Shumei S. Guo

Tracking of body mass index in children in relation to overweight in adulthood

Body mass index (BMI; in kg/m2) values at or above the 75th percentile are associated with increased morbidity and mortality in adulthood, and there are significant correlations between BMI values in childhood and in adulthood. The present study addresses the predictive value of childhood BMI for overweight at 35 +/- 5 y, defined as BMI >28 for men and BMI >26 for women. Analyses of data from 555 white children showed that overweight at age 35 y could be predicted from BMI at younger ages. The prediction is excellent at age 18 y, good at age 13 y, but only moderate at ages <13 y. For 18-y-olds with BMIs above the 60th percentile, the probability of overweight at age 35 y is 34% for men and 37% for women. A clinically applicable method is provided to assign an overweight child to a group with a known probability of high BMI values in adulthood.

Body composition estimates from NHANES III bioelectrical impedance data

BACKGROUND: Body composition estimates for the US population are important in order to analyze trends in obesity, sarcopenia and other weight-related health conditions. National body composition estimates have not previously been available.OBJECTIVE: To use transformed bioelectrical impedance analysis (BIA) data in sex-specific, multicomponent model-derived prediction formulae, to estimate total body water (TBW), fat-free mass (FFM), total body fat (TBF), and percentage body fat (%BF) using a nationally representative sample of the US population.DESIGN: Anthropometric and BIA data were from the third National Health and Nutrition Examination Survey (NHANES III; 1988–1994). Sex-specific BIA prediction equations developed for this study were applied to the NHANES data, and mean values for TBW, FFM, TBF and %BF were estimated for selected age, sex and racial-ethnic groups.RESULTS: Among the non-Hispanic white, non-Hispanic black, and Mexican-American participants aged 12–80 y examined in NHANES III, 15 912 had data available for weight, stature and BIA resistance measures. Males had higher mean TBW and FFM than did females, regardless of age or racial-ethnic status. Mean TBW and FFM increased from the adolescent years to mid-adulthood and declined in older adult age groups. Females had higher mean TBF and %BF estimates than males at each age group. Mean TBF also increased with older age groups to approximately 60 y of age after which it decreased.CONCLUSIONS: These mean body composition estimates for TBW, FFM, TBF and %BF based upon NHANES III BIA data provide a descriptive reference for non-Hispanic whites, non-Hispanic blacks and Mexican Americans in the US population.

Prediction of stature from knee height for black and white adults and children with application to mobility-impaired or handicapped persons

OBJECTIVE No adequate methods exist for predicting stature to help assess the growth of handicapped (including mobility-impaired) children or to help in developing indexes of obesity or equations for estimating basal energy expenditure for adults. In this project, equations were developed to predict stature in white and black adults and children from nationally representative samples for application to mobility-impaired and handicapped persons. SAMPLES Samples of healthy adults (n = 5,415) and children (n = 13,821) were selected from cycles I, II, and III of the National Health Examination Survey (NHES) conducted by the National Center for Health Statistics from 1960 to 1970. Balanced validation and cross-validation groups were created with regard to age, ethnic group, and sex. OUTCOME MEASURES The NHES is the only national survey that contains body measurements biologically appropriate for predicting stature. These measurements include stature, sitting height, knee height, and buttocks to knee length. STATISTICAL ANALYSIS Equations were computed from an all-possible-subsets of weighted regression procedure to select the predictor variables in the validation group based on the values of R2 and the root mean square error. RESULTS Knee height predicted stature for white and black men, but the predictor variables for white and black women were knee height and age. For predicting stature in children 6 to 18 years of age, the predictor variable was knee height for all children. APPLICATIONS The equations presented here were developed for use with mobility-impaired or handicapped persons, but the measurements were collected from ambulatory people by means of standard techniques. The use of recumbent anthropometric data from mobility-impaired or handicapped persons in the equations will expand the errors of prediction over those presented in this report. The standard error for a person is a guide to the range of probability within which a predicted value can occur.

Stature prediction equations for elderly non-Hispanic white, non-Hispanic black, and Mexican-American persons developed from NHANES III data.

OBJECTIVE To develop new, nationally representative equations to predict stature for racial/ethnic groups of the elderly population in the United States. DESIGN Anthropometric data for stature, knee height, and sitting height for adults aged 60 years or older were collected from a sample of persons in the third National Health and Nutrition Examination Survey (1988-1994), a national probability sample of the US population. SUBJECTS A gender- and racial/ethnic-stratified sample of 4,750 persons from the US population (1,369 non-Hispanic white men, 1,472 non-Hispanic white women, 474 non-Hispanic black men, 481 non-Hispanic black women, 497 Mexican-American men, 457 Mexican-American women) aged 60 years or older participated in this study. STATISTICAL ANALYSES Sampling weights were used to adjust the individual data to account for unequal probabilities of selection, nonresponse, and coverage errors so that all individual data used in these analyses represented national probability estimates. Regression analysis was performed to predict stature in each gender and ethnic group, and the results were cross-validated. RESULTS Stature prediction models using knee height and age and sitting height and age were evaluated for each gender and racial/ethnic group. The equations with knee height and age were selected on the basis of root mean square error and pure errors in cross-validation and on the accuracy and validity of measures of knee height over sitting height. Results of these regressions, including regression coefficients, standard errors of the coefficients, multiple correlation coefficients, root mean square error, and the standard error for the individual for the final equations, are presented. CONCLUSIONS New stature prediction equations using knee height and age are presented for non-Hispanic white, non-Hispanic black and Mexican-American elderly persons from current nationally representative data. These equations should be applied when a measure of stature cannot be obtained, for example, for persons with amputations of the leg, or with spinal curvature or who are confined to bed. Predicted stature values are acceptable surrogates in nutritional indexes.

Six-compartment body composition model: inter-method comparisons of total body fat measurement.

OBJECTIVE: To compare 16 currently used total body fat methods to a six-compartment criterion model based on in vivo neutron activation analysis.DESIGN: Observational, inter-method comparison study.SUBJECTS: Twenty-three healthy subjects (17 male and 6 female).MEASUREMENTS: Total body water (TBW) was measured by tritium dilution; body volume by underwater weighing (UWW); total body fat and bone mineral by dual-energy X-ray absorptiometry (DXA), total body potassium (TBK) by whole-body 40K counting; total body carbon, nitrogen, calcium, phosphorus, sodium and chlorine by in vivo neutron activation analysis; skinfolds/circumferences by anthropometry (Anth); and resistance by single-frequency bioimpedance analysis (BIA).RESULTS: The average of total body fat mass measurements by the six-compartment neutron activation model was 19.7±10.2 kg (mean±s.d.) and comparable estimates by other methods ranged from 17.4–24.3 kg. Although all 16 methods were highly correlated with the six-compartment criterion model, three groups emerged based on their comparative characteristics (technical error, coefficient of reliability, Bland-Altman analysis) relative to criterion fat estimates, in decreasing order of agreement: 1. multi-compartment model methods of Baumgartner (19.5±9.9 kg), Heymsfield (19.6±9.9 kg), Selinger (19.7±10.2 kg) and Siri-3C (19.6±9.9 kg); 2. DXA (20.0±10.8 kg), Pace-TBW (18.8±10.1 kg), Siri-2C (20.0±9.9 kg), and Brozek-UWW (19.4±9.2 kg) methods; and 3. Segal-BIA (17.4±7.2 kg), Forbes-TBN (21.8±10.5 kg), Durnin-Anth (22.1±9.5 kg), Forbes-TBK (22.9±11.9 kg), and Steinkamp-Anth (24.3±9.5 kg) methods.CONCLUSION: Relative to criterion fat estimates, body composition methods can be organized into three groups based on inter-method comparisons including technical error, coefficient of reliability and Bland-Altman analysis. These initial groupings may prove useful in establishing the clinical and research role of the many available fat estimation methods.

Age of puberty: Data from the United States of America

In an attempt to determine whether the secular trend toward an earlier onset of puberty has continued over recent decades in the United States of America, published reports concerning the age of attainment of pubertal events have been reviewed. Such reports are very limited and vary in both design and inclusive ages of study subjects. Among females, two recent large cross‐sectional studies indicate that fifty percent of females in the United States attain Tanner breast stage 2 at 9.5 to 9.7 years of age. This is younger than previously thought, although adequate earlier studies of girls in the United States are not available for comparison. These two studies also indicate that about 14% of girls attain Tanner stage 2 while 8 years of age; one study extends earlier reporting that about 6% exhibit onset of breast development while 7 years of age. There is no evidence that the age of menarche or the attainment of adult (Tanner 5) breast development has decreased over the past 30 years. The data also suggest an earlier onset of Tanner stage 2 pubic hair but no change in attainment of stage 5. Among males, pubic hair may be appearing at younger ages, but data are inadequate or too inconsistent to allow firm interpretation. The lack of standardization of genital criteria of pubertal onset in the male makes any conclusions regarding secular trends impossible. In summary, earlier secular trends over recent decades related to better health, improved nutrition or socio‐economic status, or any putative influence by endocrine disrupters cannot be verified.

Growth in weight, recumbent length, and head circumference for preterm low-birthweight infants during the first three years of life using gestation- adjusted ages

Data from 867 preterm low-birthweight participants in the Infant Health and Development Program (IHDP) were used to develop reference data for growth status at an age and for increments from term to 36 month gestation-adjusted age (GAA). Weight, length and head circumference were recorded at 4 month intervals in the first year and at 6 month intervals in the second and third years. Selected percentiles for values at an age (status values) and increments for age intervals are presented in graphs separately for VLBW infants (< or = 1500 g at birth) and for LBW infants (1501-2500 g at birth). Percentiles of weight increments are presented beginning shortly before term for 1 month intervals to 6 month GAA, for 2 month intervals to 12 month GAA, and for 3-month intervals to 36 month GAA. Percentiles for length and head circumference increments are presented from term to 6 months for 2-month intervals, and to 36 month GAA for 3 month intervals. Among LBW infants, boys, had larger status and increment values than girls (P < 0.05), but there were no significant sex-associated differences in VLBW infants for status or increments. The mean status values and increments in weight and head circumference of the LBW infants were larger than those of VLBW infants, but the differences in length were not significant.

Reference data on gains in weight and length during the first two years of life

Serial data from studies of infants at the University of Iowa and from the Fels Longitudinal Study were used to develop sex-specific percentiles for increments in weight and recumbent length for selected intervals during the first 24 months of life. Weight increments are presented for 1-month intervals from birth to 6 months, 2-month intervals from birth to 12 months, and 3-month intervals from birth to 24 months. Length increments are presented for 2-month intervals from birth to 6 months, and for 3-month intervals from birth to 24 months of age. Weights and lengths at the target ages were obtained for the Iowa data by simple interpolation, and for the Fels data by fitting families of three-parameter mathematical functions to the serial data from ages 1 to 24 months. The tabular presentations are based on the Iowa data from birth to 3 months of age, on the combined Iowa and Fels data from 3 to 6 months of age, and on the Fels data from 6 to 24 months of age. We believe that these reference data will be useful in screening for deviations from normal growth and may aid in early detection of failure to thrive or excessive weight gain during early life.

Pregnant adolescent and adult women have similarly low intakes of selected nutrients.

OBJECTIVE To examine the dietary intake of pregnant adolescents during the second and third trimester of pregnancy, and to compare their nutrient intake with that of pregnant adults. DESIGN Two 7-day food records (14 days) from subjects participating in a larger randomized clinical calcium trial: the first at 19 to 21 weeks and the second between 29 and 31 weeks gestation. Intake of energy and selected nutrients were calculated and compared with dietary standards. SUBJECTS/SETTING Fifty-nine pregnant adolescents and 97 pregnant adults recruited from prenatal clinics at a metropolitan university hospital. STATISTICAL ANALYSES Two sample t tests, equality of variances, and repeated measures (analysis of variance). RESULTS There was no difference in mean nutrient intakes between the second and third trimesters. Using two 7-day food records, we found mean intakes for energy, iron, zinc, calcium, magnesium, folate, and vitamins D and E to be below recommended standards in both groups. Other nutrients examined met or exceeded reference values. Total daily intakes for energy and 11 nutrients were significantly higher in the adolescent compared to the adult diets (P < .05). These differences were not evident when nutrient values were corrected for energy, indicating that increased energy intake in the teen-aged population was contributed by nutrient-dense foods. APPLICATIONS This study indicates the need for continued dietary monitoring of pregnant adolescents and pregnant adults, including nutrition guidance that stresses food sources of calcium, magnesium, zinc, iron, fiber, folate, and vitamins D and E, the nutrients found deficient in their diets.

Body size and fatness in young adults in relation to age at menarche

The relationships among age at menarche, body size, and body composition were considered in university students surveyed in 1970 (n = 342) and 1987 (n = 109). Recalled ages at menarche, stature, weight, and the triceps skinfold thickness were measured. Subjects ranged in age from 17.5 to 22.5 years in both surveys and were divided into four categories by age at menarche: before 12 years, 12.0 through 12.99 years, 13.0 through 13.99 years, and older than 14 years. In both the 1970 and 1987 surveys, later maturers had significantly more linear physiques than those experiencing menarche earlier. Late maturers also showed a tendency to lower values for the body mass index (BMI) and triceps skinfold compared with early maturers. Comparative data for women of the same age from the Fels Longitudinal Study (n = 234) showed similar findings. Women who reached menarche at ages older than 14 years were significantly taller than women with menarcheal ages less than 13 years. Women with menarcheal ages younger than 12 years were significantly heavier and had higher BMIs than those from any older menarcheal category. They also had significantly thicker triceps skinfolds than those with menarcheal ages older than 14 years.