The assessment of the body fat percentage by skinfold thickness measurements in childhood and young adolescence

The relationship of skinfold thicknesses to body density and of skinfold thicknesses to densitometrically determined body fat was evaluated in a group of 378 boys and girls, aged 7-20 years. According to their maturation level, they were divided into a prepubertal, a pubertal and a post-pubertal group. In each maturation group boys were older, had higher body-weights and body heights, higher body densities, lower percentage body fat, higher waist:hips ratios and higher trunk:total skinfolds ratios than girls. Body density in each maturation level could be quite precisely predicted by skinfold thicknesses. In prepubertal and pubertal boys and girls but not in post-pubertal boys and girls, age was also an important predicting variable for body density. The assessment of percentage body fat from skinfold thicknesses had a prediction error of 3-5%, which was highest in the prepubertal children. The prediction error is comparable to the prediction error of percentage body fat from skinfold thicknesses in adults, as reported in the literature. Only in post-pubertal boys and girls was the waist:hip ratio correlated with measures of body fatness. Moreover, only in the post-pubertal boys and in the pubertal and post-pubertal girls was the waist:hips ratio correlated with another measure of body fat distribution, the trunk:total skinfold ratio. The relative amount of internal body fat was found to be higher in the younger maturation groups. It is concluded that at younger ages the waist:hips ratio is a poor indicator of body fat distribution.     

Fetal programming of body dimensions and percentage body fat measured in prepubertal children with a 4-component model of body composition, dual-energy X-ray absorptiometry, deuterium dilution, densitometry, and skinfold thicknesses

BACKGROUND: Intrauterine programming of body composition [percentage body fat (%BF)] has been sparsely examined with multiple independent reference techniques in children. The effects on and consequences of body build (dimensions, mass, and length of body segments) are unclear. OBJECTIVE: The study examined whether percentage fat and relation of percentage fat to body mass index (BMI; in kg/m2) in prepubertal children are programmed during intrauterine development and are dependent on body build. It also aimed to examine the extent to which height can be predicted by parental height and birth weight. DESIGN: Eighty-five white children (44 boys, 41 girls; aged 6.5-9.1 y) had body composition measured with a 4-component model (n = 58), dual-energy X-ray absorptiometry (n = 84), deuterium dilution (n = 81), densitometry (n = 62), and skinfold thicknesses (n = 85). RESULTS: An increase in birth weight of 1 SD was associated with a decrease of 1.95% fat as measured by the 4-component model (P = 0.012) and 0.82-2.75% by the other techniques. These associations were independent of age, sex, socioeconomic status, physical activity, BMI, and body build. Body build did not decrease the strength of the associations. Birth weight was a significantly better predictor of height than was self-reported midparental height, accounting for 19.4% of the variability at 5 y of age and 10.3% at 7.8 y of age (17.8% and 8.8% of which were independent of parental height at these ages, respectively). CONCLUSIONS: Consistent trends across body-composition measurement techniques add strength to the suggestion that percentage fat in prepubertal children is programmed in utero (independently of body build and BMI). It also suggests birth weight is a better predictor of prepubertal height than is self-reported midparental height.     

Associations between prenatal and infancy weight gain and BMI, fat mass, and fat distribution in young adulthood: a prospective cohort study in males and females born very preterm

BACKGROUND: Increasing evidence indicates that adult body composition is associated with prenatal and infancy weight gain, but the relative importance of different time periods has not been elucidated. OBJECTIVE: The objective was to study the association between prenatal, early postnatal, and late infancy weight gain and body mass index (BMI), fat mass, and fat distribution in young adulthood. DESIGN: We included 403 men and women aged 19 y from a Dutch national prospective follow-up study who were born at <32 wk of gestation. BMI, waist circumference, and waist-to-hip ratio SD scores and subscapular-to-triceps ratio, percentage body fat, fat mass, and fat-free mass at age 19 y were studied in relation to birth weight SD scores, weight gain from preterm birth until 3 mo postterm (early postnatal weight gain), and weight gain from 3 mo until 1 y postterm (late infancy weight gain). RESULTS: Birth weight SD scores were positively associated with weight, height, BMI SD scores, and fat-free mass at age 19 y but not with fat mass, percentage body fat, or fat distribution. Early postnatal and late infancy weight gain were positively associated with adult height, weight, BMI, waist circumference SD scores, fat mass, fat-free mass, and percentage body fat but not with waist-to-hip ratio SD scores or subscapular-to-triceps ratio. CONCLUSIONS: In infants born very preterm, weight gain before 32 wk of gestation is positively associated with adult body size but not with body composition and fat distribution. More early postnatal and, to a lesser extent, late infancy weight gain are associated with higher BMI SD scores and percentage body fat and more abdominal fat at age 19 y.     

Energy intake, not energy output, is a determinant of body size in infants

BACKGROUND: It has been proposed that the primary determinants of body weight at 1 y of age are genetic background, as represented by parental obesity, and low total energy expenditure. OBJECTIVE: The objective was to determine the relative contributions of genetic background and energy intake and expenditure as determinants of body weight at 1 y of age. DESIGN: Forty infants of obese and 38 infants of lean mothers, half boys and half girls, were assessed at 3 mo of age for 10 risk factors for obesity: sex, risk group (obese or nonobese mothers), maternal and paternal body mass index, body weight, feeding mode (breast, bottle, or both), 3-d energy intake, nutritive sucking behavior during a test meal, total energy expenditure, sleeping energy expenditure, and interactions among them. RESULTS: The only difference between risk groups at baseline was that the high-risk group sucked more vigorously during the test meal. Four measures accounted for 62% of the variability in weight at 12 mo: 3-mo weight (41%, P = 0.0001), nutritive sucking behavior (9%, P = 0.0002), 3-d food intake (8%, P = 0.0002), and male sex (3%, P = 0.05). Food intake and sucking behavior at 3 mo accounted for similar amounts of variability in weight-for-length, body fat, fat-free mass, and skinfold thickness at 12 mo. Contrary to expectations, neither total nor sleeping energy expenditure at 3 mo nor maternal obesity contributed to measures of body size at 12 mo. CONCLUSIONS: Energy intake contributes significantly to measures of body weight and composition at 1 y of age; parental obesity and energy expenditure do not.     

Infant growth and later body composition: evidence from the 4-component model

BACKGROUND: Rapid weight gain in infancy is associated with higher body mass index in later life, but its relation with individual body-composition components remains unclear. OBJECTIVE: We aimed to investigate associations between weight gain during different periods in infancy and later fat mass (FM) and fat-free mass (FFM). DESIGN: Body composition was assessed by using the 4-component model, dual-energy X-ray absorptiometry, and anthropometry in 234 healthy UK children and adolescents (105 boys; x +/- SD age: 11.4 +/- 3.8 y). Early growth measurements were prospective in 52 subjects and retrospective in 182. Relative weight gain was calculated as change in SD score (SDS) during different periods. RESULTS: Relative weight gain from 0 to 3 mo and from 3 to 6 mo showed positive relations with childhood FM, waist circumference, and trunk FM that were equivalent to increases in FMI (FM/height(2)) of 0.24 SDS (95% CI: 0.04, 0.44) and 0.50 SDS (0.25, 0.75) per 1-SDS increase in early weight and that were comparable to the effect of current obesity risk factors. Relative weight gain from 0 to 3 mo was also positively associated with later FFMI (FFM/height(2)). Relative weight gain from 6 to 12 mo was not associated with later body composition. Associations were independent of birth weight, sex, puberty, physical activity, socioeconomic class, ethnicity, and parental body mass index. CONCLUSIONS: In this Western population, greater relative weight gain during early infancy was positively associated with later FM and central fat distribution and with FFM. Rapid weight gain in infancy may be a risk factor for later adiposity. Early infancy may provide an opportunity for interventions aimed at reducing later obesity risk.     

Puberty begins with a characteristic subcutaneous body fat mass in each sex

OBJECTIVE: To observe whether there exists a characteristic body fat mass at pubertal onset. DESIGN: Longitudinal clinical follow-up (between ages of 10 and 15 y) with an annual visit in a sample of 469 children. They were grouped according to age of purbertal onset: boys with pubertal onset at the ages of 11 (n=59), 12 (n=88), 13 n=89) and 14 y (n=46), and girls with pubertal onset at the age of 10 (n=68), 11 (n=66), 12 (n=37) and 13 (n=16). METHODS: Height, weight, upper arm circumference and four skinfold thicknesses were recorded annually. In boys testicular volume index was measured, and genital development was assessed on the Tanner scale; in girls mammary development was measured also using the Tanner scale. The sum of four skinfolds, body mass index, upper arm fat estimate and percentage body fat were calculated. RESULTS: Boys presented a positive relation between the age of pubertal onset and body mass index (P<0.001), which was not observed in girls. Body mass index thus varied according to the onset of puberty in boys (P<0.001), but not in girls. The sum of four skinfolds, the upper arm fat estimate index and the percentage of body fat mass did not differ according to age of pubertal onset either in girls (P=NS) or in boys (P=NS). The characteristic adiposity of the puberty onset is progressively acquired during the previous years in all the groups. CONCLUSIONS: Puberty seems to begin with a characteristic subcutaneous body fat mass that is independent of the age of onset. This study supports the hypothesis of a close link between maturation and the development of an energy store in the form of adipose tissue in both sexes.     

Associations between prenatal and postnatal growth and adult body size and composition

BACKGROUND: Adult body size and composition (ABSC) measures are associated with work capacity and productivity, reproductive performance, and chronic disease risk. Growth failure in early childhood may have important long-term consequences through its influence on ABSC. OBJECTIVE: We assessed associations between prenatal and postnatal growth (0-2 y of age) and ABSC. DESIGN: We included 267 singletons from a prospective study carried out between 1969 and 1977 in 4 ladino Guatemalan villages. We used data from that study and from a follow-up study conducted in 1998-1999 (when the subjects were 21-27 y of age) to determine associations of birth weight, length at 15 d of age, ponderal index, and length at 2 y of age with adult height, weight, fat-free mass (FFM), fat mass, percentage of body fat, and waist-to-hip ratio. Multivariate linear regression analyses with mixed models were carried out to account for sibling clustering. Two-stage least-squares analyses were used to separate specific effects of prenatal and postnatal growth. RESULTS: Birth weight, length at 15 d of age, and length at 2 y of age were positively associated with height, weight, and FFM in both sexes (P < 0.05). Prenatal growth and postnatal growth were equally important determinants of height, weight, and FFM. Weak positive associations of postnatal growth with adult fat mass and percentage of body fat were found in both sexes, whereas similar associations for prenatal growth were found in women only. Growth in early childhood was not related to waist-to-hip ratio. CONCLUSIONS: Growth retardation in early childhood was associated with shortness and less FFM in adulthood. Preventing growth failure in utero and preventing growth failure during the first 2 y of life are equally important for ABSC.     

The determination of subcutaneous body fat percentage by measuring skinfold thickness in teenagers in Turkey

Our aim in this study was to determine the body fat percentage of teenagers in Diyarbakir, a city in southeast Turkey. The study included 1118 children between the ages of 10 to 15. Basic anthropometric measurements including body-mass index (BMI) and skinfold thickness were taken. The skinfold thickness were measured with a Lange skinfold caliper. Fat mass percentage (FM %) was predicted by using skinfold thickness equations. Differences between boys and girls across age groups for weight, height, and BMI were found to be statistically significant (P < 0.0001). With respect to skinfold thickness in the 10-y-old group, the thickness at triceps and subscapular sites in girls was higher than those of boys. In the 12-y-old group, the thickness was found to be higher in girls than boys at the triceps, biceps, and subscapular sites. We found that an increase in skinfold thickness in the 13, 14, and 15-y-old groups was significantly higher among girls than boys and tended to increase with age. However, such a tendency was not shown in boys. This tendency was found only at the triceps site in 10, 12, and 13-y-old boys. In addition, the skinfold thickness at the biceps site was found to be greater in the 14-y-old boys. The body fat mass percent in girls, especially those older than age 13, was also increased.     

Rapid growth among term children whose birth weight was appropriate for gestational age has a longer lasting effect on body fat percentage than on body mass index

BACKGROUND: It is not clear whether and how rapid growth in infancy, a risk factor for later obesity, differentially affects growth and body-composition development throughout childhood in term children with an appropriate-for-gestational age (AGA) birth weight. OBJECTIVE: The aim was to examine the effect of rapid growth in infancy on body mass index SD score (BMI SDS) and body fat percentage (%BF) trajectories until age 7 y. DESIGN: This analysis included 206 (50.5% female) AGA term participants of the Dortmund Nutritional and Anthropometric Longitudinally Designed Study. Repeated anthropometric measurements were obtained between 0.5 and 7 y of age. RESULTS: Fifty-nine of the 206 children (28.6%) displayed rapid growth (an increase in SDS for weight of >0.67 between birth and age 2 y). From 6 mo of age, their growth trajectories diverged from normal growers, and by age 7 y they had a higher BMI, more fat mass, and a higher risk of overweight (odds ratio: 6.2; 95% CI: 2.4, 16.5; P = 0.0002). Multilevel model analyses showed that the differences in BMI were achieved within the first 2 y of life [beta (+/-SE) SDS: 1.22 +/- 0.13], after which they persisted at this level until the age of 7 y, whereas differences in %BF, which were also already discernible by age 2 y (1.52 +/- 0.34%), became progressively larger over the next 5 y (adjusted difference: 0.23 +/- 0.11%/y; P = 0.03). CONCLUSIONS: Rapid growth in infancy and early childhood results in an increased BMI and %BF throughout childhood and an increased risk of overweight at age 7 y among AGA children. Rapid growth in AGA children has a more pronounced effect on %BF than on BMI.     

Evaluation of body fat in fatter and leaner 10-y-old African American and white children: the Baton Rouge Children's Study

BACKGROUND: Only a few published studies in children used several methods to compare body fat in large groups of fatter and leaner multiethnic children. We hypothesized that the preferred methods of determining body fat may differ in children with larger compared with smaller amounts of body fat, in boys compared with girls, and in African Americans compared with whites. OBJECTIVE: Our objective was to evaluate several methods of predicting body fat in 10-12-y-old white and African American boys and girls. DESIGN: The body fat of 129 African American and white boys and girls aged 10-12 y, distributed equally by sex and race, was measured with use of dual-energy X-ray absorptiometry (DXA), underwater weighing (densitometry), isotope dilution (H(2)18O), bioelectrical impedance, skinfold thicknesses, corporal diameters, and circumferences. RESULTS: With use of DXA as the criterion variable, body fat was bimodally distributed in the boys and skewed to higher values in the girls. Biceps skinfold thickness had the highest predictive value of any single skinfold thickness compared with DXA fat. All formulas for estimating body fat from skinfold thicknesses, body density, or impedance performed better in the children in the upper one-half of the fat distribution (the fatter children) than in those in the lower one-half (the leaner children). Body mass index was highly correlated with body fat (R2 = 0.77); there was a good correlation for the fatter children (R2 = 0.66) and no correlation for the leaner children (R2 = 0.09). The hydration of the fat-free mass was significantly higher in the fatter children than in the leaner ones (79.2% compared with 76.7%). CONCLUSIONS: These data are consistent with the hypothesis that all methods of estimating body fat work better in children with larger amounts of body fat. The best formulas use skinfold thicknesses, bioelectrical impedance, and a 4-compartment model.     

Relationship between body composition and blood pressure in Bahraini adolescents

The objective of the present study was to examine the relationship between body composition and blood pressure (BP) in Bahraini adolescents. A sample of 504 Bahraini schoolchildren aged 12-17 years (249 boys and 255 girls) was selected using a multi-stage stratified sampling procedure. BP measurements were performed on the students. Anthropometric data including weight, height, waist circumference (WC), hip circumference, and triceps, subscapular and medial calf skinfold thicknesses were also collected. BMI, percentage body fat, waist:hip (WHR), and subscapular:triceps skinfold ratio were calculated. Mean systolic BP and mean diastolic BP were higher in males than in females. Weight and height in boys and weight only in girls were significantly associated with systolic BP independent of age or percentage fat. Nearly 14 % of the adolescents were classified as having high BP. BMI and percentage body fat were significantly and positively associated with the risk of having high BP in the boys and girls. Adolescents with high WHR or WC, as indicators for central obesity, tended to have higher BP values. The results from the present study indicate that obesity influences the BP of Bahraini adolescents and that simple anthropometric measurements such as WHR and WC are useful in identifying children at risk of developing high BP. These findings together with the known tracking of BP from adolescence into adulthood underline the importance of establishing intervention programmes in order to prevent the development of childhood and adolescent obesity.     

Adolescent skinfold thickness is a better predictor of high body fatness in adults than is body mass index: the Amsterdam Growth and Health Longitudinal Study

BACKGROUND: Body mass index (BMI) during adolescence is predictive of BMI at adult age. However, BMI cannot distinguish between lean and fat body mass. Skinfold thickness may be a better predictor of body fatness. OBJECTIVE: The objective of this study was to evaluate the relations between BMI and skinfold thickness during adolescence and body fatness during adulthood. DESIGN: We included 168 men and 182 women from the Amsterdam Growth and Health Longitudinal Study, a prospective study that conducted 8 measurements of BMI and skinfold thickness between 1976 and 2000. BMI and skinfold thickness during adolescence were analyzed in relation to adult body fatness measured at a mean age of 37 y with dual-energy X-ray absorptiometry. RESULTS: None of the boys and 1.7% of the girls were overweight at baseline, whereas the prevalence of high body fatness during adulthood was 29% in men and 32% in women. At the ages of 12-16 y, skinfold thickness was more strongly associated with adult body fatness than was BMI. Age-specific relative risks for a high level of adult body fatness varied between 2.3 and 4.0 in boys and between 2.1 and 4.3 in girls in the highest versus the lowest tertile of the sum of 4 skinfold thicknesses. For the highest tertile of BMI, the relative risk varied between 0.8 and 2.1 in boys and between 1.3 and 1.8 in girls. CONCLUSION: Skinfold thickness during adolescence is a better predictor of high body fatness during adulthood than is BMI during adolescence.     

Obesity prognosis: a longitudinal study of children from the age of 6 months to 9 years

The development of body fatness and leanness is examined in an ongoing prospective nutrition and growth study. Individual skinfold thicknesses, relative weights, weight gains, activity levels, and caloric intakes were examined at seven ages between 6 months and 9 years. Changes in body fatness in this group of children provide evidence that the obese infant usually does not become the obese child. Weight gain in infancy is also a poor predictor of 9-year old obesity. Changes from obese to non-obese or lean are often not linear. There is evidence that impending or actual obesity begins at ages 6 to 9 years with some predictability provided as early as age 2 years for girls, age 3 years for boys.     

Associations of birthweight and infant growth with body composition at age 15--the COMPASS study

Size at birth and postnatal growth have been positively associated with obesity in adulthood. However, associations between postnatal growth and body composition later in life have rarely been studied. The overall purpose was to explore the associations between birthweight, weight gain during first year of life and height, weight, body mass index, fat free mass index (FFMI), fat mass index, % fat mass (FM) and waist circumference in adolescence. The COMPASS study is a population-based study of adolescents from a well-defined area in Stockholm County, Sweden. Birth characteristics and weight during childhood were collected from registers and child health centre records, and body composition at age 15 years was measured by bioelectric impedance by trained nurses. Complete data were available for 2453 adolescents. Associations between predictor and outcome variables were assessed with linear regression modelling. Birthweight was positively associated with all outcome variables, except for %FM among girls. FFMI increased by 0.49 kg/m(2)[95% CI 0.34, 0.63] (boys) and 0.25 kg/m(2)[0.12, 0.38] (girls) per 1 SD increase in birthweight. Increased weight gain in infancy showed strong, positive associations with all measures of body composition. FFMI increased by 0.73 kg/m(2)[0.60, 0.87] (boys) and 0.63 kg/m(2)[0.50, 0.76] (girls) per unit increase in weight z-score during first year of life. The effect of increased weight gain in infancy was not modified by birthweight. Birthweight and postnatal growth were both positively related to body composition in adolescence. Increased weight gain during the first year of life had stronger effect than prenatal growth, suggesting infancy to be a more critical period.     

Upward weight percentile crossing in infancy and early childhood independently predicts fat mass in young adults: the Stockholm Weight Development Study (SWEDES)

BACKGROUND: Rapid early postnatal weight gain predicts increased subsequent obesity and related disease risks. However, the exact timing of adverse rapid postnatal weight gain is unclear. OBJECTIVE: The objective was to examine the associations between rapid weight gain in infancy and in early childhood in relation to body composition at age 17 y. DESIGN: This prospective cohort study was conducted in 248 (103 males) singletons and their mothers. Height and weight were measured at birth, 6 mo, and 3 and 6 y. The rates of weight gain during infancy (0-6 mo) and early childhood (3-6 y) were calculated as changes in sex- and age-adjusted weight SD scores during these time periods. At 17 y, body composition was measured by air-displacement plethysmography. RESULTS: Increasing weight gain during infancy and early childhood were both independently associated with larger body mass index, fat mass, relative fat mass, fat-free mass, and waist circumference at 17 y (P < 0.005 for all; adjusted for sex, birth weight, gestational age, current height, maternal socioeconomic status, and maternal fat mass). Rapid weight gain in infancy, but not in early childhood, also predicted taller height at 17 y (P < 0.001). CONCLUSIONS: Rapid weight gain in both infancy and early childhood is a risk factor for adult adiposity and obesity. Rapid weight gain in infancy also predicted taller adult height. We hypothesize that rapid weight gains in infancy and early childhood are different processes and may allow separate opportunities for early intervention against obesity risk later in life.     

Early programming of body composition and fat distribution in adolescents

Size at birth and early postnatal growth are determinants of adult height and BMI. The aim of this study was to evaluate the effect of birth weight on body composition and fat distribution in a group of Spanish adolescents. Current body composition was assessed by both skinfold thickness and dual X-ray absorptiometry in 234 adolescents born at term (140 girls and 94 boys), now aged 13-18 y and living in the city of Zaragoza. Relative fat distribution was estimated using the ratio of the subscapular to triceps skinfolds (S:T). Birth weight and gestational age were assessed by a questionnaire. Birth weight was inversely associated with the S:T ratio (P < 0.05) in boys and directly associated with bone mass (P < 0.01) and fat-free mass (P < 0.05) in girls. This association was independent of factors such as age, Tanner stage, gestational age, socioeconomic status, physical activity, and height. In conclusion, our data support the hypothesis that impaired fetal growth, measured by birth weight, may be related to central fat distribution in boys and decreased bone and fat-free mass in girls.     

Anthropometric indicators of body composition in young adults: relation to size at birth and serial measurements of body mass index in childhood in the New Delhi birth cohort

BACKGROUND: South Asians have a muscle-thin but adipose body phenotype and high rates of obesity-related disease. Adult body composition may be predictable in early life. OBJECTIVE: Anthropometric indexes of adult body composition were examined in relation to birth size and body mass index (BMI) during childhood. DESIGN: A population-based cohort of 1526 men and women aged 26-32 y in Delhi, India, who were measured sequentially from birth until 21 y of age were followed up. Adult weight, height, skinfold thicknesses, and waist and hip circumferences were measured. BMI and indexes of adiposity (sum of skinfold thicknesses), central adiposity (waist-hip ratio), and lean mass (residual values after adjustment of BMI for skinfold thicknesses and height) were derived. RESULTS: Mean birth weight was 2851 g. As children, many subjects were underweight-for-age (>2 SDs below the National Center for Health Statistics mean; 53% at 2 y), but as adults, 47% were overweight, 11% were obese, and 51% were centrally obese (according to World Health Organization criteria). Birth weight was positively related to adult lean mass (P < 0.001) and, in women only, to adiposity (P = 0.006) but was unrelated to central adiposity. BMI from birth to age 21 y was increasingly strongly positively correlated with all outcomes. BMI and BMI gain in infancy and early childhood were correlated more strongly with adult lean mass than with adiposity or central adiposity. Higher BMI and greater BMI gain in late childhood and adolescence were associated with increased adult adiposity and central adiposity. CONCLUSIONS: Birth weight and BMI gain during infancy and early childhood predict adult lean mass more strongly than adult adiposity. Greater BMI gain in late childhood and adolescence predicts increased adult adiposity.     

Sex-related influence of body size and sexual maturation on blood pressure in adolescents.

OBJECTIVE: This study is aimed at investigating the influence of body size, body fat and sexual maturation on blood pressure (BP) in adolescents. DESIGN: A cross-sectional study. SETTING: A suburban student population of Southern Italy. SUBJECTS: One hundred ninety students attending the first and second year of a secondary school. Five were excluded because they were affected by major diseases. The remaining were 98 M and 87 F (mean age for either group = 12.0+/-0.8 y). METHODS: Blood pressure was measured by a mercury sphygmomanometer, body weight by a platform beamscale, other measurements included height, biceps, triceps, subscapular and suprailiac skinfolds by a caliper; sexual maturation was evaluated according to Tanner. RESULTS: Body size was greater than in Tanner's population: in particular body weight (but not height) in our sample markedly exceeded that of the children of the same age in Tanner's population. Boys had higher systolic blood pressure (SBP) than girls (BP = 109/64+/-12/10 vs. 103/63+/-11/8 mm Hg, P<0.02 for SBP), while heart rate and waist/hip ratio were lower. During puberty evaluated on the basis of pubic hair growth BP in girls was higher than in the prepubertal phase (107/66+/-9/7 vs. 99/61+/-10/7, P<0.01). Pubertal boys showed a reduced percent of body fat (calculated from four skinfold measurements) in comparison to prepubertal ones (21.0%+/-4.5 vs. 24.5%+/-7.1, P<0.01). In linear correlation analysis, height, BW, BMI and lean body mass were found to be significantly associated with SBP in both sexes and to diastolic blood pressure (DBP) in girls. Percent body fat was correlated with SBP in boys, while sexual maturation was associated to SBP and DBP in girls only. Multiple regression analysis indicated a significant contribution of body size to BP variability, particularly in the girls. Sexual maturation was excluded from the final regression equations when height, BW or lean body mass were present. CONCLUSIONS: These data indicate that body weight in these adolescents is greater that in Tanner's population of the same age and sex. Body size appears to be a major determinant of BP, whereas sexual maturation seems to influence BP levels mainly through body growth. The influence of percent body fat on BP setting seems to be of limited importance.     

Prematurity and reduced body fatness at 8-12 y of age

BACKGROUND: Increasing evidence suggests that body composition, an important factor influencing morbidity and mortality in adult life, might be programmed by early growth and nutrition. Children born preterm remain shorter and lighter than their term-born peers during childhood, but it is unclear whether the size difference is associated with altered body composition. OBJECTIVE: We tested the hypothesis that both fat mass (FM) and fat-free mass (FFM) are proportionately lower in children born preterm than in children born at term. DESIGN: A total of 497 children born preterm and 95 children born at term were studied at 8-12 y of age. Body composition was determined with the use of skinfold thicknesses and dual-energy X-ray absorptiometry (in 200 preterm and 95 term children). FM and FFM were normalized for height to give fat mass index (FMI) and fat-free mass index (FFMI), respectively. RESULTS: Children born preterm were significantly lighter than those born at term and had lower FM and FFM. However, FMI was significantly lower in preterm children, whereas FFMI was not. FMI was also significantly lower in boys than in girls and in children with higher activity levels. Additional data available for the preterm group showed no association between birth weight, gestational age, or neonatal diet and later FMI or FFMI. CONCLUSIONS: The smaller size of children born preterm than of children born at term is associated with lower FM but not FFM when normalized for height. We hypothesize that this could result in a reduction in the risk of obesity and related diseases during adult life.     

Associations of size at birth and dual-energy X-ray absorptiometry measures of lean and fat mass at 9 to 10 y of age

BACKGROUND: Birth weight has been positively associated with risk of overweight in later life. However, little information exists on how weight and length at birth are associated with subsequent lean and total body fat. OBJECTIVE: We investigated the association between weight and length at birth and body composition and fat distribution in childhood. DESIGN: Body composition was measured by using dual-energy X-ray absorptiometry in 9-10-y-old subjects (n = 3006 boys and 3080 girls). Weight and length at birth were measured or taken from hospital records. RESULTS: Birth weight was positively associated with both lean body mass (LBM) and total body fat at 9-10 y of age in both sexes. LBM rose by 320 g per 1-SD increase in birth weight (P < 0.001), and total body fat rose by 2.5% (P = 0.001), but birth weight was unassociated with the fat-to-lean mass ratio (FLR). Ponderal index (PI) at birth (ie, weight/length3) was positively associated with LBM, total body fat, and the FLR in both sexes; the FLR increased by 2.7% in boys (P = 0.021) and by 5.0% in girls per 1-SD increase in PI (P < 0.001). Weight and length at birth did not predict central adiposity; although trunk fat had a strong positive association with PI at birth, this association disappeared after adjustment for total body fat. CONCLUSIONS: Higher PI at birth is associated with both higher fat and lean mass in childhood but also with an increase in the FLR. PI at birth is a better predictor of subsequent adiposity than is birth weight.