Solid anthropomorphic infant whole-body DXA phantom: design, evaluation, and multisite testing.

BACKGROUND: Dual-energy X-ray absorptiometry (DXA) requires phantoms for quality control and cross-calibration. No commercially available phantoms are designed specifically for whole-body scanning of infants. METHODS: We fabricated a phantom closely matching a 7-kg human infant in body habitus using polyvinyl chloride (PVC), nylon mix, and polyethylene for bone, lean tissue, and fat, respectively, for evaluating the comparability of instruments used in studies on infant body composition. We scanned the phantom multiple times for short- and long-term repeatability and then shipped it to six other sites for comparison scans. All instruments were Hologic Delphi or Discovery models. Scan analyses were in-house procedures (Hologic V12.1). RESULTS: Short- and long-term results were not significantly different. Nylon mix underrepresented expected lean mass values by 5%, PVC underrepresented bone by 12%, and polyethylene overrepresented fat by 30%. Precision values were as follows: lean mass ≈ 3%; bone ≈ 3.5%; and fat = 5.5-7.5%. Instruments differed significantly for bone mineral content and density results in most instances. Three instruments differed in fat and lean mass. The two Hologic models differed significantly in all compartments except bone density. CONCLUSION: The phantom design came close to emulating bone, lean tissue, and fat and showed good reproducibility. Significant differences among various DXA instruments highlight the necessity of cross-calibration for any multicenter studies.

Effect of soy isoflavone supplementation on menopausal quality of life.

OBJECTIVE: The purpose of this study was to assess the effect of soy isoflavone supplementation on quality of life in postmenopausal women. METHODS: A multicenter, randomized, double-blind, placebo-controlled 24-month trial was conducted to assess the effect of 80 or 120 mg of daily aglycone hypocotyl soy isoflavone supplementation on quality of life in 403 postmenopausal women using a validated Menopause-Specific Quality of Life questionnaire. RESULTS: Menopause-Specific Quality of Life domain scores at 1 year and 2 years were similar to baseline. There were no differences in domain scores among treatment groups. CONCLUSIONS: Soy isoflavone supplementation offers no benefit to quality of life in postmenopausal women.

Assessment of bone mineral status in children with Marfan syndrome.

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder with skeletal involvement. It is caused by mutations in fibrillin1 (FBN1) gene resulting in activation of TGF-ß, which developmentally regulates bone mass and matrix properties. There is no consensus regarding bone mineralization in children with MFS. Using dual-energy X-ray absorptiometry (DXA), we evaluated bone mineralization in 20 children with MFS unselected for bone problems. z-Scores were calculated based on age, gender, height, and ethnicity matched controls. Mean whole body bone mineral content (BMC) z-score was 0.26±1.42 (P=0.41). Mean bone mineral density (BMD) z-score for whole body was -0.34±1.4 (P=0.29) and lumbar spine was reduced at -0.55±1.34 (P=0.017). On further adjusting for stature, which is usually higher in MFS, mean BMC z-score was reduced at -0.677±1.37 (P=0.04), mean BMD z-score for whole body was -0.82±1.55 (P=0.002) and for lumbar spine was -0.83±1.32 (P=0.001). An increased risk of osteoporosis in MFS is controversial. DXA has limitations in large skeletons because it tends to overestimate BMD and BMC. By adjusting results for height, age, gender, and ethnicity, we found that MFS patients have significantly lower BMC and BMD in whole body and lumbar spine. Evaluation of diet, exercise, vitamin D status, and bone turnover markers will help gain insight into pathogenesis of the reduced bone mass. Further, larger longitudinal studies are required to evaluate the natural history, incidence of fractures, and effects of pharmacological therapy.

Decreased bone mineralization in children with Noonan syndrome: another consequence of dysregulated RAS MAPKinase pathway?

INTRODUCTION: Noonan syndrome (NS) is a disorder of RAS- mitogen activated protein kinase (MAPK) pathway with clinical features of skeletal dysplasia. This pathway is essential for regulation of cell differentiation and growth including bone homeostasis. Currently, limited information exists regarding bone mineralization in NS. MATERIALS AND METHODS: Using dual-energy X-ray absorptiometry (DXA), bone mineralization was evaluated in 12 subjects (mean age 8.7 years) with clinical features of NS. All subjects underwent genetic testing which showed mutations in PTPN11 gene (N=8) and SOS1 gene (N=1). In a subgroup of subjects with low bone mass, indices of calcium-phosphate metabolism and bone turnover were obtained. RESULTS: 50% of subjects had low bone mass as measured by DXA. Z-scores for bone mineral content (BMC) were calculated based on age, gender, height, and ethnicity. Mean BMC z-score was marginally decreased at -0.89 {95% CI -2.01 to 0.23; p=0.1}. Mean total body bone mineral density (BMD) z-score was significantly reduced at -1.87 {95% CI -2.73 to -1.0; p=0.001}. Mean height percentile was close to - 2 SD for this cohort, thus total body BMD z-scores were recalculated, adjusting for height age. Adjusted mean total body BMD z-score was less reduced but still significant at -0.82 {95% CI -1.39 to -0.25; p=0.009}. Biochemical evaluation for bone turnover was unremarkable except serum IGF-I and IGF-BP3 levels which were low-normal for age. DISCUSSION: Children with NS have a significantly lower total body BMD compared to age, gender, ethnicity and height matched controls. In addition, total BMC appears to trend lower in children with NS compared to controls. We conclude that the metabolic bone disease present resulted from a subtle variation in the interplay of osteoclast and osteoblast activity, without clear abnormalities being defined in the metabolism of either. Clinical significance of this finding needs to be validated by larger longitudinal studies. Also, histomorphometric analysis of bone tissue from NS patients and mouse model of NS may further elucidate the relationship between the RAS-MAPK pathway and skeletal homeostasis.

Ethnic bias in anthropometric estimates of DXA abdominal fat: the TIGER study.

BACKGROUND/INTRODUCTION: The purpose of this study was to examine the race/ethnicity bias of using waist circumference (WC) to estimate abdominal fat. METHODS: A total of 771 females and 484 males (17-35 yr) were tested one to three times during a prescribed 30-wk aerobic exercise program. The race/ethnicity distribution for women was non-Hispanic white, 29%; Hispanic, 25%; African American (AA), 35%; Asian Indian, 3%; and Asian, 8%. The distribution for men was non-Hispanic white, 37%; Hispanic, 26%; AA, 22%; Asian Indian, 5%; and Asian, 10%. Abdominal fat (L1-L5) was estimated from whole-body scanning using dual-energy x-ray absorptiometry (DXA Abd-Fat). RESULTS: DXA Abd-Fat varied by race/ethnicity after accounting for WC and height in both women and men. The increase in DXA Abd-Fat per increase in WC was lower in the Asian and Asian-Indian women than that in the other women. The increase in DXA Abd-Fat per increase in WC was higher in the AA men and lower in the Asian-Indian men than that in the other men. These differential race/ethnicity effects were most notable when WC exceeded ≍90 cm in the women and ≍100 cm in the men, values which are consistent with current definitions of abdominal obesity in the United States. CONCLUSIONS: Prediction equations for abdominal fat using WC that do not account for race/ethnicity group provide biased estimates. These results may affect assessment of disease risk from abdominal obesity among racial/ethnic groups.

Clinical outcomes of a 2-y soy isoflavone supplementation in menopausal women.

BACKGROUND: Soy isoflavones are naturally occurring phytochemicals with weak estrogenic cellular effects. Despite numerous clinical trials of short-term isoflavone supplementation, there is a paucity of data regarding longer-term outcomes and safety. OBJECTIVE: Our aim was to evaluate the clinical outcomes of soy hypocotyl isoflavone supplementation in healthy menopausal women as a secondary outcome of a trial on bone health. DESIGN: A multicenter, randomized, double-blind, placebo-controlled 24-mo trial was conducted to assess the effects of daily supplementation with 80 or 120 mg aglycone equivalent soy hypocotyl isoflavones plus calcium and vitamin D on the health of 403 postmenopausal women. At baseline and after 1 and 2 y, clinical blood chemistry values were measured and a well-woman examination was conducted, which included a mammogram and a Papanicolaou test. A cohort also underwent transvaginal ultrasound measurements to assess endometrial thickness and fibroids. RESULTS: The baseline characteristics of the groups were similar. After 2 y of daily isoflavone exposure, all clinical chemistry values remained within the normal range. The only variable that changed significantly was blood urea nitrogen, which increased significantly after 2 y (P = 0.048) but not after 1 y (P = 0.343) in the supplementation groups. Isoflavone supplementation did not affect blood lymphocyte or serum free thyroxine concentrations. No significant differences in endometrial thickness or fibroids were observed between the groups. Two serious adverse events were detected (one case of breast cancer and one case of estrogen receptor-negative endometrial cancer), which was less than the expected population rate for these cancers. CONCLUSION: Daily supplementation for 2 y with 80-120 mg soy hypocotyl isoflavones has minimal risk in healthy menopausal women. This trial was registered at clinicaltrials.gov as NCT00665860.

Chronic parenteral nutrition induces hepatic inflammation, steatosis, and insulin resistance in neonatal pigs.

Prematurity and overfeeding in infants are associated with insulin resistance in childhood and may increase the risk of adult disease. Total parenteral nutrition (TPN) is a major source of infant nutritional support and may influence neonatal metabolic function. Our aim was to test the hypothesis that TPN induces increased adiposity and insulin resistance compared with enteral nutrition (EN) in neonatal pigs. Neonatal pigs were either fed enteral formula orally or i.v. administered a TPN mixture for 17 d; macronutrient intake was similar in both groups. During the 17-d period, we measured body composition by dual-energy X-ray absorptiometry scanning; fasting i.v. glucose tolerance tests (IVGTT) and hyperinsulinemic-euglycemic clamps (CLAMP) were performed to quantify insulin resistance. On d 17, tissue was collected after 1-h, low-dose CLAMP for tissue insulin signaling assays. TPN pigs gained less lean and more body fat and developed hepatic steatosis compared with EN pigs. After 7 and 13 d, IVGTT showed evidence of insulin resistance in the TPN compared with the EN group. Fasting plasma glucose and insulin also were higher in TPN pigs. CLAMP showed that insulin sensitivity was markedly lower in TPN pigs than in EN pigs. TPN also reduced the abundance of the insulin receptor, insulin receptor substrate 1, and phosphatidylinositol 3 kinase in skeletal muscle and liver and the proliferation of total pancreatic cells and ß-cells. Hepatic proinflammatory genes as well as c-Jun-N-terminal kinase 1 phosphorylation, plasma interleukin 6, and tumor necrosis factor-α were all higher in TPN pigs than in EN pigs. The results demonstrate that chronic TPN induces a hepatic inflammatory response that is associated with significant insulin resistance, hepatic steatosis, and fat deposition compared with EN in neonatal pigs. Further studies are warranted to establish the mechanism of TPN-induced insulin resistance and hepatic metabolic dysfunction and whether there are persistent metabolic consequences of this lifesaving form of infant nutritional support.

Exposing college students to exercise: the Training Interventions and Genetics of Exercise Response (TIGER) study.

OBJECTIVE: The Training Interventions and Genetics of Exercise Response (TIGER) study is an exercise program designed to introduce sedentary college students to regular physical activity and to identify genetic factors that influence response to exercise. PARTICIPANTS: A multiracial/ethnic cohort (N = 1,567; 39% male), age 18 to 35 years, participated in the study. METHODS: Subjects underwent 30 weeks of exercise training, 3 days/week, for 40 minutes at 65% to 85% of age- and gender-predicted maximum heart rate reserve. Multiple measures of body size/composition, heart rate, and blood pressure were obtained. RESULTS: A total of 1,567 participants, (39% male), age 18 to 35 years, participated in the TIGER study. The prevalence of overweight/obesity in participants was 48.0%/19.3% in non-Hispanic Whites, 55.3%/24.2% in Hispanic Whites, 54.9%/25.4% in African Americans, and 38.3%/11.3% in Asians. Average within-semester retention was 68%, but overall retention (30 weeks, 2 semesters) was 20%. CONCLUSIONS: The TIGER study represents an efficacious strategy for introducing college-aged individuals to regular aerobic exercise.

Generalized equations for estimating DXA percent fat of diverse young women and men: the TIGER study.

PURPOSE: Popular generalized equations for estimating percent body fat (BF%) developed with cross-sectional data are biased when applied to racially/ethnically diverse populations. We developed accurate anthropometric models to estimate dual-energy x-ray absorptiometry BF% (DXA-BF%) that can be generalized to ethnically diverse young adults in both cross-sectional and longitudinal field settings. METHODS: This longitudinal study enrolled 705 women and 428 men (aged 17-35 yr) for 30 wk of exercise training (3 d·wk(-1) for 30 min·d(-1) of 65%-85% predicted V˙O2max). The distribution of ethnicity was as follows: 37% non-Hispanic white, 29% Hispanic, and 34% African-American. DXA-BF%, skinfold thicknesses, and body mass index (BMI) were collected at baseline and after 15 and 30 wk. RESULTS: Skinfolds, BMI, and race/ethnicity were significant predictors of DXA-BF% in linear mixed model regression analysis. For comparable anthropometric measures (e.g., BMI), DXA-BF% was lower in African-American women and men but higher in Hispanic women compared with non-Hispanic white. Addition of BMI to the skinfold model improved the SEE for women (3.6% vs 4.0%), whereas BMI did not improve prediction accuracy of men (SEE = 3.1%). CONCLUSIONS: These equations provide accurate predictions of DXA-BF% for diverse young women and men in both cross-sectional and longitudinal settings. To our knowledge, these are the first published body composition equations with generalizability to multiple time points, and the SEE estimates are among the lowest published in the literature.

Body composition in infancy: impact on health later in life.

From retrospective studies, there is substantial evidence that birthweight and the rate of weight gain during early infancy are associated with increased risk for adverse health outcomes later in life. Birthweight is the marker of the integrative effects of the prenatal environment, while the rate of weight gain after birth reflects both genetic potential and external postnatal influences. The adulthood-to-infancy associations constitute the basis for the 'fetal origins' and 'catch-up growth' hypotheses for some diseases. However, these findings are based on the assumption that anthropometric-based indices reflect body composition during both time periods, with the body mass index (weight/stature2) being the most frequently used index. More direct measures of body composition were simply not available at the time of the births of the adults participating in these studies. Nowadays, there are a number of in vivo techniques that can be used to examine body composition in infancy. In particular, what does the body mass index reflect in terms of body composition for the infant? Is it an adequate index?

Soy isoflavone supplementation and bone mineral density in menopausal women: a 2-y multicenter clinical trial.

BACKGROUND: Isoflavones are naturally occurring plant estrogens that are abundant in soy. Although purported to protect against bone loss, the efficacy of soy isoflavone supplementation in the prevention of osteoporosis in postmenopausal women remains controversial. OBJECTIVE: Our aim was to test the effect of soy isoflavone supplementation on bone health. DESIGN: A multicenter, randomized, double-blind, placebo-controlled 24-mo trial was conducted to assess the effects of daily supplementation with 80 or 120 mg of soy hypocotyl aglycone isoflavones plus calcium and vitamin D on bone changes in 403 postmenopausal women. Study subjects were tested annually and changes in whole-body and regional bone mineral density (BMD), bone mineral content (BMC), and T scores were assessed. Changes in serum biochemical markers of bone metabolism were also assessed. RESULTS: After study site, soy intake, and pretreatment values were controlled for, subjects receiving a daily supplement with 120 mg soy isoflavones had a statistically significant smaller reduction in whole-body BMD than did the placebo group both at 1 y (P < 0.03) and at 2 y (P < 0.05) of treatment. Smaller decreases in whole-body BMD T score were observed among this group of women at 1 y (P < 0.03) but not at 2 y of treatment. When compared with the placebo, soy isoflavone supplementation had no effect on changes in regional BMD, BMC, T scores, or biochemical markers of bone metabolism. CONCLUSION: Daily supplementation with 120 mg soy hypocotyl isoflavones reduces whole-body bone loss but does not slow bone loss at common fracture sites in healthy postmenopausal women. This trial was registered at clinicaltrials.gov as NCT00665860.

Body mass index bias in defining obesity of diverse young adults: the Training Intervention and Genetics of Exercise Response (TIGER) study.

The BMI cut-score used to define overweight and obesity was derived primarily using data from Caucasian men and women. The present study evaluated the racial/ethnic bias of BMI to estimate the adiposity of young men and women (aged 17-35 years) using dual-energy X-ray absorptiometry (DXA) determination of percentage body fat (DXA-BF%) as the referent standard. The samples were 806 women and 509 men who were tested from one to three times over 9 months providing 1300 observations for women and 820 observations for men. Linear mixed models (LMM) regression showed that with age and BMI controlled, DXA-BF% of African-American (AA) men and women, Asian-Indian men and women, Hispanic women and Asian women significantly differed from non-Hispanic white (NHW) men and women. For the same BMI of NHW women, the DXA-BF% of AA women was 1.76 % lower, but higher for Hispanic (1.65 %), Asian (2.65 %) and Asian-Indian (5.98 %) women. For the same BMI of NHW men, DXA-BF% of AA men was 4.59 % lower and 4.29 % higher for Asian-Indian men. Using the recommended BMI cut-scores to define overweight and obesity systematically overestimated overweight and obesity prevalence for AA men and women, and underestimated prevalence for Asian-Indian men and women, Asian women and Hispanic women. The present study extends the generalisability of research documenting the racial/ethnic bias of the universal overweight and obesity BMI cut-scores.

Impact of body composition on pharmacokinetics of doxorubicin in children: a Glaser Pediatric Research Network study.

PURPOSE: We studied the relationship between doxorubicin pharmacokinetics and body composition in children with cancer. PATIENTS AND METHODS: Children between 1 and 21 years of age, receiving doxorubicin as an infusion of any duration <24 h on either a 1-day or 2-day schedule were eligible if they had no significant abnormality of liver function tests, their dose of doxorubicin was not based on ideal body weight or otherwise "capped," and they weighed > or =12 kg. Body composition was measured by dual-energy X-ray absorptiometry. Doxorubicin and doxorubicinol concentration in plasma were measured by high pressure liquid chromatography. NONMEM was used to perform pharmacokinetic model fitting and S-PLUS was used to perform a post hoc analysis to examine the effect of body composition on pharmacokinetic parameters. RESULTS: Twenty-two subjects (16 male; 10 Hispanic, 10 Caucasian, 2 Asian) completed the study. The median age was 15.0 years (range 3.3-21.5), median weight was 51.5 kg (range 12.4-80), median BMI was 19.7 (range 13.2-30.0), and median body fat was 25% (range 15-36). The population mean clearance of doxorubicin was 420 ml/min/m(2). Doxorubicinol but not doxorubicin clearance was lower in patients with body fat greater than 30%. CONCLUSIONS: Doxorubicinol clearance is decreased in children with >30% body fat. This finding is potentially important clinically, because doxorubicinol may contribute significantly to cardiac toxicity after doxorubicin administration. Further study of the body composition on doxorubicin and doxorubicinol pharmacokinetics and on clinical outcomes is warranted.

Cross-validation of generalised body composition equations with diverse young men and women: the Training Intervention and Genetics of Exercise Response (TIGER) Study.

Generalised skinfold equations developed in the 1970s are commonly used to estimate laboratory-measured percentage fat (BF%). The equations were developed on predominately white individuals using Siri's two-component percentage fat equation (BF%-GEN). We cross-validated the Jackson-Pollock (JP) generalised equations with samples of young white, Hispanic and African-American men and women using dual-energy X-ray absorptiometry (DXA) as the BF% referent criterion (BF%-DXA). The cross-sectional sample included 1129 women and men (aged 17-35 years). The correlations between BF%-GEN and BF%-DXA were 0.85 for women and 0.93 for men. Analysis of measurement error showed that BF%-GEN underestimated BF%-DXA of men and women by 1.3 and 3.0 %. General linear models (GLM) confirmed that BF%-GEN systematically underestimated BF%-DXA of Hispanic men and women, and overestimated BF%-DXA of African-American men. GLM were used to estimate BF%-DXA from the JP sum of skinfolds and to account for race/ethnic group bias. The fit statistics (R and standard error of the estimate; see) of the men's calibration model were: white, R 0.92, see 3.0 %; Hispanic, R 0.91, see 3.0 %; African-American, R 0.95, see 2.6 %. The women's statistics were: white and African-American, R 0.86, see 3.8 %; Hispanic, R 0.83, see 3.4 %. These results showed that BF%-GEN and BF%-DXA were highly correlated, but the error analyses documented that the generalised equations lacked accuracy when applied to these racially and ethnically diverse men and women. The inaccuracy was linked to the body composition and race/ethnic differences between these Training Intervention and Genetics of Exercise Response (TIGER) study subjects and the men and women used to develop the generalised equations in the 1970s and using BF%-DXA as the referent criterion.

Bone mineral content and bone mineral density are lower in older than in younger females with Rett syndrome.

Although bone mineral deficits have been identified in Rett syndrome (RTT), the prevalence of low bone mineral density (BMD) and its association with skeletal fractures and scoliosis has not been characterized fully in girls and women with RTT. Accordingly, we measured total body bone mineral content (BMC) and BMD using dual energy x-ray absorptiometry in a cross-sectional group of 50 females, aged 2-38 y, with RTT. Methyl-CpG-binding 2 (MECP2) mutations, skeletal fractures, and scoliosis were documented. The prevalence of BMC and BMD z scores < or-2 SD was 59 and 45%, respectively. Although absolute BMC and BMD increased significantly with increasing age, BMC, and BMD z scores were significantly lower in older than in younger females. The prevalence of fractures and scoliosis was 28 and 64%, respectively. Low BMD z scores were positively associated with fractures and scoliosis. Deficits in BMD were identified across a broad range of MECP2 mutations. This study identified associations among low BMD, fractures, and scoliosis, and underscored the need for better understanding of the molecular mechanisms of MECP2 in the regulation of bone mineral metabolism.

DXA: can it be used as a criterion reference for body fat measurements in children?

OBJECTIVE: Dual-energy X-ray absorptiometry (DXA) is often cited as a criterion method for body composition measurements. We have previously shown that a new DXA software version (Hologic Discovery V12.1) will affect whole-body bone mineral results for subjects weighing <40 kg. We wished to reanalyze pediatric whole-body scans in order to assess the impact of the new software on pediatric soft-tissue body composition estimates. METHODS AND PROCEDURES: We reanalyzed 1,384 pediatric scans (for ages 1.7-17.2 years) using Hologic software V12.1, previously analyzed using V11.2. Regression analysis and ANCOVA were used to compare body fat (total body fat (TBF), percentage fat (%BF)), and non-bone lean body mass (LBM) for the two versions, adjusting for gender, age and weight. RESULTS: Software V12.1 yielded values that were higher for TBF, lower for LBM, and unchanged for DXA-derived weight in subjects weighing <40 kg. Body composition values for younger, smaller subjects were most affected, and girls were more affected than boys. Using the new software, 14% of the girls and 10% of the boys were reclassified from the "normal" %BF range to "at risk of obesity," while 7 and 5%, respectively, were reclassified as obese. DISCUSSION: Hologic's newest DXA software has a significant effect on soft-tissue results for children weighing <40 kg. The effect is greater for girls than boys. Comparison of TBF estimates with previous studies that use older DXA instruments and software should be done with caution. DXA has not yet achieved sufficient reliability to be considered a "gold standard" for body composition assessment in pediatric studies.

Generalized metabolic bone disease in Neurofibromatosis type I.

Skeletal abnormalities are a recognized component of Neurofibromatosis type I (NF1) but a generalized metabolic bone defect in NF1 has not been fully characterized thus far. The purpose of this study was to characterize at the densitometric, biochemical and pathological level the bone involvement in NF1 patients. Using dual energy X-ray absorptiometry (DXA) we analyzed bone status in 73 unselected NF1 subjects, 26 males and 47 females, mainly children and adolescents (mean age: 16.6 years). In a subgroup of subjects with low bone mass, we measured indices of calcium-phosphate metabolism, bone turnover, and bone density before and after vitamin D and calcium treatment. We found statistically significant and generalized reduction in bone mass with the mean lumbar bone mineral density (BMD) z-score being -1.38+/-1.05 (CI 95% -1.62 to -1.13), and whole body bone mineral content (BMC) z-score -0.61+/-1.19 (CI 95% -0.94 to -0.29), both significantly reduced compared to normal controls (p<.001). PTH was moderately elevated and after 4 months of supplemental therapy with calcium and vitamin D, it decreased to the normal range. However, BMD z-scores did not significantly improve after 2 years of follow-up. Histological analysis of bone samples from NF1 patients revealed substantial alteration of bone microarchitecture due mainly to reduced trabecular bone. Our observations are consistent with a generalized bone metabolic defect due to loss of the function of neurofibromin. Early identification of patients with osteoporosis may permit more timely and aggressive treatments to prevent the likely substantial morbidity associated with increased fracture risk later in life.

Effect of prebiotic supplementation and calcium intake on body mass index.

OBJECTIVE: To assess the effects of a prebiotic supplement and usual calcium intake on body composition changes during pubertal growth. STUDY DESIGN: We measured anthropometry and body fat with dual-energy X-ray absorptiometry in 97 young adolescents who were randomized to receive either a daily prebiotic supplement or maltodextrin (control) for 1 year. RESULTS: Subjects who received the prebiotic supplement had a smaller increase in body mass index (BMI) compared with the control group (BMI difference 0.52 +/- 0.16 kg/m2, P = .016), BMI Z-score (difference 0.13 +/- 0.06, P = .048) and total fat mass (difference 0.84 +/- 0.36 kg, P = .022). The prebiotic group maintained their baseline BMI Z-score (0.03 +/- 0.01, paired t test, P = .30), although BMI Z-score increased significantly in the control group (0.13 +/- 0.03, P < .001). In considering subjects whose usual calcium intake was > or = 700 mg/d, those who received the prebiotic supplement had a relative change in BMI that was 0.82 kg/m2 less than control subjects (P < .01), and BMI Z-score that was 0.20 less than control subjects (P = .003). Differences tended to be maintained 1 year after supplementation was stopped. CONCLUSION: Prebiotic supplementation and avoidance of a low calcium intake can have significant effects in modulating BMI and other body composition changes during puberty.

Metabolic and behavioral predictors of weight gain in Hispanic children: the Viva la Familia Study.

BACKGROUND: Despite the high prevalence of overweight among Hispanic children in the United States, definitive predictors of weight gain have not been identified in this population. OBJECTIVE: The study objective was to test sociodemographic, metabolic, and behavioral predictors of 1-y weight gains in a large cohort of Hispanic children studied longitudinally. DESIGN: Subjects (n = 879) were siblings from 319 Hispanic families enrolled in the Viva la Familia Study. Families were required to have at least one overweight child aged 4-19 y. One-year changes in weight and body composition by dual-energy X-ray absorptiometry were measured. Data were from parental interviews, birth certificates, multiple-pass 24-h dietary recalls, 3-d accelerometry, 24-h respiration calorimetry, measurements of eating in the absence of hunger, and measurement of fasting blood biochemistry indexes by radioimmunoassay. Generalized estimating equations and principal component analysis were applied. RESULTS: Weight gain increased with age (P = 0.001), peaking at approximately 10 y of age in girls and approximately 11 y of age in boys. Mean (+/-SD) weight gain was significantly higher in overweight (7.5 +/- 3.7 kg/y) than in nonoverweight (4.4 +/- 2.4 kg/y) children and in boys than in girls. When adjusted for age, age squared, sex, and Tanner stage, the final model indicated a child's body mass index (BMI; kg/m2) status, maternal BMI, energy expenditure (total energy expenditure, basal metabolic rate, and sleeping metabolic rate), and fasting blood biochemistry indexes (total triiodothyronine, insulin, leptin, and ghrelin) as independent, positive predictors of weight gain (P = 0.01-0.001). CONCLUSION: Knowledge of the metabolic and behavioral predictors of weight gain in Hispanic children will inform prevention and treatment efforts to address this serious public health problem in the United States.

Visceral and subcutaneous adiposity measurements in adults: influence of measurement site.

OBJECTIVE: Excess abdominal adiposity is a known risk factor for cardiovascular diseases. Computed tomography can be used to examine the visceral (VAT) and subcutaneous (SAT) components of abdominal adiposity, but it is unresolved whether single-slice or multi-slice protocols are needed. RESEARCH METHOD AND PROCEDURES: Nine computed tomography scans were obtained in the lumbar spine region of 24 adults. The nine slices were obtained at three intervertebral positions (L2-L3, L3-L4, and L4-L5) and at 7 mm above and below these locations. Intra-site and inter-site differences in SAT, VAT, total adipose tissue, and the VAT/SAT ratio were examined using ANOVA and confidence intervals for pairwise differences between means. RESULTS: Intervertebral SAT values increased from 103.1 +/- 50.9 (standard deviation) cm(2) at L2-L3 to 153.3 +/- 68.8 cm(2) at L4-L5, whereas the corresponding VAT values decreased from 164.3 +/- 125.4 to 126.0 +/- 82.7 cm(2). The VAT/SAT ratio was not constant, decreasing from 1.8 +/- 1.4 to 0.9 +/- 0.7. Repeated-measures ANOVA indicated significant inter- and intra-site differences (p