Itziar Salces

Comparison of predicted body fat percentage from anthropometric methods and from impedance in university students

The objective of the present study was to compare different methods for evaluating body fat percentage (BF%) (anthropometric methods and bioelectrical impedance analysis) in university students. Subjects were 653 healthy students whose mean age, body height, body weight and BMI were 21.1 (SD 2.5) years, 166.0 (SD 8.4) cm, 62.8 (SD 11.0) kg and 22.7 (SD 3.1) kg/m(2), respectively. Results showed that BMI is a poor predictor of body fatness since the sensitivity was low in comparison with the reference method (Siri equation). The lowest values of BF% were obtained using the reference method (Siri equation) (21.8 (SD 6.8)%). The two methods with the highest agreement were Siri and Lean (mean difference, -0.5), followed by Brozek (mean difference, -1.4) and Deurenberg (mean difference, -1.5). The largest mean difference for BF% was between Siri and impedance (-4.5). Although the methods and/or equations used in the present study have been commonly utilised to estimate BF% in young adults, the results must be interpreted with caution in the diagnosis and monitoring of overweight and obesity.

Overweight and Obesity: Prediction by Silhouettes in Young Adults

The present study analyzes the prevalence of overweight/obesity in a sample of young adults from the University of the Basque Country (Spain), and tests the efficiency of the silhouettes to predict overweight/obesity. This cross‐sectional study was conducted in a sample of volunteer university students from the University of the Basque Country (356 men and 745 women, age: 18–33 years), who came to the Physical Anthropology laboratory where a standardized questionnaire was administered and anthropometric measurements were taken by a well‐trained anthropometrist. Height and weight were obtained. BMI was calculated as weight/height2 (kg/m2) and it was used as a reference method. Using a questionnaire, based on the standard figural stimuli, subjects were asked to choose the silhouette which was closest to his/her usual appearance (current body size). The accuracy of the Williamson et al.s silhouettes as an overweight‐obesity indicator was analyzed by gender‐specific receiver operating curve (ROC). The cutoff figure to distinguish between nonoverweight and overweight‐obese individuals corresponded to number 7 in men and 6 in women. These cutoff values matched optimal sensitivity and specificity, with few nonoverweight subjects selecting silhouettes bigger than 7 in the case of men or 6 for women. In conclusion, the figural stimuli allows the identification of populations at overweight/obesity risk with the simple use of silhouettes, at least in this rank of age, where the overweight and obesity are yet little frequent.

Age variations in sibling correlations for height, sitting height and weight

Familial correlations for height, sitting height and weight have been studied in a sample of 1278 siblings for the Biscay province (Basque Country), aged 4+ to 24+ years. The data have been internally standardized according to sex and age of individuals. The degree of resemblance among sibling has been expressed by intraclass correlation coefficients. The total sample has been divided into three age categories: < 12 years, 12-15 years, and > or = 15 years, in order to examine the effect of age on sibling correlations. In general, changes with age have been observed: sibling correlations for height show a clear upward trend through the considered growth period, reaching a value of 0.48 from 15 years of age. Intra-correlations for weight show a slight downward trend with age. Sitting height shows a rather low correlation before 12 years of age, but equally high values in the other two ranges of age (0.48 and 0.47, respectively). This study confirms that the sibling resemblance for the analysed trait fluctuated through the growth period--height and sitting height showing similar patterns of variation with age--and that, after puberty, the degree of genetic determination is higher for bone measurements than for weight.

EVIDENCE OF PHENOTYPIC AND SOCIAL ASSORTATIVE MATING FOR ANTHROPOMETRIC AND PHYSIOLOGICAL TRAITS IN COUPLES FROM THE BASQUE COUNTRY (SPAIN)

This study examined 28 anthropometrical and physiological traits in 107 married couples living in the province of Biscay (Basque Country, Spain). The aim was to verify the existence of a phenotypic and/or social preference when choosing a mate. For this, correlations between pairs of spouses were estimated by maximum likelihood, and a model of familial transmission (path analysis) was applied in order to test if social homogamy between mates existed. The results provide significant evidence of phenotypic as well as social homogamy in several of the studied traits. Even if an assortment existed when choosing a mate for bony traits such as height, the effect of cohabitation cannot be discounted as the main causal factor for the high phenotypic resemblance observed between spouses for body composition traits. In addition, with the social homogeneity of the studied sample, significant evidence of the existence of social homogamy between mates was only found for 20% of the studied variables.

FAT DISTRIBUTION IN RELATION TO SEX AND SOCIOECONOMIC STATUS IN CHILDREN 4-19 YEARS

Fat distribution was studied in an urban sample of boys and girls 4.5 to 19.5 years from the Basque province of Biscay by means of Principal Component Analysis (PCA) of five skinfolds. The PCA extracted four components, which explained 99.1% of the total variance. The first principal component revealed strong stability across age and sex, and was related to a pattern of central body fat distribution. The three other components, upper‐lower trunk fat, lateral‐medial trunk fat, and upper‐lower extremity fat, showed poor stability due largely to the influence of age and, to a lesser degree, sex. In both sexes, individual scores of the four factors did not show multivariate differences by socioeconomic status when a MANOVA with age, age2 and age3 as covariates was done. Nevertheless, the first factor scores were significantly higher only in the poorer socioeconomic group of girls. The results are explained in the context of either different lifestyles related to socioeconomic status, a protective effect against environmental stress on urban males, or greater plasticity of trunk fat relative to extremity fat in females. Am. J. Hum. Biol. 10:799–806, 1998.

Sex differences in skinfold variability across human populations and during the life cycle.

Background: Subcutaneous fat measurements have been recently found to show sex differences in variability (dispersion dimorphism) in young adult samples from two extant unrelated European populations, with males more variable than females. Aim: This paper aims to investigate potential sex-by-age interaction and to verify its presence and possible different expression in various populations. Subjects and methods: Biceps, triceps, subscapular, suprailiac, abdominal, midthigh and calf skinfolds were analysed in two European samples from the Basque Country (4176 subjects, 8–50 years) and from Sardinia (2491 subjects, 14–100 years). Data on triceps and subscapular skinfolds in Non-Hispanic Whites (1799 subjects, 8–75 years), Mexican Americans (3133 subjects, 8–85 years), Other samples (1733 subjects, 8–70 years) from NHANES (2001–2002) were also included in the analysis. The significance of the difference between male and female coefficients of variation was performed by means of a suitable non-parametric bootstrap test. Results: Skinfold coefficients of variation were greater in males than in females in 79.8% of comparisons with 27.2% significant differences. Dispersion dimorphism was particularly evident in peripheral subcutaneous fat depots. The results do not show appreciable variations across population samples and age classes. Conclusion: Skinfold dispersion dimorphism seems to exist throughout most of the life cycle, and be widespread in European and non-European human populations. It involves especially accumulation sites of the gynoid pattern known to be relevant in female reproduction. More ‘standardized’ fatty reserves in women might represent a selective advantage. On the other hand, skinfold dispersion dimorphism might also be related to cultural factors affecting the extent of female variability by means of enhanced environmental homogeneity.

Age trends of sibling resemblance for height, weight and BMI during growth in a mixed longitudinal sample from Sarsuna-Barisha, India

Background: Even though some studies have considered that sibling resemblance remains constant throughout the life cycle, several investigations emphasize the importance of age and its interactions with genetic and environmental factors in determining sibling similarity in several bodily traits. In fact, the study of age changes in familial resemblance is of great importance for the analysis of certain sources of variation observed in growth processes. Aim: The study examined sibling resemblance for height, weight and body mass index (BMI) in a mixed longitudinal sample from West Bengal, ages 2–19 years, in order to analyse the variations with age of the sibling resemblance for these phenotypes during growth. Sample and methods: Two hundred and forty-five brothers and 213 sisters from 138 middle-class nuclear families living in a semi-urban area of South Kolkata, India were analysed. The analysis of sibling resemblance was performed through correlations estimated by the maximum-likelihood method. The patterns of different trends of sibling resemblance with age were examined by fitting a cubic non-linear regression to the observed correlations. Results: The results show clear variations with age in the sibling resemblance for the traits height and weight, though to a lesser extent for BMI. In general, we found the highest correlation values during the period of infancy, a remarkable decrease during puberty, and a trend of increase towards the end of the growth cycle. Conclusion: The study confirms the effect of age on the degree of similarity among siblings for height, weight and BMI in the sample. The sharp decline of correlation at adolescence can be interpreted in terms of the individual variation in age of reaching the adolescent growth spurt.

Heritability variations of body linearity and obesity indicators during growth.

Longitudinal as well as cross-sectional studies have shown variations with age in heritability estimates for body dimensions from infancy to adulthood, even though the patterns of variation are not completely clear. Further study on this subject is of great interest and may help obesity interventions for preventing or treating obesity in children. Therefore, the aim of the present study is to analyse the changes in the genetic and environmental architecture of 8 body linearity and obesity-related phenotypes during the growth process in a cross-sectional sample of 1018 nuclear families from the province of Biscay (Basque Country, Spain). The contribution of additive genetic effects to the variation of the analysed traits was estimated by a variance component analysis using the SOLAR program. Moderate to high heritability estimates were obtained for all 8 anthropometric phenotypes (38.23-65.98%). The heritability values show an increasing trend with age and in the course of the entire ontogenetic development two age periods were remarkable. At 7(+)-8(+) years of age a strong increase in heritability estimates was found for all the anthropometric phenotypes, except for the sum of skinfolds (SF6), reflecting the biological significance of genes during mid-childhood. During puberty, most of the obesity related phenotypes showed their highest heritability values while linear measurements and weight presented a decrease in the genetic contributions. In conclusion, this study confirms that additive genetic influences have a considerable effect on body linearity and obesity-related traits throughout the growth period and that mid-childhood and puberty are very sensitive periods in human life cycle.

Heritability variations of morphometric traits in West Bengal (India) children aged 4-19 years: a mixed-longitudinal growth study.

Background: Longitudinal and semi-longitudinal growth studies on siblings reflecting heritability changes during growth are very scarce. Moreover, studies of variables other than height, weight and BMI are virtually non-existent. Aim: The study compared changes in the heritability of six body lengths, four body breadths, and three indices between ages 4 and 19 years on the basis of a mixed-longitudinal sample of siblings, and examined whether heritability estimates change during the growth period. The data consisted of 238 brothers and 214 sisters from 134 middle-class nuclear families living in Kolkata (India). The analysis of sibling correlation was performed by maximum likelihood. The age-related patterns of heritabilities of the various traits were described by a cubic spline. Results: The heritability was very high and significant in most traits, and at all considered ages. Mean heritability in the 10 morphometric traits was 69.3%, which was higher than the heritability values for the three indices. Conclusions: These results confirmed the existence of age-related trends in heritability of the considered morphometric traits. The sharp decline of the heritabilities at adolescence in most of the morphometric traits, and the acromio-iliac index in particular, may be due to the large inter-individual variation in the age at which the adolescent growth spurt is reached in both sexes.

Family resemblance for anthropometric traits II. Assessment of maternal occupational and age effects

The present study was based on a cross-sectional sample of 1326 subjects (197 fathers, 466 mothers, 307 sons and 356 daughters) belonging to 488 nuclear families from the province of Biscay (Basque Country, Spain), with the purpose of estimating the degree of familial resemblance, for several anthropometric traits, by analysing the correlation coefficients between parent-offspring pairs. Height, weight, biacromial and bicrystal breadths, humerus and femur biepicondylar breadths, arm, waist and hip circumferences, biceps, triceps, subscapular, suprailiac, abdominal, thigh and calf skinfolds were taken from each individual. BMI, WHR and the sum of the seven skinfolds was computed. The mothers occupation and the age of offspring were taken into account, since the combination of all these factors might have an effect on familial resemblance. The mothers were classified into housewife (HM) and working mothers (WM). The offspring were divided into prepuberal, puberal and postpuberal subgroups. Standardised residuals were used to compute father-offspring (FO) and mother-offspring (MO) relations through correlation coefficients computed by maximum likelihood. The results confirm the influence of age on the correlations, since FO correlations revealed an increasing trend in HMs children for weight and another six variables as they grew older. On the other hand, the weight change tends to decrease with age in FO correlations within the WM group. Depending on mothers occupation and childrens age, the global trend in the sample results in higher correlations in the second group (WM) than in the first one (HM) for the whole age range, but specially in FO correlations before puberty, where four variables (weight, bicrystal breadth, triceps and subscapular skinfolds) yield statistically significant differences.