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Objectives Studies from developed societies have shown that individuals with short legs relative to height have higher risk of type 2 diabetes. This has been much less explored in less developed populations where influences on relative leg length and diabetes may differ. The Brazilian Longitudinal Study of Adult Health (in Portuguese, ELSA-Brasil) allows us to test, in a cohort born (1934–1975) and raised when undernutrition was common, whether short legs relative to height is positively associated with diabetes, independent of early-life factors, including birth weight, age at menarche, and young-adult BMI. Methods We used baseline, cross-sectional data from 15,105 participants aged 35–74 years participating in ELSA-Brasil. We created age-and-sex-specific Z scores for leg length index (leg length/height × 100) according to an external reference. Diabetes was defined by self-reported physician diagnosis, medication use, fasting and 2-h post-75-g-load glucose, and A1C. Results A one-unit decrement in leg-length-index Z score was associated with 12% (8–17%) higher prevalence of diabetes in Brazilian adults, after adjustment through Poisson regression for confounders, including race, maternal education, and birth weight. This association persisted after further adjustment for menarche age, BMI (at age 20), buttocks circumference, and waist circumference. It was stronger among women with early menarche (P interaction = 0.02). Leg length index was also inversely associated with fasting glucose, fasting insulin, 2-h glucose, and A1C (P

Body composition assessment provides a sharper picture of the human biological response to genetic and environmental influences than measures of body size and weight. Infant body composition is particularly important as a marker of fetal adaptation and developmental programming of subsequent health and disease, but until recently, the range of options for measuring infant body composition was relatively narrow. The purpose of this Toolkit: Methods in Human Biology review is to provide a comprehensive overview of methods of body composition methods currently used in infants 0 to 2 years of age, including anthropometric prediction equations, air displacement plethysmography (ADP), dual energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA), isotope dilution, and magnetic resonance imaging (MRI). Information on the reliability, validity, and accuracy of the methods is provided. Unique aspects of infant physiology and behavior create challenges for body composition assessment, but this review provides guidance on suitable testing approaches and environments that may aid researchers in this important area of investigation.

Objectives There is biological crosstalk between insulin signaling and bone remodeling pathways, and wrist circumference and bone area were recently found to associate with insulin resistance independent of body mass index (BMI) in overweight/obese children. We aimed to expand on this work by using more specific measures of adiposity for adjustment and examining children with broader range of BMI. Methods We used serial data (1,051 total measures) on 313 non-Hispanic white youth (ages 8–18 y) from the Fels Longitudinal Study with homeostasis model assessment of insulin resistance (HOMA-IR) as the outcome. Internal standard deviation score (SDS) for wrist breadth was evaluated as a predictor of HOMA-IR (log-transformed) before and after adjusting for internal-sample SDSs for BMI, waist circumference (WC), and total body fat (TBF) from dual energy X-ray absorptiometry, in addition to age, sex, Tanner stage, and birth year, using generalized estimating equations. Results Before additional adiposity adjustment, we found a significant positive association between wrist breadth SDS and log-transformed HOMA-IR (β = 0.13; 95%CI: 0.09–0.17), which remained significant after adjusting for TBF SDS (β = 0.09; 95%CI: 0.05–0.13; P < 0.001), BMI SDS (β = 0.06; 95%CI: 0.02–0.10; P = 0.007), and WC SDS (β = 0.06; 95%CI: 0.02–0.09; P = 0.005). Conclusions Further work is needed to determine whether simple frame size measures such as wrist breadth may be useful markers of metabolic risk. Am. J. Hum. Biol., 25:581-585, 2013. © 2013 Wiley Periodicals, Inc.

Objectives To characterize an early trait in the BMI-for-age curve, the infant BMI peak. Methods BMI-for-age curves were produced for 747 non-Hispanic, white Fels Longitudinal Study participants, from which individual age (AgePeak) and BMI (BMIPeak) at maximum infant BMI were estimated. Multivariable general linear regression was used to examine the effects of sex and birth year cohort (1929–1950, 1951–1970, and 1971–2010) on AgePeak and BMIPeak, with associations between BMIPeak and concurrent sum of four skinfold thicknesses assessed in a subsample (N = 155). Heritability (h2) of AgePeak and BMIPeak was estimated using maximum-likelihood variance components analysis. Results AgePeak occurred at 9 months of age in both sexes, but BMIPeak was 0.4 kg/m2 higher for boys than for girls (P-value

Objective: To examine ethnic differences in adiposity at a given body mass index (BMI) in a sample of U.S.-born African-American and East African immigrant adolescent girls. Methods: In a sample of black adolescent girls (n = 79; ages 14–20) we compared measures of adiposity across the range of BMI-for-age among 55 U.S.-born African-American (mean BMI: 30.4; age: 15.4) and 24 East African immigrant girls (mean BMI: 21.8; age: 16.7). Fat and fat-free mass were assessed with dual-energy X-ray absorptiometry (DXA). We used spline regression to examine the distributions of fat mass index and percent body fat across the range of BMI-for-age z-scores. Results: Compared with African-American girls, East African girls were smaller on all body measures, but appeared to have higher fat mass index and percent body fat at the same BMI-for-age. Conclusions: Our findings indicate that at a given BMI East African immigrants may have greater adiposity than African-American girls. If corroborated in larger samples, our data suggest that the cardiometabolic risks attendant to elevated adiposity may affect East African girls at a lower BMI than in African-American girls. Am. J. Hum. Biol., 2011. © 2011 Wiley-Liss, Inc.

Obesity and height are generally unassociated in adults. However, in children, previous research consistently finds a positive association between obesity and height(Bruch, 1939; Freedman et al., 2004a; Freedman et al., 2004b; Stovitz et al., 2008). Longitudinal studies in generally well-nourished populations such as the U.S. and Sweden have found greater child height, particularly early childhood height, to be associated with adult obesity(Freedman et al., 2002; Freedman et al., 2005; He and Karlberg, 2001; Stovitz et al., 2010). Childhood obesity is associated with earlier pubertal maturation, especially in girls(Aksglaede et al., 2009; Biro et al., 2010; Buyken et al., 2009; Himes et al., 2004; Karlberg, 2002; Must et al., 2005; Sandhu et al., 2006; Wang, 2002), and more advanced pubertal development is, in turn, associated with diminished subsequent growth in height and a greater risk for young adult obesity(De Simone et al., 1995; Freedman et al., 2004a; He and Karlberg, 2001; Mamun et al., 2009; Rzehak and Heinrich, 2006). Thus, it is clear that height growth, even in well-nourished populations, does not occur in isolation from the child’s nutritional status and is accelerated by obesity. However, this association generally remains under-recognized by pediatricians and parents who may perceive elevated height in the overweight child as a sign that, with time, the child will “grow out of” their overweight condition. A clearer understanding of the childhood growth characteristics of overweight and obese young adults will help pediatricians assess the risk for future obesity in the child who is relatively tall or short. The purpose of the current investigation is to better understand the complex relationship of height growth and young adult obesity status. Using a large longitudinal cohort from four distinct areas of the U.S., we will examine differences in height growth between those who were overweight or obese by early adulthood as compared to those who were normal weight. The longitudinal approach allows us to study in detail the magnitude and timing of differences in height growth curves across the adult weight classification groups. Based on past research, we anticipate that those who become overweight or obese as young adults will have been relatively taller in early childhood, and then will have had slower growth in height with advancing age. In this study, we also examine the degree to which differences in height growth can be explained by variation in childhood subcutaneous fat thickness in an attempt to separate the effects of current fatness in childhood from subsequent obesity status as a young adult.

Objectives—To assess the relationship between telomere length and adiposity, using dualenergy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI), in addition to conventional anthropometric proxies including body mass index (BMI) and cardiovascular disease risk factors. Methods—A cross-sectional sample of 309 non-Hispanic white participants in the Fels Longitudinal Study aged 8 to 80 yr (52% female) was included. Average telomere length was measured by quantitative PCR. Results—Telomere length was negatively correlated with age (r = −0.32, P < 0.0001) and had numerous significant correlations with established cardiovascular disease risk factors including waist circumference (r = −0.33), apolipoprotein B (r = −0.26), systolic blood pressure (r = −0.28), and fasting serum glucose (r = −0.15); all P < 0.0025. In back-ward selection linear regression models of telomere length, adiposity measures were consistently retained in the best models; BMI, waist circumference, hip circumference, total body fat, and visceral adipose tissue volume were all inversely associated with telomere length at the nominal P < 0.05 level or lower, independent of age, sex, systolic blood pressure, and fasting serum lipid, lipoprotein, and glucose concentrations. The negative association of BMI with telomere length was stronger among younger than older participants (P for interaction, 0.03). Conclusions—Individuals with higher total and abdominal adiposity have lower telomere length, a marker of cellular senescence, suggesting obesity may hasten the aging process. Longitudinal studies are required to establish the causal association of early life adiposity with biological aging. Telomeres are noncoding repeat sequences at the ends of chromosomes [5′-(TTAGGG)n–3′] that function to stabilize the chromosome during mitosis, prevent aberrant recombination, and protect the chromosomes from end-degrading enzymes (Moyzis et al., 1988). In somatic cells, telomere repeats are lost at each cell division due to the inability of DNA polymerase to fully replicate chromosome ends (Levy et al., 1992; Olovnikov, 1973), leading to declines in telomere length with age. When telomere length reaches a critically short length in one or more chromosomes (the “Hayflick limit”), the cell is signaled to arrest replication and

Despite significant progress in understanding the mechanisms by which the prenatal/maternal environment can alter development and adult health, genetic influences on normal variation in growth are little understood. This work examines genetic and nongenetic contributions to body weight and weight change during infancy and the relationships between weight change and adult body composition. The dataset included 501 white infants in 164 nuclear and extended families in the Fels Longitudinal Study, each with 10 serial measures of weight from birth to age 3 years and 232 with body composition data in mid-adulthood. Herit-ability and covariate effects on weight and weight z-score change from birth to 2 years of age were estimated using a maximum likelihood variance decomposition method. Additive genetic effects explained a high proportion of the variance in infant weight status (h2 = 0.61–0.95), and change in weight z-score (h2 = 0.56–0.82). Covariate effects explained 27% of the phenotypic variance at 0–1 month of age and declined in effect to 6.9% of phenotypic variance by 36 months. Significant sex, gestational age, birth order, birth year, and maternal body mass index effects were also identified. For both sexes, a significant increase in weight z-score (>2 SD units) (upward centile crossing) was associated with greater adulthood stature, fat mass, and percent body fat than decrease or stability in weight z-score. Understanding genetic influences on growth rate in a well-nourished, nutritionally stable population may help us interpret the causes and consequences of centile crossing in nutritionally compromised contexts.

Objective. To evaluate the effects of habitual physical activity (PA) on the metabolic syndrome (MS) in young adult men and women. Research methods and procedures. Cross-sectional PA data were utilized from 249 women and 237 men, aged 18–40 years in the Fels Longitudinal Study. MS components—abdominal circumference (AC), triglycerides (TG), HDL, blood pressure (BP), and fasting glucose (FG)—were dichotomized according to the National Cholesterol Education Program's Adult Treatment Panel III revised criteria. Leisure, sport, work, and total PA scores were calculated using the Baecke Questionnaire of Habitual Physical Activity. Multiple logistic regression modeling assessed the effects of PA, age, smoking, and BMI on MS status. Results. 26.9% of men and 19.3% of women had MS. For men, MS risk was reduced with increases in both total PA [OR = 0.65 (95% CI: 0.47, 0.90)] and sport PA [OR = 0.40 (95% CI: 0.23, 0.70)]. AC, TG, and HDL values also improved with total and sport PA. Among women, the risk for MS was marginally reduced by total PA [OR = 0.72 (95% CI: 0.50, 1.02)] and HDL levels were increased by both total PA [OR = 0.79 (95% CI: 0.63, 0.98)] and sport PA [OR = 0.54 (95% CI: 0.35, 0.84)]. Discussion. Increased total and sport PA reduces risk for the MS in young men, though not as clearly in young women. Am. J. Hum. Biol. 19:544–550, 2007. © 2007 Wiley-Liss, Inc.

A number of recent reports suggest that the average age at menarche of US girls has declined over the past 20 years. Because the putative declines in the age at menarche are concurrent with increases in childhood body mass index (BMI), it has been suggested that these two trends may be causally linked. We examined differences in mean age of menarche in Fels Longitudinal Study girls who were born in six 10-year birth cohorts (1930s, 1940s, 1950s, 1960s, 1970s, and 1980s) and simultaneous cohort changes in mean BMI measured cross-sectionally at selected ages from 3-35 years (n = 371). Girls born in the 1980s had a mean age at menarche of 12.34 years, which was approximately 3-6 months earlier than that of girls born previously (P < 0.001). While the mean BMI values at ages 25 and 35 generally increased from the 1930s to the 1970s, the mean BMI during childhood and adolescence remained constant across the six birth cohorts. In summary, we found no evidence that the recent decline in the age at menarche in the Fels Longitudinal Study girls was reflected in concurrent increases in BMI at any point in childhood or adolescence. Conversely, girls born in the 1960s and 1970s have subsequently become heavier in young and mid-adulthood than were girls from earlier birth cohorts, without any concurrent change in the mean age at menarche over that time period. These two findings suggest that population-level shifts in BMI and the timing of menarche are largely independent, although sometimes coincident, processes.