Prediction models for bone mineral content in school-aged children.
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Adolescent↗
Biomedical subjects
K J Ellis
Publications and source records attributed to K J Ellis.
Human body composition: in vivo methods.
In vivo methods used to study human body composition continue to be developed, along with more advanced reference models that utilize the information obtained with these technologies. Some methods are well established, with a strong physiological basis for their measurement, whereas others are much more indirect. This review has been structured from the methodological point of view to help the reader understand what can be examined with each technique. The associations between the various in vivo methods (densitometry, dilution, bioelectrical impedance and conductance, whole body counting, neutron activation, X-ray absorptiometry, computer tomography, and magnetic resonance imaging) and the five-level multicompartment model of body composition are described, along with the limitations and advantages of each method. This review also provides an overview of the present status of this field of research in human biology, including examples of reference body composition data for infants, children, adolescents, and adults.
Adolescent↗
Body composition during the first 2 years of life: an updated reference.
Normative body composition during the first 2 y of life was derived from a prospective study of 76 children. We present 1) fat free mass (FFM) and its components, and fat mass (FM), 2) incremental growth rates partitioned into chemical components, and 3) age-specific and gender-specific constants for converting chemical and physical components into FFM for children during the first 2 y of life. A multicomponent model based on measurements of total body water (TBW), total body potassium (TBK) and bone mineral content (BMC) was used to estimate FFM and FM at 0.5, 3, 6, 9, 12, 18, and 24 mo of age. TBW was determined by deuterium dilution, TBK by whole body counting, and BMC by dual energy x-ray absorptiometry. FFM was higher in boys than girls between 0.5-18 mo of age (p < or = 0.05). Percent FM increased on average from 13 to 31% between 0.5 and 3-6 mo, and then gradually declined. Percent FM was significantly higher in girls than in boys at 6 and 9 mo of age (p < or = 0.02). The components of FFM on a percentage basis changed with age (p = 0.001), but not gender. The protein content of FFM increased gradually with age, while TBW declined (p = 0.001). As a percentage of FFM, osseous mineral increased from 2.0 to 3.4% in boys and from 2.1 to 3.3% in girls between 0.5 and 24 mo (p = 0.001). Density and potassium content of FFM increased gradually with age (p = 0.001). These normative body composition data provide an updated reference upon which to assess normal growth and nutritional status of pediatric populations representative of mixed feeding groups during the first 2 y of life.
Absorptiometry, Photon↗
Calcium absorption, bone mass accumulation, and kinetics increase during early pubertal development in girls.
To evaluate the changes in calcium and bone mineral metabolism associated with early pubertal development, we performed longitudinal measurements of calcium absorption, calcium kinetics, bone mineral content, and hormonal markers related to puberty in a multiethnic group of girls beginning when they were 7 or 8 yr old. Girls were Tanner stage 1 (breast) at the start of the study. They were placed on a 1200 mg/day dietary calcium intake and studied at approximately 6-month intervals until they reached Tanner stage 2 (breast). Results at that time point (PUB) were compared to values obtained approximately 1 yr earlier (LatePRE) and those 1 yr before that (EarlyPRE). We found an increase in calcium absorption comparing PUB to LatePRE (n = 34; 36.6 +/- 8.7% vs. 30.7 +/- 9.9%; P = 0.002). Using whole body, dual energy, x-ray absorptiometry scanning, we found an increase in calcium gain during the LatePRE to PUB period compared with that during the EarlyPRE to LatePRE period (135 +/- 53 vs. 110 +/- 45 mg/day; P = 0.04). Calcium kinetic studies showed a significant increase in the bone calcium deposition rate (Vo+) during the PUB compared to the LatePRE period. Hormonal and biochemical markers of bone development were also significantly increased at PUB compared to LatePRE. Hormonal activity, as evidenced by the unstimulated LH level, was significantly correlated with calcium gain between the LatePRE and PUB studies and the bone calcium deposition rate in the PUB study. These data demonstrate, using multiple independent methods, an increase in calcium utilization associated with the earliest physical signs of puberty.
Black People↗
Ethnic differences in androgens, IGF-I and body fat in healthy prepubertal girls.
OBJECTIVE: To examine ethnic differences in adrenal androgen production, IGF-I, and IGFBP-1 and -3 in relation to bone age, insulin, and body composition in healthy prepubertal girls. METHODS: Serum levels of DHEA-S, androstenedione, IGF-I, and IGFBP-1 and -3 were examined in relation to bone age, insulin, and body composition (determined by dual-energy X-ray absorptiometry) in 47 (19 Caucasian, 9 African-American, 19 Mexican-American) healthy prepubertal girls aged 7.5-9.0 years. RESULTS: Age, weight, height, bone age, androstenedione, insulin, glucose:insulin ratios, and IGFBP-3 levels were not statistically different among groups. Mexican-American girls had higher % body fat than African-Americans or Caucasians (P < 0.001). DHEA-S levels in African-Americans were twofold higher than in Caucasians (P = 0.024), although their % body fat was not significantly different (16.1% and 19.4%, respectively; P = 0.138). DHEA-S levels in Mexican-American girls were intermediate. Bone age and weight were significant covariates for DHEA-S levels. Plasma IGF-I levels were also higher in African-American than in Caucasian or Mexican-American girls (P = 0.009). Covariance analysis showed that IGF-I levels were influenced mainly by ethnicity (P = 0.009) and were independent of bone age. Despite similar insulin levels among groups, IGFBP-1 levels were higher in Caucasians than in Mexican-Americans or African-Americans (P < 0.001). CONCLUSIONS: In healthy prepubertal girls, DHEA-S concentrations are higher in African-Americans than in Caucasians or Mexican-Americans, even before any clinical evidence of adrenarche. Furthermore, IGF-I concentrations are higher in African-American girls than in Caucasian or Mexican-American girls which may contribute to the higher DHEA-S levels observed. Conversely, higher DHEA-S and IGF-I levels in African-American girls may be indicative of an influence not only of gonadal but also of adrenal androgens on the GH/IGF-I axis.
Adipose Tissue↗
Infant feeding mode affects early growth and body composition.
BACKGROUND: Differences in the growth pattern of breastfed (BF) and formula-fed (FF) infants are well-recognized and have been attributed to differences in nutrient intake. However, the impact of qualitative and quantitative differences in nutrient intake on the body composition of BF and FF infants has been unclear. Furthermore, it is unknown whether putative differences in body composition persist beyond weaning. DESIGN: Prospective cohort study. METHODS: Repeated anthropometric and body composition measurements were performed on 40 BF and 36 FF infants at 0.5, 3, 6, 9, 12, 18, and 24 months of age. A multicomponent body composition model based on total body water by deuterium dilution, total body potassium by whole body counting, and bone mineral content by dual-energy x-ray absorptiometry was used to estimate fat-free mass (FFM) and fat mass (FM). Independent measurements of FFM and FM were made using total body electrical conductivity and dual-energy x-ray absorptiometry. By design, infants were either exclusively BF or FF from birth to 4 months of age; thereafter, the feeding mode was at the discretion of the parents. Infant food intake was measured at 3, 6, 12, and 24 months of age using 3-day weighed-intake records. Data were analyzed by repeated measures analysis of variance. RESULTS: Weight velocity was higher in FF than BF infants age 3 to 6 months, and higher in FF than BF girls 6 to 9 months of age. Adjusted for gender and baseline values, BF infants had lower total body water at 3 months, lower total body potassium at 3 to 24 months, and lower bone mineral content at 12 months. The multicomponent model indicated that FFM was lower in BF than FF infants at 3 months, and FM and %FM were higher in BF than FF infants at 3 and 6 months (boys only). Total body electric conductivity confirmed lower FFM in BF than FF infants at 3 months, as well as at 6 and 9 months; FM and %FM were higher in BF than FF at 3 and 6 months, and 9 months (boys only). Intakes of energy, protein, fat, and carbohydrate were lower in BF than FF infants at 3 and 6 months, and were positively correlated with weight gain and FFM gain, but not FM gain. No differences in nutrient intakes were observed at 12 or 24 months. CONCLUSION: Infant feeding mode is associated with differences in body composition in early infancy which do not persist into the second year of life.
Absorptiometry, Photon↗
Effects of rheumatic disease and corticosteroid treatment on calcium metabolism and bone density in children assessed one year after diagnosis, using stable isotopes and dual energy x-ray absorptiometry.
OBJECTIVE: To evaluate calcium (Ca) metabolism and bone mineral density (BMD) in children with rheumatic disease (RD) at diagnosis and one year later, and effects of different therapies. METHODS: We used dual tracer isotope studies and dual energy x-ray absorptiometry (DEXA) to measure Ca metabolism and BMD in 13 children with RD at diagnosis and one year later. Seven subjects were treated with steroids (RD-ST), 6 with antiinflammatory agents (RD-NS), excluding steroids. RESULTS: Ca balance data for RD subjects were not significantly different from data reported previously for healthy sex and age matched controls. True Ca absorption (Va) was slightly but not significantly greater at study entry in RD-NS subjects (313+/-67 vs 239+/-112 mg/day in RD-ST subjects; p = 0.13). Calculated Ca balance retention (Vbal) was higher at entry in RD-NS (200+/-51 vs RD-ST 60+/-125 mg/day; p = 0.08). One year later, Vbal remained higher in RD-NS (202+/-77 mg/day vs RD-ST 101+/-157 mg/day; p = 0.02). BMD was similar in both groups at entry (RD-NS 0.81+/-0.06 g/cm2 vs RD-ST 0.89+/-0.1 g/cm2; p = 0.07). One year later, BMD was 0.86+/-0.6 g/cm2 in RD-NS versus 0.89+/-0.08 g/cm2 in RD-ST; p = 0.07. Ca kinetic and DEXA studies did not reveal significant alteration of Ca kinetics or significantly lower BMD in steroid treated subjects versus non-steroid treated subjects. However, slightly lower Va and Vbal indicated a possible risk of bone demineralization in steroid treated subjects. CONCLUSION: Children with RD who are treated with steroids may be at greater risk of bone demineralization at diagnosis that persists through the first year. However, bone loss may take years to manifest when measured by quantitative methods such as DEXA.
Absorptiometry, Photon↗
Monitoring childhood obesity: assessment of the weight/height index.
The body mass index (BMI), defined as weight/height, is often used to monitor childhood obesity. BMI values for 979 children (438 White, 283 Black, and 258 Hispanic) aged 3-18 years living in the Houston, Texas, metropolitan area from 1994 to 1998 were compared with percentage of fat (%Fat) measurements obtained by using dual-energy x-ray absorptiometry. The associations between %Fat and BMI were statistically significant (r2 = 0.34-0.70, p < 0.0005) and were gender and ethnic dependent (p < 0.0005), indicating that BMI can provide a general description of the adiposity characteristics of a healthy pediatric population. However, BMI was a poor predictor for the individual child, with a standard error for %Fat of 4.7-7.3% of body weight. It is advantageous to identify accurately, as early as possible, those children who truly have excess adiposity, but this assessment should not be done at the risk of falsely mislabeling a significant number of healthy children as overweight or obese.
Absorptiometry, Photon↗
Serum concentrations of insulin, insulin-like growth factor-I and insulin-like growth factor binding proteins are different between white and African American girls.
OBJECTIVES: To determine whether serum insulin-like growth factor (IGF)-I and IGF binding protein (IGFBP) concentrations are different between African American and white girls. STUDY DESIGN: Serum glucose and hormone concentrations were measured in blood samples collected after a 12-hour fast from 79 white and 57 African American healthy girls between 9 and 17 years of age. Tanner stages of pubic hair development were evaluated by physical examination, and body composition by dual energy x-ray absorptiometry. RESULTS: The African American girls were older and sexually more mature and had higher fat mass, higher serum insulin and free IGF-I concentrations, higher serum free IGF-I to total IGF-I ratio, but lower serum IGFBP-1 concentrations than the white girls. After controlling for sexual maturation and fat mass, the serum concentrations of total IGF-I, bound IGF-I, and IGFBP-3 in the white girls became significantly higher than those in the African American girls. The higher concentrations of total IGF-I in the white girls were due to a proportional increase in the concentrations of bound IGF-I that coincided with a similar increase in serum IGFBP-3 concentrations. CONCLUSIONS: Higher serum insulin concentrations in the African American girls are associated with lower serum IGFBP-1 concentrations and increased bioavailability of free IGF-I, which may contribute to their accelerated growth compared with their white counterparts.
Absorptiometry, Photon↗
Total body-calcium measurements: comparison of two delayed-gamma neutron activation facilities.
This study compares two independently calibrated delayed-gamma neutron activation (DGNA) facilities, one at the Brookhaven National Laboratory (BNL), Upton, New York, and the other at the Children's Nutrition Research Center (CNRC), Houston, Texas that measure total body calcium (TBCa). A set of BNL phantoms was sent to CNRC for neutron activation analysis, and a set of CNRC phantoms was measured at BNL. Both facilities showed high precision (< 2%), and the results were in good agreement, within 5%.
Calcium↗
Measurement of body water by multifrequency bioelectrical impedance spectroscopy in a multiethnic pediatric population.
BACKGROUND: Bioelectrical impedance spectroscopy (BIS) may provide a noninvasive, rapid method for the assessment of total body water (TBW), extracellular water (ECW), and intracellular water (ICW). Few studies, however, have examined the accuracy of BIS in pediatric populations. OBJECTIVE: Our objective was to evaluate the accuracy of BIS for the measurement of TBW, ECW, and ICW in healthy children. DESIGN: Dual-energy X-ray absorptiometry (DXA), total body potassium (TBK), and BIS measurements were performed in 347 children (202 males and 145 females aged 4-18 y). The reference values for TBW, ECW, and ICW were defined by using a DXA+TBK model. BIS values were evaluated by using the method of Bland and Altman. A randomly selected calibration group (n = 231) was used to derive new BIS constants that were tested in the remaining group (n = 116). RESULTS: BIS values were highly correlated with the reference values (r(2) = 0.94-0.97, P < 0.0001), but differences between the BIS and DXA+TBK models for individuals were significant (P < 0.001). Use of new BIS constants reduced the mean differences between the BIS and DXA+TBK models; the SDs of the mean differences were improved (1.8 L for TBW, 1.4 L for ICW, and 1.0 L for ECW) for the total population. CONCLUSIONS: On a population basis, BIS can be calibrated to replace the DXA+TBK model for the assessment of TBW, ECW, and ICW in healthy children. The accuracy of the BIS measurement in individual children may be refined further by using age- and sex-specific adjustments for the BIS calibration constants.
Absorptiometry, Photon↗
Calcium absorption and kinetics are similar in 7- and 8-year-old Mexican-American and Caucasian girls despite hormonal differences.
To assess the possibility of ethnic differences in mineral metabolism in prepubertal children, we compared measures of calcium metabolism in 7- and 8-y-old Mexican-American (MA) and non-Hispanic Caucasian (CAU) girls (n = 38) living in southeastern Texas. We found similar fractional calcium absorption, urinary calcium excretion, calcium kinetic values and total-body bone mineral content in the MA and CAU girls. In contrast, parathyroid hormone (PTH) concentrations were greater in MA girls (4.01 +/- 0.47 vs. 1. 96 +/- 0.50 pmol/L, P = 0.005) than in CAU girls. Serum 25-hydroxyvitamin D concentrations were lower in MA girls (68.9 +/- 7.7 vs. 109.4 +/- 8.4 nmol/L, P = 0.001) than in CAU girls, but 1, 25-dihydroxyvitamin D concentrations did not differ between groups. Seasonal variability was seen for 25-hydroxyvitamin D concentrations in girls of both ethnic groups, but values in all of the girls were >30 nmol/L (12 ng/mL). We conclude the following: 1) greater PTH levels in MA girls than CAU girls are present without evidence of vitamin D deficiency; and 2) differences in 25-hydroxyvitamin D and PTH concentrations between MA and CAU girls do not have a large effect on calcium absorption, excretion or bone calcium kinetics. These data do not provide evidence for adjusting dietary recommendations for mineral or vitamin D intake by MA girls.
Absorption↗
Body composition as a clinical endpoint in the treatment of growth hormone deficiency.
Endpoints in the treatment and management of adults with growth hormone (GH) deficiency (GHD) can be problematic. Changes in body composition with recombinant human GH (rhGH) treatment may be one of the most objective measures that could be applied in judging the effectiveness and long-term efficacy. The relative strengths and weaknesses of measures of body composition and their potential for clinical utility in the setting of rhGH replacement in GHD in adults are discussed. Measurement of changes in body fat, regardless of the method employed, from pretreatment baseline through 2-6 months of treatment may be quite useful in demonstrating the efficacy of rhGH in each patient. Other changes in body composition are compromised by the imprecision of the measurements, shifts in extracellular water, and the small real changes which occur in bone and muscle in the GHD subject. Use of body composition measures of change in fat content as an endpoint in determining the efficacy of rhGH treatment in adults with GHD cannot be implemented on the basis of current data and would require a carefully designed prospective, controlled study. Until such criteria are established and accepted, endocrinologists must continue to manage these patients purely on the basis of their clinical judgment.
Adipose Tissue↗
Pubertal African-American girls expend less energy at rest and during physical activity than Caucasian girls.
Between 1963 and 1991, the most dramatic increases in the prevalence of overweight in the United States have been reported in African-American girls. Lower basal energy expenditure and lack of physical activity are believed to be risk factors for excessive weight gain. We hypothesized that energy expenditure at rest and during physical activity are lower in pubertal African-American girls than in Caucasian girls. Basal metabolic rate and sleeping energy expenditure of 40 Caucasian and 41 African-American pubertal girls (matched for age, physical characteristics, body fat, and energy intake) were measured by whole-room calorimetry, energy expended for physical activity by the doubly labeled water method, sexual maturity by physical examination, body composition by dual-energy x-ray absorptiometry, physical fitness by treadmill testing, and energy intake by 3-day food record. After adjusting for soft lean tissue mass, the basal energy expenditure (1333 +/- 132 vs. 1412 +/- 132 kcal/day, P = 0.01) and energy expended for physical activity (809 +/- 637 vs. 1271 +/- 162 kcal/day, P < 0.01) were significantly lower in the African-American girls than in the Caucasian girls. The differences remained the same after controlling for differences in sexual maturity and/or physical fitness. The lower energy expenditure of the pubertal African-American girls suggests that they are at a higher risk of becoming overweight than their Caucasian counterparts.
Adolescent↗
Vitamin D receptor gene Fok1 polymorphism predicts calcium absorption and bone mineral density in children.
The vitamin D receptor (VDR) gene has been implicated as one of the major genetic components of osteoporosis. We evaluated the relationship between markers of mineral status and restriction fragment length polymorphisms of the VDR gene in 72 healthy children age 7-12 years. Using stable isotope techniques and dual-energy X-ray absorptiometry, we measured dietary calcium absorption, bone calcium deposition rates, and total body bone mineral density (BMD). The Fok1 polymorphism at the VDR translation initiation site was significantly associated with BMD (p = 0.02) and calcium absorption (p = 0.04). Children who were FF homozygotes had a mean calcium absorption that was 41.5% greater than those who were ff homozygotes and 17% greater absorption than Ff heterozygotes. BMD was 8.2% greater in the FF genotype than the ff genotype and 4.8% higher than the Ff genotype. These results suggest a substantial relationship between the VDR gene and bone metabolism at one or more levels, including dietary absorption of calcium and BMD in growing children.
Absorptiometry, Photon↗
Lean body mass of well-nourished women is preserved during lactation.
To determine whether the lean body mass of well-nourished women was mobilized to support milk protein output during lactation, the body composition of 10 lactating and 10 nonlactating women was examined longitudinally at 6-wk intervals between 6 and 24 wk postpartum and at 52 wk postpartum, and that of 10 nulliparous women was examined at equivalent intervals, by using clinical anthropometry and whole-body potassium counting. Milk production was determined at 6-wk intervals during the period of exclusive breast-feeding (6-24 wk postpartum) by the test-weighing procedure. Milk composition was determined by chemical analysis. Dietary intakes were determined at 6-wk intervals between 6 and 24 wk postpartum from 3-d food records with use of a nutrient database. Lean body mass was maintained in women who exclusively breast-fed their infants during the first 6 mo postpartum while consuming dietary protein in amounts that exceeded those of their nonlactating counterparts by 55%. The high protein intakes were sustained throughout lactation despite a progressive reduction by 32% of milk protein output. Lean body mass was preserved throughout lactation in well-nourished women, suggesting that the metabolic needs of milk protein production were met solely by higher protein intakes of the lactating women.
Adipose Tissue↗
Human hydrometry: comparison of multifrequency bioelectrical impedance with 2H2O and bromine dilution.
The traditional method of assessing total body water (TBW), extracellular water (ECW), and intracellular water (ICW) has been the use of isotopes, on the basis of the dilution principle. Although the development of bioelectrical impedance techniques has eliminated many of the measurement constraints associated with the dilution methods, the degree of interchangeability between the two methods remains uncertain. We used multifrequency bioelectrical impedance spectroscopy (BIS), 2H2O dilution, and bromine dilution to assess TBW, ECW, and ICW in 469 healthy subjects (248 males, 221 females) aged 3-29 yr. We found that the TBW, ECW, and ICW estimates for the BIS and dilution methods were significantly correlated (r2 = 0.80-0.96, P < 0.0001, SE of the estimate = 2.3-2.7 liters). On the basis of population, the constants used in the BIS analysis could be adjusted so that the mean differences with the dilution methods would become zero. The SD values for the mean differences between the dilution and BIS methods, however, remained significant for both males and females: TBW (+/-2.1-2.8 liters), ECW (+/-1.4-1.6 liters), and ICW (2.0-3.1 liters). To improve the accuracy of the BIS measurement for an individual within the age range we have examined, further refinement of the constants used in the BIS analysis is needed.
Adolescent↗
Serum leptin concentrations in Caucasian and African-American girls.
Because African-American girls are heavier, taller, and mature earlier than Caucasian girls, we hypothesized that the serum leptin concentration differs between the two groups. Serum leptin concentrations were measured by immunoassay in 12-h fasted blood samples collected from 79 Caucasian and 57 African-American girls between 8 and 17 yr of age. Body composition was measured by dual-energy x-ray absorptiometry, sexual maturity by physical examination, and physical fitness by treadmill testing. Serum leptin concentrations were positively correlated (P < 0.01) with maturation, body fatness, and insulin and were higher (6.6 ng/mL, P < 0.01) in the African-American girls after adjusting for age. The difference remained significant (P < 0.01) but was reduced to 3.2 ng/mL after controlling for differences in maturation, fat mass, and physical fitness. The higher serum leptin levels might play an important role in the accelerated growth and sexual maturation of African-American girls.
Adolescent↗