Wm. Cameron Chumlea

SARCOPENIA: ITS ASSESSMENT, ETIOLOGY, PATHOGENESIS, CONSEQUENCES AND FUTURE PERSPECTIVES

Sarcopenia is a loss of muscle protein mass and loss of muscle function. It occurs with increasing age, being a major component in the development of frailty. Current knowledge on its assessment, etiology, pathogenesis, consequences and future perspectives are reported in the present review. On-going and future clinical trials on sarcopenia may radically change our preventive and therapeutic approaches of mobility disability in older people.

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.

Body mass index during childhood, adolescence and young adulthood in relation to adult overweight and adiposity: the Fels Longitudinal Study.

BACKGROUND: Childhood overweight develops during ‘critical periods’, but the relationship of body mass index (BMI) patterns during ‘critical periods’ from childhood into adulthood with subsequent overweight and adiposity has not been previously investigated. BMI patterns during early childhood, pubescence and post-pubescence and their independent effects on overweight and body fatness at 35–45 y of age were examined along with birth weight and the effects of adult lifestyle factors.METHODS: BMI parameters describing the timing, velocity minimum (min) and maximum (max) values from 2 to 25 y of age were related to adulthood BMI values and total and percentage body fat (TBF, %BF) at 35–45 y. These data were from 180 males and 158 females in the Fels Longitudinal Study.RESULTS: There was no sex difference in the timing of BMI rebound, but the age of BMI maximum velocity and maximum BMI were both earlier in girls. Children with an earlier BMI rebound had larger BMI values at rebound and at maximum velocity. Children who reached maximum BMI at later age had larger maximum BMI values. Maximum BMI was a strong predictor for adult BMI and in females, a strong predictor of adulthood TBF and %BF. Maximum BMI was closely related to maximum BMI velocity in females and in males, BMI at maximum velocity is a strong predictor of TBF and %BF.CONCLUSIONS: Changes in childhood BMI were related to adult overweight and adiposity more so in females than males. BMI rebound is a significant important period related to overweight at 35–45 y in females but not in males. However BMI patterns during and post-adolescence were more important than the BMI rebound for adulthood TBF and %BF status. There is marked tracking in BMI from approximately 20 y into 35–45 y. The pattern of BMI changes from 2 to 25 y had stronger effects on subsequent adult overweight than birth weight and adult lifestyle variables.

Do Changes in Body Mass Index Percentile Reflect Changes in Body Composition in Children? Data From the Fels Longitudinal Study

OBJECTIVE. Our aim was to examine the degree to which changes in BMI percentile reflect changes in body fat and lean body mass during childhood and how age and gender affect these relationships. METHODS. This analysis used serial data on 494 white boys and girls who were aged 8 to 18 years and participating in the Fels Longitudinal Study (total 2319 observations). Total body fat (TBF), total body fat-free mass (FFM), and percentage of body fat (%BF) were determined by hydrodensitometry, and then BMI was partitioned into its fat and fat-free components: fat mass index (FMI) and FFM index (FFMI). We calculated predicted changes (Δ) in FMI, FFMI, and %BF for each 10-unit increase in BMI percentile using mixed-effects models. RESULTS. FFMI had a linear relationship with BMI percentile, whereas FMI and %BF tended to increase dramatically only at higher BMI percentiles. Gender and age had significant effects on the relationship between BMI percentile and FFMI, FMI, and %BF. Predicted Δ%BF for boys 13 to 18 years of age was negative, suggesting loss of relative fatness for each 10-unit increase in BMI percentile. CONCLUSIONS. In this longitudinal study of white children, FFMI consistently increased with BMI percentile, whereas FMI and %BF had more complicated relationships with BMI percentile depending on gender, age, and whether BMI percentile was high or low. Our results suggest that BMI percentile changes may not accurately reflect changes in adiposity in children over time, particularly among male adolescents and children of lower BMI.

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.

Age- and maturity-related changes in body composition during adolescence into adulthood: The Fels Longitudinal Study

OBJECTIVES: To examine patterns of change in total body fat (TBF), percent body fat (%BF), and fat-free mass (FFM), from 8--20 y of age and the effect of rate of skeletal maturation. To determine the degree of tracking of body composition for individuals from childhood into adulthood.RESEARCH DESIGN: Annual serial data for TBF, %BF and FFM from underwater weighing using a multicomponent body composition model were collected from 130 CAUcasian males and 114 CAUcasian females between 1976 and 1996. Rate of maturation was defined as FELS skeletal age (SA) less chronological age (CA). Random effects models were used to evaluate general patterns of change and tracking of individual serial data over the 12 y age range.RESULTS: Changes in TBF followed a quadratic model for males and for females with declining rates of change. Changes for %BF followed a cubic model for males and females. General patterns of change for FFM followed a cubic model for males and a quadratic model for females. TBF for males and females increased with age, but the rates of change declined with age. %BF for females increased from age 8–20 y. For males, %BF increased with age, but the positive rates of change declined and became a negative when aged about 13 y and reached a minimum at about the age of 15 y. The rate of change for %BF increased thereafter. FFM for males and females increased with age, but the rates of change decreased with age. The extent of tracking is inversely related to the length of the time interval. At the same age, rapidly-maturing children have significantly larger amounts of TBF, %BF and FFM than slow-maturing children. Tracking in body composition for individuals persisted from childhood to adulthood.CONCLUSIONS: (1) There are gender-associated differences in these patterns of change for %BF and FFM but not for TBF; (2) TBF, %BF and FFM increased with increased rates of maturation; (3) significant tracking in body composition for individuals persists from childhood to adulthood.

Comparison of percent body fat estimates using air displacement plethysmography and hydrodensitometry in adults and children.

PURPOSE: The purpose of the study was to compare estimates of body density and percentage body fat from air displacement plethysmography (ADP) to those from hydrodensitometry (HD) in adults and children and to provide a review of similar recent studies.METHODS: Body density and percentage body fat (% BF) were assessed by ADP and HD on the same day in 87 adults aged 18–69 y (41 males and 46 females) and 39 children aged 8–17 y (19 males and 20 females). Differences between measured and predicted thoracic gas volumes determined during the ADP procedure and the resultant effects of those differences on body composition estimates were also compared. In a subset of 50 individuals (31 adults and 19 children), reliability of ADP was measured and the relative ease or difficulty of ADP and HD were probed with a questionnaire.RESULTS: The coefficient of reliability between %BF on day 1 and day 2 was 96.4 in adults and 90.1 in children, and the technical error of measurement of 1.6% in adults and 1.8% in children. Using a predicted rather than a measured thoracic gas volume did not significantly affect percentage body fat estimates in adults, but resulted in overestimates of percentage body fat in children. Mean percentage body fat from ADP was higher than percentage body fat from HD, although this was statistically significant only in adults (29.3 vs 27.7%, P<0.05). The 95% confidence interval of the between-method differences for all subjects was −7 to +9% body fat, and the root mean square error (r.m.s.e.) was approximately 4% body fat. In the subset of individuals who were asked to compare the two methods, 46 out of 50 (92%) indicated that they preferred the ADP to HD.CONCLUSION: ADP is a reliable method of measuring body composition that subjects found preferable to underwater weighing. However, as shown here and in most other studies, there are differences in percentage body fat estimates assessed by the two methods, perhaps related to body size, age or other factors, that are sufficient to preclude ADP from being used interchangeably with underwater weighing on an individual basis.

Serum leptin concentration, body composition, and gonadal hormones during puberty

BACKGROUND: Recent evidence has suggested that leptin concentration is associated with gonadal hormone levels, and that changes in leptin concentration may trigger the onset of reproductive function in children. However, the concurrent changes in body composition during puberty make the independent associations between leptin and gonadal hormone concentrations in children difficult to resolve.METHODS: To investigate the nature of associations between leptin levels and pubertal maturation, serum concentrations of leptin, estradiol, and testosterone and body composition measures were examined in a sample of 152 healthy pre-pubertal, pubertal, and post-pubertal children.RESULTS: Leptin concentration was nearly three-fold higher in post-pubertal girls than in pre-pubertal girls, but was relatively similar in pre- and post-pubertal boys. Significant sex differences in leptin concentration existed in pre-pubertal, pubertal and post-pubertal children, and these remained significant after controlling for adiposity. After adjusting for total body fat, fat-free mass and age, testosterone concentration was negatively associated with leptin levels in pubertal boys, while estradiol concentration was positively associated with leptin level in pubertal girls.CONCLUSIONS: Girls have higher serum leptin concentration before, during, and after puberty than boys, even after accounting for the development of greater female adiposity. Although other factors may be involved, sexual dimorphism in leptin concentrations during puberty appears to be partly due to a stimulatory effect of estradiol on leptin concentration in females and a suppressive effect of testosterone on leptin concentration in males.

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.

Body Composition Methods: Comparisons and Interpretation

The incidence of obesity in the United States and other developed countries is epidemic. Because the prevalence of comorbidities to obesity, such as type 2 diabetes, has also increased, it is clear there is a great need to monitor and treat obesity and its comorbidities. Body composition assessments vary in precision and in the target tissue of interest. The most common assessments are anthropometric and include weight, stature, abdominal circumference, and skinfold measurements. More complex methods include bioelectrical impedance, dual-energy X-ray absorptiometry, body density, and total body water estimates. There is no single universally recommended method for body composition assessment in the obese, but each modality has benefits and drawbacks. We present here the most common methods and provide guidelines by way of examples to assist the clinician/researcher in choosing methods appropriate to their situation.