Ellen W. Demerath

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.

Puberty and Body Composition

Body composition during puberty is a marker of metabolic changes that occur during this period of growth and maturation, and, thus, holds key information regarding current and future health. During puberty, the main components of body composition (total body fat, lean body mass, bone mineral content) all increase, but considerable sexual dimorphism exists. Methods for measuring body composition (e.g. densitometry and dual-energy X-ray absorptiometry) and degree of maturity will be discussed in this review. Components of body composition show age-to-age correlations (i.e. ‘tracking’), especially from adolescence onwards. Furthermore, adipose tissue is endocrinologically active and is centrally involved in the interaction between adipocytokines, insulin and sex-steroid hormones, and thus influences cardiovascular and metabolic disease processes. In conclusion, pubertal body composition is important, not only for the assessment of contemporaneous nutritional status, but also for being linked directly to the possible onset of chronic disease later in life and is, therefore, useful for disease risk assessment and intervention early in life.

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.

The development of sex differences in digital formula from infancy in the Fels Longitudinal Study

Relative finger lengths, especially the second-to-fourth finger length ratio, have been proposed as useful markers for prenatal testosterone action. This claim partly depends on an association of relative finger lengths in adults with related sex differences in children and infants. This paper reports the results of a study using serial radiographs to test for both sex differences in the fingers of infants and children and for a relationship between sex differences in the children and infant finger and adult finger length ratios. This is the first study using long-term serial data to evaluate the validity of finger length ratios as markers. We found not only that sex differences in finger length ratios arise prior to puberty, but that sex differences in the fingers of children are highly correlated with adult finger length ratios. Our results strongly encourage the further use of finger length ratios as markers of perinatal testosterone action.

Anatomical Patterning of Visceral Adipose Tissue: Race, Sex, and Age Variation

Objective: We tested sex, race, and age differences in the patterning of visceral adipose tissue (VAT) and subcutaneous adipose tissue.

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.

The relationship of soluble ICAM-1, VCAM-1, P-selectin and E-selectin to cardiovascular disease risk factors in healthy men and women

Background : Clinical studies have shown that elevated serum concentrations of cell adhesion molecules such as inter-cellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), E-selectin (ESEL) and P-selectin (PSEL) may be independent risk factors for atherosclerosis and cardiovascular disease (CVD). Less is known of the relationship of these inflammatory markers with established CVD risk factors in healthy individuals, particularly women. Objective : The aim of this study was to examine cross-sectional relationships between the concentrations of soluble adhesion molecules (sICAM-1, sVCAM-1, sPSEL and sESEL) and smoking behaviour, body composition, blood pressure, serum lipids and physical activity in a large sample of healthy men and women, with special emphasis on interactions between smoking and other CVD risk factors. Subjects : The analysis included 592 healthy white adults aged 18-82 years. Results : There were no sex differences in the concentrations of sICAM-1, sVCAM-1 and sPSEL, but men had higher sESEL levels than women ( p < 0.0001). Male and female smokers had higher sICAM-1 and sESEL levels than non-smokers and soluble cell adhesion molecules (CAMs) were correlated with the pack-years of cigarette smoking ( r = 0.3 0.4, p < 0.0001, significant in women only). Significant independent associations were found between soluble CAMs and smoking, waist-hip ratio (WHR), blood pressure, high density lipoprotein cholesterol and total cholesterol. Furthermore, significant interaction effects were found in women, such that the relationship between CAMs and lipid concentrations and WHR were stronger in smokers than non-smokers. In conclusion, the concentration of soluble CAMs, particularly sICAM-1 and sESEL, reflect the level of established CVD risk factors in apparently healthy men and women, adding to the evidence that these factors contribute to CVD through their inflammatory effects on the vascular endothelium.

Validity of a new automated software program for visceral adipose tissue estimation

Introduction:Given the considerable time and research cost of analyzing biomedical images to quantify adipose tissue volumes, automated image analysis methods are highly desirable. Hippo Fat™ is a new software program designed to automatically quantify adipose tissue areas from magnetic resonance images without user inputs. Hippo Fat™ has yet to be independently validated against commonly used image analysis software programs.Objective:Our aim was to compare estimates of VAT (visceral adipose tissue) and SAT (subcutaneous adipose tissue) using the new Hippo Fat™ software against those from a widely used, validated, computer-assisted manual method (slice-O-matic version 4.2, Tomovision, Montreal, CA, USA) to assess its potential utility for large-scale studies.Methods:A Siemens Magnetom Vision 1.5-T whole-body scanner and a T1-weighted fast-spin echo pulse sequence were used to collect multiple, contiguous axial images of the abdomen from a sample of 40 healthy adults (20 men) aged 18–77 years of age, with mean body mass index of 29 kg/m2 (range=19–43 kg/m2).Results:Hippo Fat™ provided estimates of VAT and SAT that were highly correlated with estimates using slice-O-matic (R 2>0.9). Average VAT was 9.4% lower and average SAT was 3.7% higher using Hippo Fat™ compared to slice-O-matic; the overestimation of SAT tended to be greater among individuals with greater adiposity. Individual-level differences for VAT were also substantial; Hippo Fat™ gave estimates of VAT ranging from 1184 cm3 less to 566 cm3 more than estimates for the same person using slice-O-matic.Conclusion:Hippo Fat™ provides a rapid method of quantifying total VAT, although the method does not provide estimates that are interchangeable with slice-O-matic at either the group (mean) or individual level.

Quantitative genetic analysis of blood pressure reactivity to orthostatic tilt using principal components analysis

Blood pressure (BP) reactivity to orthostatic tilt may be predictive of cardiovascular disease. However, the genetic and environmental influences on BP reactivity to tilt have not been well examined. Identifying different influences on BP at rest and BP during tilt is complicated by the intercorrelation among multiple measurements. In this study, we use principal components analysis (PCA) to reduce multivariate BP data into components that are orthogonal. The objective of this study is to characterize and examine the genetic architecture of BP at rest and during head-up tilt (HUT). Specifically, we estimate the heritability of individual BP measures and three principal components (PC) derived from multiple BP measurements during HUT. Additionally, we estimate covariate effects on these traits. The study sample consisted of 444 individuals, distributed across four large families. HUT consisted of 70° head-up table tilting while strapped to a tilt table. BP reactivity (ΔBP) was defined as BP during HUT minus BP while supine. Three PC extracted from the PCA were interpreted as ‘general BP’ (PC1), ‘pulse pressure’ (PC2) and ‘BP reactivity’ (PC3). Variance components methods were used to estimate the heritabilities of resting BP, HUT BP, ΔBP, as well as the three BP PC. Significant (P<0.05) heritabilities were found for all BP measurements, except for systolic ΔBP at 1 and 3 min, and diastolic ΔBP at 2 min. Significant genetic effects were also found for the three PC. Each of these orthogonal components is significantly influenced by somewhat different sets of covariates.