17.1 ± 2.1 yr old) boys and 29 maturation-matched (16.7 ± 2.0 yr old) controls (BMI< 25 kg/m²). Bone mineral area (BMA), BMC, and aBMD were assessed by dual-energy X-ray absorptiometry (DXA) at the whole body (WB), lumbar spine (L2-L4), total hip (TH), femoral neck (FN), and left forearm (ultra distal [UD], mid Radius, 1/3 Radius, and total Radius). Body composition (lean mass, fat mass, and fat mass percentage) was assessed also by DXA. The expressions WB BMC/height, WB aBMD/height, and WB BMAD were used to adjust for WB bone size. WB BMC, WB BMC/height, WB BMA, L2-L4 aBMD, TH aBMD, FN aBMD, and UD aBMD were higher in overweight boys compared with controls (p < 0.05). However, WB BMAD was lower in overweight boys compared with controls (p < 0.05). After adjustment for weight, lean mass, or BMI, using a one-way analysis of covariance, there were no differences between the 2 groups (overweight and controls) regarding bone characteristics (BMC, BMA, aBMD, BMC/height, aBMD/height, and BMAD of the WB and aBMD of the lumbar spine; the TH; the FN; and the forearm). In conclusion, this study shows that after adjusting for weight, lean mass, or BMI, there are no differences between overweight and control adolescent boys regarding aBMD values.

The accrual of bone mass during childhood and puberty

PURPOSE OF REVIEW

To assess factors that influence the tempo of bone mass accrual with emphasis on obesity, exercise, and nutritional factors.

RECENT FINDINGS

The prevalence of childhood obesity has increased dramatically throughout the world. Recent studies suggest that adiposity may be detrimental to development of bone strength parameters, and bone mass accrual during growth. Weight-bearing exercise during prepubertal and peripubertal period appears to enhance bone strength parameters. Maternal ultraviolet B radiation exposure and vitamin D status has been shown to have a positive effect on neonatal bone status, which appears to track up to the prepubertal period. Administration of vitamin D with or without calcium, but not calcium alone, during the prepubertal period might be an important 'window' for improving skeletal mineralization.

SUMMARY

Obesity in children appears to be detrimental to development of bone strength parameters and bone mass accrual. Weight-bearing exercise during prepubertal and peripubertal period and vitamin D supplementation during pregnancy, infancy, and peripubertal period might be important for bone mass accrual. However, adequately powered randomized controlled trials with follow-up into adulthood are needed to determine if these interventions improve the tempo of bone mass accrual.

Bone and fat relationships in postadolescent black females: a pQCT study

Despite adolescent black females experiencing the highest rates of obesity, the effect of excess fat mass on bone structure and strength in this population is unknown. Our findings in postadolescent black females suggest that excess weight in the form of fat mass may adversely influence cortical bone structure and strength.

INTRODUCTION

Although adolescent obesity has been associated with reduced bone structure and strength in white females, this relationship has not been studied in adolescent black females, a population experiencing the highest rates of obesity. Our objective was to compare bone structure and strength between postadolescent black females with normal and high levels of adiposity.

METHODS

Black females with ≤ 32% body fat were classified as normal body fat (NF; n = 33, aged 19.3 ± 1.3 years); females exceeding this cutoff were classified as high body fat (HF; n = 15, aged 19.0 ± 1.1 years). Using peripheral quantitative computed tomography, tibial and radial bones were scanned at the 4% (trabecular) and 20% (cortical) sites from the distal metaphyses. Fat-free soft-tissue mass (FFST) and %body fat were assessed by dual-energy X-ray absorptiometry.

RESULTS

After controlling for either FFST or body weight, the HF vs. NF group had lower total cross-sectional area (CSA; 9-17%), cortical CSA (6-15%), and strength-strain index (SSI; 13-24%) at the cortical site of the tibia (all p < 0.05). At the cortical site of the radius, the HF vs. NF group had lower total CSA (14%, p = 0.03), cortical CSA (9%, p = 0.04), and SSI (15%, p = 0.07) after control for body weight. There were no group differences in either the FFST-adjusted cortical bone values at the radius or in the trabecular bone parameters (body weight- or FFST-adjusted) at the tibia and radius.

CONCLUSIONS

Consistent with our adiposity and bone data in late-adolescent white females, our findings in black females entering adulthood also suggest that obesity may adversely influence cortical bone strength.

Bone mineral content and density in obese, overweight, and normal-weighted sedentary adolescent girls

PURPOSE

The aim of this study was to compare the whole body (WB) bone mineral content (BMC) and bone mineral density (BMD) in obese, overweight, and normal-weighted adolescent sedentary girls.

METHODS

This study included 17 obese, 27 overweight, and 21 normal-weighted adolescent (aged, 12-20) sedentary (practicing less than 2 hours of physical activity/week) girls. The three groups (obese, overweight, and normal) were matched for age and maturation index (years since menarche). BMC, bone mineral area (BMA), BMD, and body composition were assessed by dual-energy X-ray asborptiometry. Bone mineral apparent density (BMAD) was calculated for the WB.

RESULTS

Obese girls had higher BMC values than overweight and normal-weighted girls (p < .05 and p < .001, respectively). Overweight girls had higher BMC values than normal-weighted girls (p < .05). BMD values were not different among the three groups. However, obese and overweight girls had lower BMAD and higher BMC/height values in comparison with normal-weighted girls (p < .05). Finally, after adjustment for lean mass, BMC, BMA, BMD, and BMAD were not different among the three groups.

CONCLUSION

In this population, overweight and obesity are associated with higher BMC, BMC/height, and lower BMAD of the WB. This study suggests that BMD, BMC, BMA, and BMAD of the WB are not significantly different among the three groups (obese, overweight, and normal) after adjustment for lean mass. Therefore, our results suggest that the skeleton of the overweight and the obese girls adapts to the increased lean mass.

Lower bone mass in prepubertal overweight children with prediabetes

Childhood studies of the fat-bone relationship are conflicting, possibly reflecting the influence of metabolic abnormalities in some but not all obese children. Bone mass was compared between prepubertal overweight children with (n = 41) and without (n = 99) prediabetes. Associations of bone mass with measures of total and central adiposity, glucose intolerance, insulin sensitivity, lipid profile, systemic inflammation, and osteocalcin also were determined. In 140 overweight children aged 7 to 11 years, an oral glucose tolerance test was used to identify those with prediabetes and for determination of glucose, 2-hour glucose, glucose area under the curve (AUC), insulin, 2-hour insulin, and insulin AUC. Blood samples also were assessed for lipids, C-reactive protein, and osteocalcin. Total-body bone mineral content (BMC), fat-free soft tissue mass (FFST), and fat mass (FM) were measured by dual-energy X-ray absorptiometry (DXA). Visceral adipose tissue (VAT) and subcutaneous abdominal adipose tissue (SAAT) were assessed using MRI. Total-body BMC was 4% lower in overweight children with prediabetes than in those without prediabetes after controlling for sex, race, height, and weight (p = .03). In the total sample, FM was positively related with BMC (β = 0.16, p = .01) after adjusting for sex, race, height, and FFST. However, VAT (β = -0.13, p = .03) and SAAT (β = -0.34, p = .02) were inversely associated with BMC after controlling for sex, race, height, FFST, FM, and SAAT or VAT. No significant associations were found between BMC and the biochemical measurements. Prepubertal overweight children with prediabetes may be at risk for poor skeletal development. In addition, it appears that greater levels of central rather than total adiposity may be deleterious for developing bone.

Femoral neck geometry in overweight and normal weight adolescent girls

Being overweight is associated with increased bone mineral content, bone mineral density (BMD), and bone strength in adults. However, the effect of being overweight on bone strength during adolescence is poorly understood. The aim of this study was to compare femoral neck geometry in overweight and normal weight adolescent girls. This study included 22 overweight (BMI > 25 kg/m(2)) adolescent girls (15.4 +/- 2.4 years old) and 20 maturation-matched (15.2 +/- 1.9 years old) controls (BMI < 25 kg/m(2)). Body composition and BMD were assessed by dual-energy X-ray absorptiometry (DXA). To evaluate bone geometry, DXA scans were analyzed at the femoral neck by the hip structure analysis (HSA) program. Cross-sectional area (CSA), an index of axial compression strength, section modulus (Z), an index of bending strength, cross-sectional moment of inertia (CSMI), cortical thickness (CT), and buckling ratio (BR) were measured from bone mass profiles. Lean mass, body weight, fat mass, and BMI were higher in overweight girls compared to controls (P < 0.001). CSA, Z, and CSMI were higher in overweight girls compared to controls (P < 0.05; P < 0.01 and P < 0.01, respectively). CT and BR were not significantly different between the two groups. After adjustment for body weight, lean mass, or fat mass, using a one-way analysis of covariance (ANCOVA), there were no differences between the two groups (overweight and controls) regarding the HSA variables (CSA, Z, CSMI, CT, and BR). In conclusion, this study suggests that overweight adolescent girls have greater indices of bone axial and bending strength in comparison to controls at the femoral neck.

Relationship of total body fat mass to weight-bearing bone volumetric density, geometry, and strength in young girls

Understanding the influence of total body fat mass (TBFM) on bone during the peri-pubertal years is critical for the development of future interventions aimed at improving bone strength and reducing fracture risk. Thus, we evaluated the relationship of TBFM to volumetric bone mineral density (vBMD), geometry, and strength at metaphyseal and diaphyseal sites of the femur and tibia of young girls. Data from 396 girls aged 8-13 years from the "Jump-In: Building Better Bones" study were analyzed. Bone parameters were assessed using peripheral quantitative computed tomography (pQCT) at the 4% and 20% distal femur and 4% and 66% distal tibia of the non-dominant leg. Bone parameters at the 4% sites included trabecular vBMD, periosteal circumference, and bone strength index (BSI), while at the 20% femur and 66% tibia, parameters included cortical vBMD, periosteal circumference, and strength-strain index (SSI). Multiple linear regression analyses were used to assess associations between bone parameters and TBFM, controlling for muscle cross-sectional area (MCSA). Regression analyses were then repeated with maturity, bone length, physical activity, and ethnicity as additional covariates. Analysis of covariance (ANCOVA) was used to compare bone parameters among tertiles of TBFM. In regression models with TBFM and MCSA, associations between TBFM and bone parameters at all sites were not significant. TBFM explained very little variance in all bone parameters (0.2-2.3%). In contrast, MCSA was strongly related (p<0.001) to all bone parameters, except cortical vBMD. The addition of maturity, bone length, physical activity, and ethnicity did not alter the relationship between TBFM and bone parameters. With bone parameters expressed relative to total body mass, ANCOVA showed that all outcomes were significantly (p<0.001) greater in the lowest compared to the middle and highest tertiles of TBFM. Although TBFM is correlated with femur and tibia vBMD, periosteal circumference, and strength in young girls, this relationship is significantly attenuated after adjustment for MCSA. Nevertheless, girls with higher TBFM relative to body mass have markedly diminished vBMD, geometry, and bone strength at metaphyseal and diaphyseal sites of the femur and tibia.

Influence of the weight status on bone mineral content and bone mineral density in a group of Lebanese adolescent girls

AIM

The aim of this study was to determine the influence of being overweight on whole-body (WB) bone mineral content (BMC) and bone mineral density (BMD) in a group of Lebanese adolescent girls.

METHODS

This study included 32 overweight (BMI>25 kg/m2) adolescent girls (15.3+/-2.3 years old) and 24 maturation-matched (15.7+/-1.7 years old) controls (BMI<25 kg/m2). Bone mineral area (BMA), BMC, BMD at the WB and body composition (lean mass and fat mass) were assessed by dual-energy X-ray absorptiometry (DXA). Calculation of the ratio BMC/height and bone mineral apparent density (BMAD) were completed for the WB.

RESULTS

Expressed as crude values, BMA, BMC and the ratio BMC/height were higher in overweight adolescent girls compared to controls. After adjusting for body weight, there were no differences in BMC or in the ratio BMC/height between the two groups. However, BMA was lower in overweight girls compared to controls. After adjusting for either lean mass or fat mass, there were no significant differences between the two groups regarding these variables: BMC, BMA, BMD, BMC/height and BMAD.

CONCLUSION

This study suggests that the positive effect of overweight on BMC is due to body weight. In fact, the difference in BMC between the overweight and the control girls disappears after adjusting for body weight. In contrast, overweight girls have lower BMA compared to controls when values are adjusted to body weight.

Relation of body fat indexes to vitamin D status and deficiency among obese adolescents

BACKGROUND

Data on the relation between vitamin D status and body fat indexes in adolescence are lacking.

OBJECTIVE

The objective was to identify factors associated with vitamin D status and deficiency in obese adolescents to further evaluate the relation of body fat indexes to vitamin D status and deficiency.

DESIGN

Data from 58 obese adolescents were obtained. Visceral adipose tissue (VAT) was measured by computed tomography. Dual-energy X-ray absorptiometry was used to measure total bone mineral content, bone mineral density, body fat mass (FM), and lean mass. Relative measures of body fat were calculated. Blood tests included measurements of 25-hydroxyvitamin D [25(OH)D], parathyroid hormone (PTH), osteocalcin, type I collagen C-telopeptide, hormones, and metabolic factors. Vitamin D deficiency was defined as 25(OH)D < 20 ng/mL. PTH elevation was defined as PTH > 65 ng/mL.

RESULTS

The mean (+/-SD) age of the adolescents was 14.9 +/- 1.4 y; 38 (66%) were female, and 8 (14%) were black. The mean (+/-SD) body mass index (in kg/m(2)) was 36 +/- 5, FM was 40.0 +/- 5.5%, and VAT was 12.4 +/- 4.3%. Seventeen of the adolescents were vitamin D deficient, but none had elevated PTH concentrations. Bone mineral content and bone mineral density were within 2 SDs of national standards. In a multivariate analysis, 25(OH)D decreased by 0.46 +/- 0.22 ng/mL per 1% increment in FM (beta +/- SE, P = 0.05), whereas PTH decreased by 0.78 +/- 0.29 pg/mL per 1% increment in VAT (P = 0.01).

CONCLUSIONS

To the best of our knowledge, our results show for the first time that obese adolescents with 25(OH)D deficiency, but without elevated PTH concentrations, have a bone mass within the range of national standards (+/-2 SD). The findings provide initial evidence that the distribution of fat may be associated with vitamin D status, but this relation may be dependent on metabolic factors. This study was registered at www.clinicaltrials.gov as NCT00209482, NCT00120146.

Volumetric bone mineral density is an important tool when interpreting bone mineralization in healthy children

In adults, it is well known that gender influences bone mass, but studies in children have shown contradictory results. Also, conflicting results have been reported regarding bone mineral density in obese children.

OBJECTIVE

To investigate bone parameters in healthy 8-year-old children and relate them to anthropometry and self-reported physical activity (PA).

DESIGN

Bone measurements were performed with dual X-ray absorptiometry in 96 children, and questionnaires were used to assess self-reported PA.

RESULTS

Bone mineral content and density differed by gender. Eighteen percent of the children were overweight/obese and they had higher bone mineral content and density than children with normal weight. Bone mineral apparent density (g/cm(3)) of the lumbar spine did not differ, since the vertebral size differed, as was also the case between genders. Self-reported weight-bearing PA influenced bone mass in the hip.

CONCLUSION

PA influenced bone mineralization at this age. The differences in bone mineral content and density in healthy children would mainly be explained by the differences in bone size, reflected in body height and the width of the vertebrae. This indicates the importance of determining volumetric bone mineralization in children.

Bone structure and volumetric BMD in overweight children: a longitudinal study

The effect of excess body fat on bone strength accrual is not well understood. Therefore, we assessed bone measures in healthy weight (HW) and overweight (OW) children. Children (9-11 yr) were classified as HW (n = 302) or OW (n = 143) based on body mass index. We assessed total (ToD) and cortical (CoD) volumetric BMD and bone area, estimates of bone strength (bone strength index [BSI]; stress-strain index [SSIp]), and muscle cross-sectional area (CSA) at the distal (8%), midshaft (50%), and proximal (66%) tibia by pQCT. We used analysis of covariance to compare bone outcomes at baseline and change over 16 mo. At baseline, all bone measures were significantly greater in OW compared with HW children (+4-15%; p <or= 0.001), with the exception of CoD at the 50% and 66% sites. Over 16 mo, ToA increased more in the OW children, whereas there was no difference for change in BSI or ToD between groups at the distal tibia. At the tibial midshaft, SSIp was similar between groups at baseline when adjusted for muscle CSA, but low when adjusted for body fat in the OW group. At both sites, bone strength increased more in OW because of a greater increase in bone area. Changes in SSIp were associated with changes in lean mass (r = 0.70, p < 0.001) but not fat mass. In conclusion, although OW children seem to be at an advantage in terms of absolute bone strength, bone strength did not adapt to excess body fat. Rather, bone strength was adapted to the greater muscle area in OW children.

Bone mineral density in prepubertal obese and control children: relation to body weight, lean mass, and fat mass

The aim of the study was to determine the influence of obesity on bone status in prepubertal children. This study included 20 obese prepubertal children (10.7 +/- 1.2 years old) and 23 maturation-matched controls (10.9 +/- 1.1 years old). Bone mineral area, bone mineral content (BMC), bone mineral density (BMD), and calculation of bone mineral apparent density (BMAD) at the whole body and lumbar spine (L1-L4) and body composition (lean mass and fat mass) were assessed by DXA. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) at the calcaneus were measured with a BUA imaging device. Expressed as crude values, DXA measurements of BMD at all bone sites and BUA (69.30 versus 59.63 dB/MHz, P < 0.01) were higher in obese children. After adjustment for body weight and lean mass, obese children displayed lower values of whole-body BMD (0.88 versus 0.96 g/cm2, P < 0.05) and BMC (1190.98 versus 1510.24 g, P < 0.01) in comparison to controls. When results were adjusted for fat mass, there was no statistical difference between obese and control children for DXA and ultrasound results. Moreover, whole-body BMAD was lower (0.086 versus 0.099 g/cm3, P < 0.0001), whereas lumbar spine BMAD was greater (0.117 versus 0.100 g/cm3, P < 0.001) in obese children. Thus, it was observed that, in obese children, cortical and trabecular bone displayed different adaptation patterns to their higher body weight. Cortical bone seems to enhance both size and BMC and trabecular bone to enhance BMC. Finally, considering total body weight and lean mass of obese children, these skeletal responses were not sufficient to compensate for the excess load on the whole body.

Is adiposity advantageous for bone strength? A peripheral quantitative computed tomography study in late adolescent females

BACKGROUND

Whereas excess adiposity is presumed to be advantageous for the skeleton, studies investigating relations between bone strength and fat during youth have been equivocal.

OBJECTIVES

Relations of percentage body fat (BF) and bone strength indexes were assessed in late adolescent females, taking into consideration surrogates of muscle force [ie, muscle cross-sectional area (MCSA) and bone length]. Bone measurements in the normal- and high-fat groups were also compared.

DESIGN

Late adolescent females (n = 115; aged 18.2 +/- 0.4 y) participated in this cross-sectional study. Fat-free soft tissue mass, fat mass, and percentage BF were measured with the use of dual-energy X-ray absorptiometry. Tibial and radial peripheral quantitative computed tomography measurements were taken at the 4% (trabecular bone), 20% (cortical bone), and 66% (for measurement of MCSA) sites from the distal metaphyses.

RESULTS

Percentage BF was inversely related to radial cortical bone area, total bone cross-sectional area (CSA), cortical bone mineral content (BMC), periosteal circumference, and strength-strain index (SSI) (20% site; all P < 0.05). After control for MCSA and limb length, negative relations remained between percentage BF and radial measurements and were also observed at the tibia (20% site). Unadjusted bone measures were not different between groups. After control for MCSA, the high- compared with the normal-fat group had lower bone measures at the 20% site (cortical bone area and cortical BMC at the tibia, total bone CSA at the radius, and SSI at both the tibia and radius; P < 0.05 for all).

CONCLUSION

Excess weight in the form of fat mass does not provide additional benefits, and may potentially be negative, for adolescent bone.

Racial differences in the association of subcutaneous and visceral fat on bone mineral content in prepubertal children

Total fat mass plays a significant role in determining bone mass, but the specific role of central adiposity independent of total fat mass has not been widely studied. Prepubertal (Tanner 1) children (n = 181; 65 boys, 116 girls, 7.8 +/- 1.5 years), including 99 Caucasians and 82 African Americans from Birmingham, Alabama, participated in this study. Body composition, including total body and trunk fat mass, and bone mineral content (BMC) were measured using dual-energy X-ray absorptiometry. Subcutaneous abdominal adipose tissue (SAAT) and intra-abdominal adipose tissue (IAAT) were determined by single-slice computed tomography (CT). After adjusting for gender, age, height, total fat, and lean mass, trunk weight was inversely correlated with BMC in Caucasians (r = -0.56, P < 0.0001) and in African Americans (r = -0.37, P < 0.05). In Caucasians, independent of gender, age, height, total fat, and lean mass, there was an inverse correlation between SAAT and BMC (r = -0.58, P < 0.0001) but no significant correlation between IAAT and BMC; in addition, SAAT explained 6% of the variance in BMC. In contrast, in African Americans, SAAT and BMC were not significantly correlated. However, while adjusting for gender, age, height, SAAT, total fat, and lean mass, an inverse association between IAAT and BMC was observed in African Americans (r = -0.50, P < 0.01); IAAT also explained 3% of the variance in BMC. These findings suggest that, in general, total abdominal weight is negatively associated with bone mass, but there appear to be racial differences with regard to the contributions of subcutaneous and visceral fat to BMC in prepubertal children.

Sex difference in the effect of puberty on the relationship between fat mass and bone mass in 926 healthy subjects, 6 to 18 years old

OBJECTIVE

Understanding factors influencing bone mineral accrual is critical to optimize peak bone mass during childhood. The epidemic of pediatric obesity and reported higher incident of fracture risk in obese children led us to study the influence of fat mass on bone mineral content (BMC) in children.

RESEARCH METHODS AND PROCEDURES

Height; weight; pubertal stage; and BMC, non-bone fat-free mass (nbFFM), and fat mass (FM) by DXA were obtained in a multiethnic group of healthy children (444 girls/482 boys; 6 to 18 years old) recruited in the New York metropolitan area. Regression techniques were used to explore the relationship between BMC and FM, with age, height, nbFFM, pubertal stage, sex, and ethnicity as covariates.

RESULTS

Because there were significant sex interactions, separate regression analyses were performed for girls and boys. Although ln(nbFFM) was the greatest predictor of ln(BMC), ln(FM) was also a significant predictor in prepubertal boys and all girls but not in pubertal boys. This effect was independent of ethnicity.

DISCUSSION

FM was a determinant of BMC in all girls but in only prepubertal boys. Our study confirms nbFFM as the greatest predictor of BMC but is the first to find a sex difference in the effect of puberty on the relationship of FM to BMC. Our results suggest that, in two individuals of the same sex and weight, the one with greater fat mass will have lower BMC, especially pubertal boys. The implications of these findings for achievement of optimal peak bone mass in a pediatric population with an unprecedented incidence of overweight and "overfat" status remain to be seen.

Hormonal and metabolic consequences of childhood obesity

It is apparent that chronic illnesses such as type 2 diabetes and cardiovascular disease originate in childhood. Obesity in childhood and adolescence hastens their development, enhances their rates of progression, increases the risks of severe complications, and if persistent, reduces life expectancy.

(n-3) fatty acids reduce the release of prostaglandin E2 from bone but do not affect bone mass in obese (fa/fa) and lean Zucker rats

Childhood obesity is prevalent and linked to the development of Type 2 diabetes mellitus (DM) and poor bone health. Some PUFA enhance bone mass and thus may improve bone health in obese children. The study objective was to determine the effects of dietary (n-6) compared with (n-3) essential PUFA and long-chain PUFA (LCPUFA) on bone in an obese and insulin-resistant state. Male fa/fa (n = 48) and lean Zucker rats (n = 48) were fed diets containing safflower oil [SO, high (n-6) PUFA], flaxseed oil [FXO, high (n-3) PUFA], or menhaden oil [MO, high (n-3) LCPUFA] for 9 wk. Measurements included the following: femur bone area (BA), mineral content (BMC), density (BMD), morphometry and ex vivo release of prostaglandin E(2) (PGE(2)); plasma osteocalcin and C-terminal telopeptides of type I collagen. Differences among groups were detected using 2-way ANOVA. Genotype effects in the fa/fa rats included lower femoral weight, length, BA, and BMC, as well as femoral head and proximal epiphysis widths compared with the lean rats, but BMD was not affected. Femur BA, BMC, and BMD did not differ among the dietary groups, but diaphysis width was elevated in the MO group and PGE(2) release was reduced by the FXO and MO diets. No genotype x diet interactions were observed. These data indicate that the fa/fa Zucker rat is at risk for low bone mass and that dietary (n-3) FA effectively reduce PGE(2) release. Whether reduced PGE(2) will support optimal peak bone mass during childhood and conserve bone mass with aging warrants investigation.

Proximal femur bone geometry is appropriately adapted to lean mass in overweight children and adolescents

It is unclear if the bones of overweight children are appropriately adapted to increased loads. The objective of this study was to compare bone geometry in 40 overweight (body mass index [BMI] > 85th percentile) and 94 healthy weight (BMI < or = 85th percentile) subjects, ages 4-20 years. Dual energy X-ray absorptiometry (Hologic QDR 2000) scans were analyzed at the femoral shaft (FS) and narrow neck (NN) by the Hip Structure Analysis program. Subperiosteal width, cortical thickness and indices of bone axial and bending strength (bone cross-sectional area [CSA] and section modulus [Z]) were measured from bone mass profiles. Multivariate regression models were used to compare overweight and healthy weight subjects. Z was 11 (95% CI 5, 19) and 13 (7, 20) percent higher at the FS and NN, respectively, in overweight subjects (P < 0.001), adjusted for height, maturation and gender. At the NN, higher Z was due to greater subperiosteal width [4% (2, 7)] and bone CSA [10% (5, 16]) and at the FS, to higher bone CSA [10% (5, 16)] and thicker cortices [9% (3, 15)]. When lean mass was added to the models, bone variables did not differ between overweight and healthy weight subjects (P > 0.22), with the exception of NN subperiosteal width [3% (0, 6), P = 0.04]. Fat mass did not contribute significantly to any model. In summary, proximal femur bone geometric strength in overweight children was appropriately adapted to lean mass and height but greater weight in the form of fat mass did not have an independent effect on bone bending strength. These geometric adaptations are consistent with the mechanostat hypothesis that bone strength adapts primarily to muscle forces, not to static loads represented by body weight.