Overweight and obese children have low bone mass and area for their weight

Factors associated with bone turnover and speed of sound in early and late-pubertal females

This cross-sectional study examines whether maturity, body composition, physical activity, dietary intake, and hormonal concentrations are related to markers of bone turnover and tibial speed of sound (tSOS) in premenarcheal (n = 20, 10.1 ± 1.1 years) and postmenarcheal girls (n = 28, aged 15.0 ± 1.4 years). Somatic maturity was evaluated using years from age of peak height velocity (aPHV). Daily dietary intake was assessed with a 24-h recall interview, and moderate to very vigorous physical activity (MVPA) was measured using accelerometry. Plasma levels of 25-OH vitamin D, serum levels of insulin-like growth-factor 1 (IGF-1) and leptin, and serum levels of bone turnover markers including osteocalcin (OC), bone-specific alkaline phosphatase (BAP) and cross-linked N-teleopeptide of type I collagen (NTX) were measured using ELISA. OC, BAP, and NTX were significantly higher while IGF-1 and tSOS were lower in the premenarcheal group. The premenarcheal girls were more active and had higher daily energy intake relative to their body mass but there were no group differences in body mass index percentile. Maturity predicted 40%-57% of the variance in bone turnover markers. Additionally, daily energy intake was a significant predictor of OC, especially in the postmenarcheal group. IGF-1 and MVPA were significant predictors of BAP in the group as a whole. However, examined separately, IGF-1 was a predictor of BAP in the premenarcheal group while MVPA was a predictor in the postmenarcheal group. Adiposity and leptin were both negative predictors of tSOS, with leptin being specifically predictive in the postmenarcheal group. In conclusion, while maturity was the strongest predictor of bone markers and tSOS, dietary intake, physical activity, body composition, and hormonal factors further contribute to the variance in bone turnover and bone SOS in young Caucasian females. Further, the predicting factors of bone turnover and tSOS were different within each maturity group.

The role of bone shape in determining gender differences in vertebral bone mass

Dual-energy X-ray absorptiometry (DXA) measures of bone mineral density (BMD) in children fail to account for growth because bone depth is unmeasured. While multiple adjustment methods have been proposed using body or bone size, the effect of vertebral shape is relatively unknown. Our study aimed to determine gender differences in vertebral shape and their impact on areal BMD (aBMD). We recruited 189 children, including 107 boys, aged 4-17 years, who attended the emergency department due to trauma. None had fractured. Height, weight, Tanner stage, and DXA measurements of the lumbar spine (LS) and total body were obtained. Cylindrical models were used to predict relationships between vertebral width (VW) and areal density for a given vertebral area assuming uniform volumetric density. The actual relationships between VW, bone area, and aBMD for the LS in the children were then determined. The theoretical models predicted a positive relationship between width and areal density for a constant vertebral area. Actual vertebral measurements demonstrated that boys had greater VW for a given vertebral area but lower aBMD for a given VW than girls at any age. The most likely explanation for the apparent paradox was that vertebral cortical thickness relative to width was greater in girls. This difference remained after adjusting for lean mass, suggesting that bone's response to mechanical stimulation may vary between the sexes during growth with consequent evolutionary advantage for girls approaching reproductive age.

Pediatric obesity: a review for the child psychiatrist

Child and adolescent psychiatrists frequently encounter children who are obese in their practices and may be asked to work alongside primary care physicians and other specialists who treat youngsters with obesity. To offer expert consultation, they must understand all aspects of the pediatric obesity epidemic. By summarizing the relevant endocrinology, cardiology, nutrition, exercise science, and public health literature, this review of pediatric obesity assesses the epidemic's background, delineates the challenges of clinical care, and appraises the therapeutic recommendations for this population of patients and their families.

Longitudinal changes in calcaneal quantitative ultrasound measures during childhood

This longitudinal study examined how calcaneal quantitative ultrasound (QUS) measures change during childhood while taking into account skeletal maturation, body mass index (BMI), and physical activity. The study reported sex differences in QUS growth curves and an inverse relationship between BMI and speed of sound (SOS) measures.

INTRODUCTION

The aim of this study was to examine how calcaneal QUS parameters change over time during childhood and to determine what factors influence these changes.

METHODS

The study sample consisted of a total of 192 Caucasian children participating in the Fels Longitudinal Study. A total of 548 calcaneal broadband ultrasound attenuation (BUA) and SOS observations were obtained between the ages of 7.6 and 18 years. The best fitting growth curves were determined using statistical methods for linear mixed effect models.

RESULTS

There are significant sex differences in the pattern of change in QUS parameters (p < 0.05). The relationship between QUS measures and skeletal age is best described by a cubic growth curve in boys and a linear pattern among girls. Boys experience their most rapid growth in BUA and SOS in early and late adolescence, while girls experience constant growth throughout childhood. Adiposity levels were significantly associated with the changes in SOS among boys (p < 0.001) and girls (p < 0.01), indicating that children with higher BMI are likely to have lower SOS over time compared to children with lower BMI. For girls, physical activity levels showed positive associations with changes in QUS measures (p < 0.05).

CONCLUSION

This study documents significant sex differences in the pattern of change in QUS measures over childhood and adolescence. Our study also shows significant influences of adiposity and physical activity on the pattern of change in QUS measures during childhood.

Correlation of insulin sensitivity with bone mineral status in obese adolescents with nonalcoholic fatty liver disease

AIM

The aim of this study was to investigate the relationships between bone mineral density (BMD) vs insulin resistance and metabolic risk factors in obese adolescents with nonalcoholic fatty liver disease (NAFLD).

PATIENTS AND METHODS

Eighty-two obese adolescents [45 girls and 37 boys, mean age: 12·3 ± 1·7 years, mean body mass index-standard deviation score (BMI-SDS): 1·9 ± 0·2] and 30 control subjects (15 girls and 15 boys, mean age: 12·3 ± 1·45 years, mean BMI-SDS: 0·5 ± 0·7) were enrolled the study. The obese subjects were divided into two groups based on the presence or absence of liver steatosis with high transaminases (NAFLD group and non-NAFLD group). Insulin resistance was evaluated by homeostasis model assessment (HOMA-IR) from fasting samples. BMD was determined by dual-energy X-ray absorptiometry.

RESULTS

Fasting insulin levels in the NAFLD group were significantly higher than in the non-NAFLD obese (32·3 ± 24·0 vs 11·02 ± 2·95 mU/l, P < 0·001) and control groups (8·4 ± 2·4 mU/l, P< 0·001). The NAFLD group had higher values of HOMA-IR than the non-NAFLD obese (7·3 ± 0·1 vs 2·3 ± 0·7, P < 0·001) and control groups (1·8 ± 0·5, P < 0·001). BMD-SDS measurements were lower in the NAFLD group than in the non-NAFLD (0·56 ± 0·3 vs 1·02 ± 0·9, P < 0·001) and control groups (0·56 ± 0·3 vs 1·37 ± 1·04, P < 0·001). BMD-SDS was positively correlated with BMI-SDS (r = 0·530, P = 0·004) and negatively correlated with HOMA-IR (r = -0·628, P = 0·017) in the NAFLD obese group.

CONCLUSION

This study reports the association between BMD-SDS and insulin resistance in obese adolescents both with and without NAFLD, although the NAFLD group had a lower BMD-SDS than the non-NAFLD group. We suggest that NAFLD has a detrimental effect on bone health in adolescents, and it is correlated with increased insulin resistance.

Obesity augments calcium-induced increases in skeletal calcium retention in adolescents

CONTEXT

Overweight adolescents have low bone mineral content for weight and are at increased risk for fractures.

OBJECTIVE

The aim was to determine whether overweight and obesity influence the positive relationship between dietary calcium intake and skeletal calcium retention in adolescents.

DESIGN

Analysis of pooled data from calcium balance studies in adolescents.

SETTING

Participants each underwent a 3-wk calcium balance study in a controlled environment.

PARTICIPANTS

Participants included 280 White, Black, and Asian boys (n = 73) and girls (n = 207) ages 10-16 yr.

MAIN OUTCOME MEASURE

The relationship among body mass index (BMI), calcium intake, and calcium retention was modeled using linear regression.

RESULTS

Calcium intake, BMI, sex, race, and age explained 27.9% of the variation in calcium retention. At low calcium intakes, there was no effect of BMI on skeletal calcium retention, but at higher calcium intakes, BMI increased skeletal calcium retention.

CONCLUSIONS

Greater gains in calcium retention occur with increases in calcium intake in adolescents with higher BMI compared with those with lower BMI. Additional studies are needed to investigate whether increasing calcium intake reduces the increased risk of fracture associated with overweight and obesity in adolescents.

Effects of obesity on bone metabolism

Obesity is traditionally viewed to be beneficial to bone health because of well-established positive effect of mechanical loading conferred by body weight on bone formation, despite being a risk factor for many other chronic health disorders. Although body mass has a positive effect on bone formation, whether the mass derived from an obesity condition or excessive fat accumulation is beneficial to bone remains controversial. The underline pathophysiological relationship between obesity and bone is complex and continues to be an active research area. Recent data from epidemiological and animal studies strongly support that fat accumulation is detrimental to bone mass. To our knowledge, obesity possibly affects bone metabolism through several mechanisms. Because both adipocytes and osteoblasts are derived from a common multipotential mesenchymal stem cell, obesity may increase adipocyte differentiation and fat accumulation while decrease osteoblast differentiation and bone formation. Obesity is associated with chronic inflammation. The increased circulating and tissue proinflammatory cytokines in obesity may promote osteoclast activity and bone resorption through modifying the receptor activator of NF-κB (RANK)/RANK ligand/osteoprotegerin pathway. Furthermore, the excessive secretion of leptin and/or decreased production of adiponectin by adipocytes in obesity may either directly affect bone formation or indirectly affect bone resorption through up-regulated proinflammatory cytokine production. Finally, high-fat intake may interfere with intestinal calcium absorption and therefore decrease calcium availability for bone formation. Unraveling the relationship between fat and bone metabolism at molecular level may help us to develop therapeutic agents to prevent or treat both obesity and osteoporosis. Obesity, defined as having a body mass index ≥ 30 kg/m2, is a condition in which excessive body fat accumulates to a degree that adversely affects health. The rates of obesity rates have doubled since 1980 and as of 2007, 33% of men and 35% of women in the US are obese. Obesity is positively associated to many chronic disorders such as hypertension, dyslipidemia, type 2 diabetes mellitus, coronary heart disease, and certain cancers. It is estimated that the direct medical cost associated with obesity in the United States is ~$100 billion per year.Bone mass and strength decrease during adulthood, especially in women after menopause. These changes can culminate in osteoporosis, a disease characterized by low bone mass and microarchitectural deterioration resulting in increased bone fracture risk. It is estimated that there are about 10 million Americans over the age of 50 who have osteoporosis while another 34 million people are at risk of developing the disease. In 2001, osteoporosis alone accounted for some $17 billion in direct annual healthcare expenditure. Several lines of evidence suggest that obesity and bone metabolism are interrelated. First, both osteoblasts (bone forming cells) and adipocytes (energy storing cells) are derived from a common mesenchymal stem cell and agents inhibiting adipogenesis stimulated osteoblast differentiation and vice versa, those inhibiting osteoblastogenesis increased adipogenesis. Second, decreased bone marrow osteoblastogenesis with aging is usually accompanied with increased marrow adipogenesis. Third, chronic use of steroid hormone, such as glucocorticoid, results in obesity accompanied by rapid bone loss. Fourth, both obesity and osteoporosis are associated with elevated oxidative stress and increased production of proinflammatory cytokines. At present, the mechanisms for the effects of obesity on bone metabolism are not well defined and will be the focus of this review.

Effects of obesity on the biomechanics of stair-walking in children

Anthropometric characteristics, particularly body mass, are important factors in the development and progression of varus/valgus angular deformities of the knee and have long-term implications including increased risk of osteoarthritis. However, information on how excessive body weight affects the biomechanics of dynamic activities in children is limited. The purpose of this study was to test the hypothesis that during stair-walking lower extremity joint moments normalized to body mass in obese children are greater than those in normal-weight children. Eighteen obese children (10.5±1.5 years, 148±10cm, 56.6±8.4kg) and 17 normal-weight children (10.4±1.3 years, 143±9cm, 36.7±7.5kg) were recruited. A Vicon system and two AMTI force plates were used to record and analyze the kinematics and kinetics of ascending and descending stairs. Significant differences in spatio-temporal, kinematic and kinetic parameters during ascending and descending stairs between obese and normal-weight children were detected. For stair ascent, greater hip abduction moments (+23%; p=0.001) and greater knee extension moments (+20%; p=0.008) were observed. For stair descent, smaller hip extension moment (-52%; p=0.031), and greater hip flexion moments (+25%; p=0.016) and knee extension moments (+15%, p=0.008) were observed for obese subjects. To date, it is unclear if and how the body may adapt to greater joint moments in obese children. Nevertheless, these differences in joint moments may contribute to a cumulative overloading of the joint through adolescence into adulthood, and potentially result in a greater risk of developing knee and hip osteoarthritis.

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.

Gender differences in bone mineral density in obese children during pubertal development

OBJECTIVE

To investigate whether body mass index (BMI) and body composition can affect peak bone mass in a population of obese (OB) (BMI SDS>2.0) and normal weight (NORM) (BMI-SD score <2.0) pubertal subjects (Tanner stage T3 to T5).

PATIENTS AND METHODS

151 subjects (81 OB, age 14.5±2.4 yr) were analyzed using dual-X-ray absorbiometry technique to study Lumbar and whole body bone mineral density (BMD) (areal, normalized for height) and Z-score, lean mass (LM) and lean/fat ratio.

RESULTS

As a whole group, OB males did not show any significant difference in bone parameters vs NORM, while OB females showed higher bone density parameters (p<0.05). When grouped according to T, while OB males showed higher bone density at T3-4 stage (p<0.01), and lower at T5 (p<0.01) compared to NORM, OB females showed a tendency through increased BMD at T3-4 and T5 although statistically different only at T5. BMD was independently correlated to LM, lean/fat ratio, and testosterone in NORM males and, at lower level, in OB males, while to LM in NORM females and only to age in OB females.

CONCLUSION

Our data seem to confirm the possible negative influence of obesity on bone density in boys, a possible explanation could be an unfavorable body composition during sexual maturation that seems not to affect bone development in adolescents girls.

Are extremity musculoskeletal injuries in children related to obesity and social status? A prospective observational study in a district general hospital

BACKGROUND

Obesity is one of the several independent risk factors for the risk of fractures. Major epidemiological studies also suggested the social status of the patients to be a confounding factor. We aimed to look at the influence of obesity on fractures and to determine if the social status of the patients is a confounding factor.

METHODS

This is an observational study of 560 children with musculoskeletal injuries who presented over a period of 8 months and the data were collected prospectively. Obesity status and social deprivation index were estimated.

RESULTS

The prevalence of overweight and obese children was 29.9%. Twenty-four percent of the boys and 31% of the girls were obese (P = 0.2). In the group of most deprived areas, the prevalence of obesity increased to 40% in those needing admission for intervention.

CONCLUSIONS

Although there is a slight increase in obesity, there is no suggestion of increased rate of fractures in deprived areas. Upper limb injuries were more predominant, with distal radius fracture being the most common injury. Boys sustain fractures twice as often as girls. There is a tendency to increasing obesity with increasing age.

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.

Forearm fractures in children and bone health

PURPOSE OF REVIEW

Summary highlighting the evidence that bone health may affect forearm fracture risk in children.

RECENT FINDINGS

Although the incidence of other fractures and injuries are decreasing, the incidence of forearm fractures is increasing in otherwise healthy children. There is a growing volume of research that forearm fracture risk in children may be related to deficiencies in parameters of bone health. Available evidence of this relationship was summarized and included direct links to bone health (measurement of bone properties), indirect links to bone health (diet, vitamin D status, BMI), and genetic analyses.

SUMMARY

There is consistent and convincing evidence of an association between bone mineral density and forearm fracture risk in children. Studies of calcium intake and supplementation are less extensive in scope but suggest that effects of calcium deficiency on the radius may contribute to childhood forearm fracture risk. Forearm fracture risk in obese children is likely to reflect a combination of suboptimal bone health status and behavioral characteristics. Published data on the role of vitamin D status and genetic factors are limited but merit further consideration. Further investigation is needed to better understand the factors contributing to forearm fracture risk in children and translate this knowledge into effective clinical prevention and practice.

Relative importance of body composition, osteoporosis-related behaviors, and parental income on bone speed of sound in adolescent females

INTRODUCTION

Adolescence provides a unique opportunity to employ strategies aimed at optimizing peak bone mass yet there are limited studies on the relationship between specific social constructs, osteoporosis-related behaviors, and bone health status in adolescent females. The purpose of this study was to examine associations between bone speed of sound (SOS) and body composition, osteoporosis-related health behaviors, and parental income in adolescent females.

METHODS

Four hundred forty-two female students in grades 9-12 from schools in Southern Ontario, Canada were measured for height, body mass, and percent body fat and completed a battery of instruments to assess osteoporosis-related health behaviors. Bone SOS was measured by transaxial quantitative ultrasound at the distal radius and midtibia.

RESULTS

Percent body fat was a negative correlate of tibial SOS. No significant correlation was found between physical activity and bone SOS yet physical activity was negatively related to adiposity. Hierarchical regression showed that age and percent body fat were the most important predictors of the variance in tibial SOS scores, with calcium intake having a weaker, yet significant, relationship. Age was the only statistically significant predictor of radial SOS. Users of oral contraceptives had higher radial SOS when controlling for age. Higher parental income was not associated with bone SOS but positive associations between parental income, daily calcium intake, and weekly physical activity were noted.

CONCLUSIONS

Bone SOS is reduced in adolescent females with increased adiposity, whereas it is positively influenced by oral contraceptives and daily calcium intake.

Fat mass accumulation compromises bone adaptation to load in Finnish women: a cross-sectional study spanning three generations

Body weight and lean mass correlate with bone mass, but the relationship between fat mass and bone remains elusive. The study population consisted of 396 girls and 138 premenopausal mothers and 114 postmenopausal grandmothers of these girls. Body composition and tibial length were assessed using dual-energy X-ray absorptiometry (DXA), and bone traits were determined at the tibia using peripheral quantitative computed tomography (pQCT) in the girls at the ages of 11.2 ± 0.8, 13.2 ± 0.9, and 18.3 ± 1.0 years and in the mothers (44.7 ± 4.1 years) and grandmothers (70.7 ± 6.3 years). The values of relative bone strength index (RBSI), an index reflecting the ratio of bone strength to the load applied on the tibia, were correlated among family members (all p < .05). The mean values of RBSI were similar among 11- and 18-year-old girls and premenopausal women but significantly lower in 13-year-old girls and postmenopausal women. However, in each age group, subjects in the highest BMI tertiles had the lowest RBSI values (all p < .01). RBSI was inversely associated with body weight (all p < .01), indicating a deficit in bone strength relative to the applied load from greater body weight. RBSI was inversely associated with fat mass (all p < .001) across age groups and generations but remained relatively constant with increasing lean mass in girls and premenopausal women (all p > .05), indicating that the bone-strength deficit was attributable to increased fat mass, not lean mass. Moreover, the adverse effect of fat mass was age-dependent, with every unit increase in fat mass associated with a greater decrease in RBSI in pre- and postmenopausal women than in girls (all p < .001). This is largely due to the different capacity of young and adult bones to increase diaphyseal width by periosteal apposition in response to increased load. In summary, increasing body weight with fat accumulation is accompanied by an age-dependent relative bone-strength deficit in women because the beneficial effects of increased fat mass on bone, if any, do not compensate for the mechanical burden that it imposes.

Bone and body segment lengthening and widening: a 7-year follow-up study in pubertal girls

During growth bone increases in length and width as does the body size. The aim of this paper was to examine the growth pattern of body height and weight, and the width and length of various body segments, and to establish the timing of peak growth velocity (PV) in relation to time of menarche in a cohort of Finnish girls followed from age 10 until 18. The study was a 7-year longitudinal cohort study. Widths and lengths of body segments and bones were measured from DXA scan images using bone landmarks in 396 girls aged 10 to 13 years at baseline, and in 255 mothers and 159 grandmothers. The girls' growth velocities (rate of change with time) peaked at 13.5 months prior to menarche for height, 14.4 months for weight, and 15.4 months for BMI. Shoulder width peaked at 18.2 months, lesser pelvis width at 13.5 months and greater pelvis width at 11.6 months prior to menarche. The PV of various body segment lengths showed that the femur peaked earliest at 20.7 months prior to menarche, followed by the humerus (at 18.0 months), radius (at 17.4 months), tibia (at 17.5 months), and trunk (at 11.8 months), respectively. All the long bones were linearly correlated with height while the flat and irregular bones had a nonlinear growth relationship with height (r(2)=0.73-0.88). By the age of 18 years the girls had reached their mothers' height (101%) and humerus, radius, femur and tibia lengths (100-101%), but not their mothers' shoulder, great pelvis and lesser pelvis widths (98%, 95% and 93%, respectively). Our data confirmed that, after bone elongation had ceased, segment width continued to increase, although at a slower speed, into early adulthood. The wide variations in growth velocity of these anthropomorphic measurements underscore the need to optimize nutrition and physical activity from early puberty onward in order to maximize bone development.

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.

Caloric restriction leads to high marrow adiposity and low bone mass in growing mice

The effects of caloric restriction (CR) on the skeleton are well studied in adult rodents and include lower cortical bone mass but higher trabecular bone volume. Much less is known about how CR affects bone mass in young, rapidly growing animals. This is an important problem because low caloric intake during skeletal acquisition in humans, as in anorexia nervosa, is associated with low bone mass, increased fracture risk, and osteoporosis in adulthood. To explore this question, we tested the effect of caloric restriction on bone mass and microarchitecture during rapid skeletal growth in young mice. At 3 weeks of age, we weaned male C57Bl/6J mice onto 30% caloric restriction (10% kcal/fat) or normal diet (10% kcal/fat). Outcomes at 6 (n = 4/group) and 12 weeks of age (n = 8/group) included body mass, femur length, serum leptin and insulin-like growth factor 1 (IGF-1) values, whole-body bone mineral density (WBBMD, g/cm(2)), cortical and trabecular bone architecture at the midshaft and distal femur, bone formation and cellularity, and marrow fat measurement. Compared with the normal diet, CR mice had 52% and 88% lower serum leptin and 33% and 39% lower serum IGF-1 at 6 and 12 weeks of age (p < .05 for all). CR mice were smaller, with lower bone mineral density, trabecular, and cortical bone properties. Bone-formation indices were lower, whereas bone-resorption indices were higher (p < .01 for all) in CR versus normal diet mice. Despite having lower percent of body fat, bone marrow adiposity was elevated dramatically in CR versus normal diet mice (p < .05). Thus we conclude that caloric restriction in young, growing mice is associated with impaired skeletal acquisition, low leptin and IGF-1 levels, and high marrow adiposity. These results support the hypothesis that caloric restriction during rapid skeletal growth is deleterious to cortical and trabecular bone mass and architecture, in contrast to potential skeletal benefits of CR in aging animals.

Percent fat mass is inversely associated with bone mass and hip geometry in rural Chinese adolescents

This study was an attempt to examine the phenotypic, genetic, and environmental correlations between percent fat mass (PFM) and bone parameters, especially hip geometry, among 786 males and 618 females aged 13 to 21 years from a Chinese twin cohort. PFM, bone area (BA), bone mineral content (BMC), cross-sectional area (CSA), and section modulus (SM) were obtained by dual-energy X-ray absorptiometry. Multiple linear regression models were used to assess the PFM-bone relationships. A structural equation model for twin design was used to estimate genetic/environmental influences on individual phenotype and phenotypic correlations. After controlling for body weight and other pertinent covariates, we observed inverse associations between PFM and bone parameters: Compared with the lowest age- and gender-specific tertile of PFM, males in the highest tertile of PFM had lower measures of whole-body-less-head BA (WB-BA), lumbar spine BA (L(2)-L(4)-BA), total-hip BA (TH-BA), total-hip BMC, CSA, and SM (p < .005 for all, adjusted p < .05). Similar inverse associations were observed in females for all the preceding parameters except WB-BA and L2-L(4)-BA. These associations did not vary significantly by Tanner stages. In both genders, the estimated heritabilities were 80% to 86% for BMC, 67% to 80% for BA, 74% to 77% for CSA, and 64% for SM. Both shared genetics and environmental factors contributed to the inverse PFM-bone correlations. We conclude that in this sample of relatively lean Chinese adolescents, at a given body weight, PFM is inversely associated with BA, BMC, and hip geometry in both genders, and such associations are attributed to both shared genetic and environmental factors.

Is childhood obesity associated with bone density and strength in adulthood?

Associations between childhood obesity and adult bone traits were assessed among 62 obese premenopausal women, of which 12 had been obese since childhood (ObC), and 50 had gained excess weight in adulthood (ObA). Body composition and bone mineral content (BMC) of the total body, spine, and proximal femur were assessed with DXA. Total cross-sectional area and cortical (diaphyseal CoD) and trabecular (epiphyseal TrD) bone density of the radius and tibia were measured with pQCT. Compared to ObA-group, ObC-group was 5.2 cm taller having 2.5 and 3.5 kg more lean and fat mass, respectively. Depending on the statistical adjustment, ObC-group had 5-10% greater TrD both in tibia and in radius. The remaining bone traits did not significantly differ between the groups. Current preliminary observations bring up an interesting question whether childhood obesity can result in denser trabecular bone in adulthood. However, prudence must be exercised in the statistical adjustment.

Percent body fat, fractures and risk of osteoporosis in women

OBJECTIVES

Globally, in an aging population, osteoporosis and fractures are emerging as major public health problems; accessible and affordable recognition, prevention and treatment strategies are needed. Percent body fat is known to be associated with bone mineral density and fractures. This paper uses an innovative, virtually cost-free method to estimate percent body fat from age, height and weight, and assesses its validity by examining the association between percent body fat and fractures among women 39 and older.

DESIGN

An epidemiologic study.

PARTICIPANTS

3940 college alumnae, median age 53.6, participated by responding to a mailed questionnaire covering medical history, behavioral factors, birth date, weight and height.

STATISTICAL METHODS

T-tests, chi-square and multivariable logistic regression.

MEASUREMENTS

Percent body fat estimated from age, weight, height and gender.

RESULTS

Associations of fractures with percent body fat are expressed as odds ratios: for osteoporotic (wrist, hip and/or x-ray confirmed vertebral), the adjusted OR = 2.41, 95% CI (1.65, 3.54), P < 0.0001; for wrist fractures, the adjusted OR = 2.56, 95% CI (1.65, 3.96), P < 0.0001; for x-ray confirmed vertebral fractures the adjusted OR = 4.69, 95% CI (2.05, 10.77), P=0.0003).; and for non-osteoporotic, he adjusted OR= 1.00, 95% CI (0.76 1.32), P=0.999.

CONCLUSION

The findings are consistent with methods using DXA and/or other technologies that show percent body fat is associated with fractures of the wrist and vertebrae. Identification of risk factors is necessary for the prevention and treatment of osteoporosis and osteoporotic fractures. Estimation of percent body fat from age, height and weight may be a valid, cost-saving, and cost-effective alternative tool for screening and assessing risk of osteoporosis in settings where Dual x-ray absorptiometry (DXA) or other radiological techniques are too costly or unavailable.

Percentile values for running sprint field tests in children ages 6-17 years: influence of weight status

The aim of this study was to provide percentile values for six different sprint tests in 2,708 Spanish children (1,234 girls) ages 6-17.9 years. We also examined the influence of weight status on sprint performance across age groups, with a focus on underweight and obese groups. We used the 20-m, 30-m, and 50-m running sprint standing start and running start tests to assess sprint performance. We calculated body mass index (BMI) using and categorized participants according to the BMI international cut-off for underweight, normal weight, overweight, and obese. Boys had significantly better scores than girls in all tests, except for the 30-m running sprint standing start and running start tests in the 6-7 year-old group. The underweight group had significantly better scores than their obese counterparts, whereas there were similar levels between underweight and normal weight individuals. The normal weight group showed a significantly better performance than their overweight and obese counterparts. Overweight boys had significantly better performance than their obese counterparts. In conclusion, the percentiles values of six running tests varied by age and gender The findings indicated that underweight youth did not have poorer sprint performance, and the obese group had lower scores than their leaner counterparts.

Pediatric obesity: a review for the child psychiatrist

Child and adolescent psychiatrists frequently encounter children who are obese in their practices and may be asked to work alongside primary care physicians and other specialists who treat youngsters with obesity. To offer expert consultation, they must understand all aspects of the pediatric obesity epidemic. By summarizing the relevant endocrinology, cardiology, nutrition, exercise science, and public health literature, this review of pediatric obesity assesses the epidemic's background, delineates the challenges of clinical care, and appraises the therapeutic recommendations for this population of patients and their families.

Factors associated with bone mineral density and content in 7-year-old children

OBJECTIVE

To evaluate the bone status of 7-year-old school children in Reykjavik, Iceland, and to see if gender, height, lean body mass and fat mass is associated with bone mineral density (BMD) and bone mineral content (BMC) in the lumbar vertebrae and hip.

STUDY DESIGN

A cross-sectional study of a sample of 7-year-old school children.

SETTING

Six elementary schools in Reykjavik, Iceland.

SUBJECTS

All children attending second grade in these six schools were invited to participate. Three hundred twenty-six children were invited and 211 (65%) participated in the study.

MAIN OUTCOME MEASURES

Lean body mass, bone mineral density, bone mineral content and total fat mass.

RESULTS

Both BMD and BMC were positively correlated with sex, height and lean body mass. Fat mass was positively correlated to BMC but not BMD in the total body and lumbar vertebrae. When analyzed with multiple linear regression, the bone area and lean body mass (LBM) were positively associated with BMC in the hip and total body, but total fat mass (TFM) was negatively associated with BMC, the model explaining about 88% of the variance (R2) in the total body bone mineral content (TBMC) and 74% of the variance (R2) in the BMC of the hip. LBM was positively associated with total body bone mineral density (TBMD) but TFM negatively associated. Neither height nor gender contributed to total BMC and BMD in our multiple linear regression models.

CONCLUSION

The study emphasizes that fat mass may play different roles in children and adults and that both LBM and TFM should be taken into consideration when interpreting BMC and BMD for children.

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.

Fat and bone in children: differential effects of obesity on bone size and mass according to fracture history

Fat mass predicts bone accrual in prepubertal children, but obese children have increased fracture risk. We hypothesised that bone size and mass would vary according to prior fracture in obese children. One hundred and three children (52 obese) underwent dual-energy X-ray absorptiometry (DXA) scanning of the lumbar spine, total body, and radial metaphysis and diaphysis. We derived body size-adjusted bone mineral density (BMD) estimates for each site using commonly employed procedures. Following adjustment for either age, age(2) and weight, or height and weight based on a reference group of nonobese controls without previous fracture, obese children with prior fracture showed a 0.8 to 1.2 SD reduction in total body areal BMD (aBMD), a 3.0 SD decrease in lumbar (L2-4) aBMD, and a 2.0 SD reduction in radial shaft aBMD. These changes were significant at p < .005. Lumbar volumetric BMD (vBMD) calculated by Carter and Kröger algorithms was significantly reduced in obese children with prior fracture (2.0 to 3.3 SD). Eighteen percent of obese children fulfilled the criteria for osteoporosis. Despite greater lean mass for height in obese children (p < .0001), total body bone mineral content (BMC) for lean mass was reduced (p = .002). Multiple regression models adjusting for height, weight, and gender demonstrated an inverse relationship between total body fat mass and total body, lumbar, and ultradistal radius BMC and aBMD. The data suggest that fat mass substantially inhibits bone accrual in children with prior fracture. These children may require targeted interventions to increase bone mass during adolescence to achieve optimal peak bone mass and reduce the risk of osteoporosis later in life.

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.

Fat mass exerts a greater effect on cortical bone mass in girls than boys

CONTEXT

It is unclear whether fat mass (FM) and lean mass (LM) differ in the way they influence cortical bone development in boys and girls.

OBJECTIVE

The aim of the study was to investigate the contributions of total body FM and LM to parameters related to cortical bone mass and geometry.

DESIGN/SETTING

We conducted a longitudinal birth cohort study, the Avon Longitudinal Study of Parents and Children.

PARTICIPANTS

A total of 4005 boys and girls (mean age, 15.5 yr) participated in the study.

OUTCOME MEASURES

We measured cortical bone mass, cortical bone mineral content (BMC(C)), cortical bone mineral density, periosteal circumference (PC), and endosteal circumference by tibial peripheral quantitative computed tomography.

RESULTS

LM had a similar positive association with BMC(C) in boys and girls [regression coefficients with 95% confidence interval (CI); P for gender interactions: boys/girls, 0.952 (0.908, 0.997); P = 0.85]. However, the mechanisms by which LM influenced bone mass differed according to gender because LM was positively associated with PC more strongly in girls [boys, 0.579 (0.522, 0.635); girls, 0.799 (0.722, 0.875); P < 0.0001], but was only associated with cortical bone mineral density in boys [boys, 0.443 (0.382, 0.505); girls, 0.014 (-0.070, 0.097); P < 0.0001]. There was a stronger positive association between FM and BMC(C) in girls [boys, 0.227 (0.185, 0.269); girls, 0.355 (0.319, 0.392); P < 0.0001]. This reflected both a greater positive association of FM with PC in girls [boys, 0.213 (0.174, 0.253); girls, 0.312 (0.278, 0.347); P = 0.0002], and a stronger negative association with endosteal circumference(PC) [boys, -0.059 (-0.096, 0.021); girls, -0.181 (-0.215, -0.146); P < 0.0001].

CONCLUSIONS

Whereas LM stimulates the accrual of cortical bone mass to a similar extent in boys and girls, FM is a stronger stimulus for accrual of cortical bone mass in girls, reflecting a greater tendency in females for FM to stimulate periosteal growth and suppress endosteal expansion.

Bone mass and strength in older men with type 2 diabetes: the Osteoporotic Fractures in Men Study

The effects of type 2 diabetes mellitus (T2DM) on bone volumetric density, bone geometry, and estimates of bone strength are not well established. We used peripheral quantitative computed tomography (pQCT) to compare tibial and radial bone volumetric density (vBMD, mg/cm(3)), total (ToA, mm(2)) and cortical (CoA, mm(2)) bone area and estimates of bone compressive and bending strength in a subset (n = 1171) of men (> or =65 years of age) who participated in the multisite Osteoporotic Fractures in Men (MrOS) study. Analysis of covariance-adjusted bone data for clinic site, age, and limb length (model 1) and further adjusted for body weight (model 2) were used to compare data between participants with (n = 190) and without (n = 981) T2DM. At both the distal tibia and radius, patients with T2DM had greater bone vBMD (+2% to +4%, model 1, p < .05) and a smaller bone area (ToA -1% to -4%, model 2, p < .05). The higher vBMD compensated for lower bone area, resulting in no differences in estimated compressive bone strength at the distal trabecular bone regions. At the mostly cortical bone midshaft sites of the radius and tibia, men with T2DM had lower ToA (-1% to -3%, p < .05), resulting in lower bone bending strength at both sites after adjusting for body weight (-2% to -5%, p < .05) despite the lack of difference in cortical vBMD at these sites. These data demonstrate that older men with T2DM have bone strength that is low relative to body weight at the cortical-rich midshaft of the radius despite no difference in cortical vBMD.

Overweight children have a greater proportion of fat mass relative to muscle mass in the upper limbs than in the lower limbs: implications for bone strength at the distal forearm

BACKGROUND

The influence of adiposity on upper-limb bone strength has rarely been studied in children, despite the high incidence of forearm fractures in this population.

OBJECTIVE

The objective was to compare the influence of muscle and fat tissues on bone strength between the upper and lower limbs in prepubertal children.

DESIGN

Bone mineral content, total bone cross-sectional area, cortical bone area (CoA), cortical thickness (CoTh) at the radius and tibia (4% and 66%, respectively), trabecular density (TrD), bone strength index (4% sites), cortical density (CoD), stress-strain index, and muscle and fat areas (66% sites) were measured by using peripheral quantitative computed tomography in 427 children (206 boys) aged 7-10 y.

RESULTS

Overweight children (n = 93) had greater values for bone variables (0.3-1.3 SD; P < 0.0001) than did their normal-weight peers, except for CoD 66% and CoTh 4%. The between-group differences were 21-87% greater at the tibia than at the radius. After adjustment for muscle cross-sectional area, TrD 4%, bone mineral content, CoA, and CoTh 66% at the tibia remained greater in overweight children, whereas at the distal radius total bone cross-sectional area and CoTh were smaller in overweight children (P < 0.05). Overweight children had a greater fat-muscle ratio than did normal-weight children, particularly in the forearm (92 +/- 28% compared with 57 +/- 17%). Fat-muscle ratio correlated negatively with all bone variables, except for TrD and CoD, after adjustment for body weight (r = -0.17 to -0.54; P < 0.0001).

CONCLUSIONS

Overweight children had stronger bones than did their normal-weight peers, largely because of greater muscle size. However, the overweight children had a high proportion of fat relative to muscle in the forearm, which is associated with reduced bone strength.

Common injuries in athletes with obesity and diabetes

Musculoskeletal injuries and diseases are common in persons with obesity and diabetes mellitus. High body mass index is associated with an increased risk for musculoskeletal injuries, diseases, and disability. There is a significant positive correlation between the level of obesity and musculoskeletal injuries, and disability and health-related costs. The prevalence of obesity and diabetes is inversely proportional to health-related quality of life.

Paediatric obesity, physical activity and the musculoskeletal system

The current epidemic of paediatric obesity is consistent with a myriad of health-related comorbid conditions. Despite the higher prevalence of orthopaedic conditions in overweight children, a paucity of published research has considered the influence of these conditions on the ability to undertake physical activity. As physical activity participation is directly related to improvements in physical fitness, skeletal health and metabolic conditions, higher levels of physical activity are encouraged, and exercise is commonly prescribed in the treatment and management of childhood obesity. However, research has not correlated orthopaedic conditions, including the increased joint pain and discomfort that is commonly reported by overweight children, with decreases in physical activity. Research has confirmed that overweight children typically display a slower, more tentative walking pattern with increased forces to the hip, knee and ankle during 'normal' gait. This research, combined with anthropometric data indicating a higher prevalence of musculoskeletal malalignment in overweight children, suggests that such individuals are poorly equipped to undertake certain forms of physical activity. Concomitant increases in obesity and decreases in physical activity level strongly support the need to better understand the musculoskeletal factors associated with the performance of motor tasks by overweight and obese children.

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.

The interrelationships between abdominal adiposity, leptin and bone mineral content in overweight Latino children

BACKGROUND/AIMS

The link between abdominal fat and bone mineral content (BMC), independent of weight, has not been extensively studied. In Latino children, the contributions of abdominal subcutaneous and visceral fat to BMC have not been examined. Research on the effect of leptin on BMC has also been inconclusive.

METHODS

The present study included 256 overweight Latino children (111 girls, 145 boys; mean BMI 28.2; age 11.1 +/- 1.7 years) from Los Angeles, California. Subcutaneous abdominal adipose tissue (SAAT) and intra-abdominal adipose tissue (IAAT) were determined by single-slice magnetic resonance imaging. BMC was measured using dual-energy X-ray absorptiometry.

RESULTS

Independent of age, Tanner stage and weight, abdominal adipose tissue (SAAT + IAAT) was inversely correlated with BMC (r = -0.46, p < 0.0001; n = 256). In girls, there was an inverse correlation between SAAT and BMC (r = -0.38, p < 0.05), between IAAT and BMC (r = -0.32, p < 0.05) and between leptin and BMC (r = -0.39, p < 0.05). In boys, SAAT and BMC were inversely correlated (r = -0.26, p < 0.05), but the correlation between IAAT and BMC was not significant (p = 0.22). Leptin was also inversely correlated with BMC (r = -0.38, p < 0.05) in boys and contributed to the variances in BMC in both girls and boys.

CONCLUSION

Total abdominal adipose fat and leptin are negatively associated with BMC in Latino children. The correlation between SAAT and BMC is stronger in girls than boys. IAAT and BMC are negatively associated in girls but not correlated in boys.

The osteogenic response of undifferentiated human mesenchymal stem cells (hMSCs) to mechanical strain is inversely related to body mass index of the donor

BACKGROUND

While the importance of physical factors in the maintenance and regeneration of bone tissue has been recognized for many years and the mechano-sensitivity of bone cells is well established, there is increasing evidence that body fat constitutes an independent risk factor for complications in bone fracture healing and aseptic loosening of implants. Although mechanical causes have been widely suggested, we hypothesized that the osteogenic mechano-response of human mesenchymal stem cells (hMSCs) may be altered in obese patients.

METHODS

We determined the phenotypic and genotypic response of undifferentiated hMSCs of 10 donors to cyclic tensile strain (CTS) under controlled in vitro conditions and analyzed the potential relationship relevant to the donor's anthropomorphometric and biochemical parameters related to donor's fat and bone metabolism.

RESULTS AND INTERPRETATION

The osteogenic marker genes were all statistically significantly upregulated by CTS, which was accompanied by a significant increase in cell-based ALP activity. Linear correlation analysis revealed that there was a significant correlation between phenotypic CTS response and the body mass index of the donor (r = -0.91, p < 0.001) and phenotypic CTS response was also significantly related to leptin levels (r = -0.68) and estradiol levels (r = 0.67) within the bone marrow microenvironment of the donor. Such an upstream imprinting process mediated by factors tightly related to the donor's fat metabolism, which hampers the mechanosensitivity of hMSCs in obese patients, may be of pathogenetic relevance for the complications associated with obesity that are seen in orthopedic surgery.

How does body fat influence bone mass in childhood? A Mendelian randomization approach

Fat mass may be a causal determinant of bone mass, but the evidence is conflicting, possibly reflecting the influence of confounding factors. The recent identification of common genetic variants related to obesity in children provides an opportunity to implement a Mendelian randomization study of obesity and bone outcomes, which is less subject to confounding and several biases than conventional approaches. Genotyping was retrieved for variants of two loci reliably associated with adiposity (the fat mass and obesity-related gene FTO and that upstream of the MC4R locus) within 7470 children from the Avon Longitudinal Study of Parents and Children (ALSPAC) who had undergone total body DXA scans at a mean of 9.9 yr. Relationships between both fat mass/genotypes and bone measures were assessed in efforts to determine evidence of causality between adiposity and bone mass. In conventional tests of association, both with and without height adjustment, total fat mass was strongly related to total body, spinal, and upper and lower limb BMC (ratio of geometric means [RGM]: 1.118 [95% CI: 1.112, 1.123], 1.110 [95% CI: 1.102, 1.119], 1.101 [95% CI: 1.093, 1.108], 1.146 [95% CI: 1.143, 1.155]; p < 10(-10) [adjusted for sex, height, and sitting height]). Equivalent or larger effects were obtained from instrumental variable (IV) regression including the same covariates (1.139 [95% CI: 1.064, 1.220], 1.090 [95% CI: 1.010, 1.177], 1.142 [95% CI: 1.049, 1.243], 1.176 [95% CI: 1.099, 1.257]; p = 0.0002, 0.03, 0.002, and 2.3(-6) respectively). Similar results were obtained after adjusting for puberty, when truncal fat mass was used in place of total fat, and when bone area was used instead of bone mass. In analyses where total body BMC adjusted for bone area (BA) was the outcome (reflecting volumetric BMD), linear regression with fat mass showed evidence for association (1.004 [95% CI: 1.002, 1.007], p = 0.0001). IV regression also showed a positive effect (1.031 [95% CI: 1.000, 1.062], p = 0.05). When MC4R and FTO markers were used as instruments for fat mass, similar associations with BMC were seen to those with fat mass as measured by DXA. This suggests that fat mass is on the causal pathway for bone mass in children. In addition, both directly assessed and IV-assessed relationships between fat mass and volumetric density showed evidence for positive effects, supporting a hypothesis that fat effects on bone mass are not entirely accounted for by association with overall bone size.

Bone health and back pain: what do we know and where should we go?

Bone health is generally not considered in patients who present with chronic back pain. Nonetheless, bone health and back pain share common genetic and environmental correlates suggesting a co-dependence. Evidence exists for a relationship between back pain and impaired bone health. Here we present the evidence, theoretic framework and clinical relevance. Bone health and back pain are important determinants of musculoskeletal health. Back pain experienced in youth is a risk factor for future back pain, while suboptimal bone health during development increases the risk of skeletal fragility in later life. Generally, bone health is not considered in patients with chronic back pain who do not demonstrate other well-recognised bone health risk factors or associated conditions. Nonetheless, evidence suggests that back pain and impaired bone health share common environmental and genetic correlates, indicating that bone health ought to be considered in the context of back pain in otherwise healthy individuals. This review describes the likely mechanisms explaining the relationship between back pain and impaired bone health, evidence concerning the relationship and suggestions for future research. A narrative literature search was conducted using CINAHL, Medline, PubMed and Web of Science electronic databases. A history of back pain is associated with decreased bone mineral density in adults, yet this tends to be site-specific. No studies were identified examining this association in youth, yet the negative effects of childhood skeletal trauma and obesity on bone and spinal health provide indirect evidence for an association. Further research is required to clarify the impact of back pain on bone health at different lifespan stages using prospective cohort designs.

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.

Relationship between bone mineral density, leptin and insulin concentration in Brazilian obese adolescents

Despite the epidemic of adolescent obesity, the effect of obesity and hormones on bone mineral accrual during growth is poorly understood. Studies using dual-energy X-ray to examine the effect of obesity on bone mass in children and adolescents have yielded conflicting results. The aim of this study was to explore the combined and independent contributions of body mass index, body composition, leptin, insulin, glucose levels and Homeostasis Model Assessment Insulin Resistance (HOMA-IR) to bone mineral density (BMD) and bone mineral content in a group of Brazilian obese adolescents. This study included 109 post-pubescent obese adolescents. A whole-body dual-energy X-ray absorptiometry scan was performed,using a HOLOGIC QDR4200, to determine whole-body BMD and body composition. Blood samples were collected in the outpatient clinic after an overnight fast, and evaluated for fasting blood glucose and immunoreactive insulin. Leptin levels were assessed with a radioimmunoassay kit. Insulin resistance was assessed by HOMA-IR and the quantitative insulin sensitivity check index. Our results showed that insulin levels and HOMA-IR correlated negatively with BMD and a linear regression analysis showed that serum leptin is inversely associated to BMD adjusted for body mass. In conclusion, our data support the hypothesis that leptin, insulin and HOMA-IR are inversely associated with BMD and play a significant direct role in bone metabolism.

Total body, lumbar spine and hip bone mineral density in overweight adolescent girls: decreased or increased?

Despite the epidemic of overweight adolescents, the effect of being overweight on bone mineral density (BMD) during this period is poorly understood. However, recent studies have suggested that overweight adolescents have lower BMD compared to normal-weighted adolescents after adjusting for body weight. The aim of this study was to determine the influence of being overweight on bone status in a group of 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)). Bone mineral area, bone mineral content, BMD at the whole body (WB), lumbar spine (L2-L4), femoral neck (FN), total hip (TH) and body composition (lean mass and fat mass) were assessed by dual-energy X-ray absorptiometry (DXA). Calculation of the bone mineral apparent density (BMAD) was completed for the WB and for L2-L4. Expressed as crude values, DXA measurements of BMD at all bone sites (TB, L2-L4, TH and FN) were higher in overweight adolescent girls compared to controls. After adjusting for either body weight, lean mass or fat mass, these differences disappeared. Finally, BMAD of the L2-L4 remained higher in overweight girls compared to controls after adjusting for lean mass. We conclude that overweight adolescent girls do not have lower BMD when compared with controls, even when BMD values are adjusted for weight, lean mass or fat mass.

Adiposity and TV viewing are related to less bone accrual in young children

OBJECTIVE

To examine the relation between baseline fat mass and gain in bone area and bone mass in preschoolers studied prospectively for 4 years, with a focus on the role of physical activity and TV viewing.

STUDY DESIGN

Children were part of a longitudinal study in which measures of fat, lean and bone mass, height, weight, activity, and diet were taken every 4 months from ages 3 to 7 years. Activity was measured by accelerometer and TV viewing by parent checklist. We included 214 children with total body dual energy x-ray absorptiometry (Hologic 4500A) scans at ages 3.5 and 7 years.

RESULTS

Higher baseline fat mass was associated with smaller increases in bone area and bone mass over the next 3.5 years (P < .001). More TV viewing was related to smaller gains in bone area and bone mass accounting for race, sex, and height. Activity by accelerometer was not associated with bone gains.

CONCLUSIONS

Adiposity and TV viewing are related to less bone accrual in preschoolers.

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.

Dual energy X-ray absorptiometry interpretation and reporting in children and adolescents: the 2007 ISCD Pediatric Official Positions

The International Society for Clinical Densitometry Official Positions on reporting of densitometry results in children represent an effort to consolidate opinions to assist healthcare providers determine which skeletal sites should be assessed, which adjustments should be made in these assessments, appropriate pediatric reference databases, and elements to include in a dual energy X-ray absorptiometry (DXA) report. Skeletal sites recommended for assessment are the lumbar spine and total body less head, the latter being valuable as it provides information on soft tissue, as well as bone. Interpretation of DXA findings in children with growth or maturational delay requires special consideration; adjustments are required to prevent erroneous interpretation. Normative databases used as a reference should be based on a large sample of healthy children that characterizes the variability in bone measures relative to gender, age, and race/ethnicity, and should be specific for each manufacturer and model of densitometer and software. Pediatric DXA reports should provide relevant demographic and health information, technical details of the scan, Z-scores, and should not include T-scores. The rationale and evidence for development of the Official Positions are provided. Given the sparse data currently available in many of these areas, it is likely that these positions will change over time as new data become available.