Waist circumference in relation to body perception reported by Finnish adolescent girls and their mothers

Transcription

1 Acta Pædiatrica ISSN REGULAR ARTICLE Waist circumference in relation to body perception reported by Finnish adolescent girls and their mothers JS van Vliet 1, E Allansson Kjölhede 1,KDuchén 1,LRäsänen 2, N Nelson 1 1.Department of Clinical and Experimental Medicine, Division of Pediatrics, Faculty of Health Sciences, Linköping University, Sweden 2.Department of Applied Chemistry and Microbiology, Division of Nutrition, University of Helsinki, Finland Keywords Adolescent girls, Body mass index, Body perception, Maternal perception, Waist circumference Correspondence JS. van Vliet, Faculty of Health Sciences, Department of Clinical and Experimental Medicine, Division of Pediatrics, Linköping University, SE Linköping, Sweden. Tel: jolanda.van.vliet@lio.se Received 19 December 2007; revised 23 July 2008; accepted 8 October DOI: /j x Abstract Aim: To study how waist circumference (WC) relates to body perception in adolescent girls and to maternal perception of the girl s body size. Methods: Three hundred and four girls, years, were measured for height, weight and WC. 294 girls provided self-report data on weight, height and body image before anthropometric measurements. Paired data from 237 girls and mothers on perception of the girls body size were collected. Results: In girls, self-reported weight indicated awareness of actual body size. The girls body perception showed an overestimation of body size relative to international reference values for body mass index (BMI) (p < 0.05), but not for WC. Girls body perception exceeded that of their mothers (p < 0.05). Maternal perception agreed better than the girls perception with international reference values for BMI (p < 0.05). No significant difference between mothers and girls were found concerning agreement of body perception with international reference values for WC. Conclusion: WC rather than BMI agrees with perception of body size, possibly due to its relation to abdominal fat at different ages. For effective prevention and treatment programmes for weight-related health problems among adolescent girls, we recommend measuring WC to diminish the discrepancy between measured and perceived body size. INTRODUCTION The prevalence of overweight and obesity among children and adolescents is increasing worldwide (1). In Finland, between 1977 and 1999 the age-standardized prevalence of overweight increased from 7.2 to 16.7% in boys and from 4.0 to 9.8% in girls. The prevalence of obesity in boys was 1.1% in 1977 and 2.7% in 1999; in girls it was 0.4 and 1.4% respectively (2). In a report on the nationwide Health Behaviour in School Children Survey (HBSC) 2000/2001 of the World Health Organization (WHO), Finland had a prevalence of overweight and obesity comparable to the HBSC average, but a higher prevalence compared to other Scandinavian countries (3). Cut-off points for body mass index (BMI) are internationally agreed upon (1,4), and form the basis for the estimation of the prevalence of overweight and obesity among adolescents. The cut-off values for overweight and obesity among adults are BMI 25 kg/m 2 and BMI 30 kg/m 2 respectively (1). In adolescents, BMI (and therefore the cut-off values for overweight and obesity) increase with chronological age and vary according to gender, body composition and the Abbreviations BMI, body mass index; HBSC, health behaviour in school-age children; IOTF, International Obesity Task Force; WC, waist circumference; WHO, World Health Organization. stage of pubertal maturation (1,5,6). The WHO has provided international reference values for BMI adjusted to age and pubertal maturation. Adolescents with a BMI 85th percentile should be considered as being at risk for overweight (1). The International Obesity Task Force (IOTF) recommends another international classification system for childhood and adolescent obesity (4). Healthcare professionals and researchers, though not many individuals, use these reference data. For individuals, the stage of pubertal maturation is difficult to determine and the value of BMI hard to interpret, as BMI is an indirect measure of weight and height. Another complicating factor is that body weight is highly dependent on body composition (7). Recently, with an understanding of the importance of body fat distribution, abdominal obesity in particular has become a matter of concern as a risk factor for many diseases (6,8). Several studies, in both adults and adolescents, show that body composition is a better predictor of obesityrelated metabolic complications than body weight (8 12). Waist circumference (WC) is a highly sensitive and specific measure of abdominal body fat in children and adolescents at different ages (13). Trends in increasing WC over the past years have exceeded those in BMI, particularly in girls, showing that BMI is a poor proxy for central fatness (14). WC as a measure has been recommended for health professionals working with weight management in adults (15). C 2008 The Author(s)/Journal Compilation C 2008 Foundation Acta Pædiatrica/Acta Pædiatrica , pp

2 In adolescent girls, body perception rather than BMI has been shown to be important for individuals health and weight control behaviour, but is rarely used in prevention programmes (16,17). In creating prevention programmes, international cut-off points for BMI and to a lesser extent WC are used (1,4,15). BMI is found to correlate poorly with body perception (18). This discrepancy between professional classification and individual evaluation of body size can cause difficulties in creating effective prevention and treatment programmes for weight-related health problems in young people. The objective of this study was therefore to examine whether WC, as the most recent indicator of weight-related health problems used by health professionals for adults, is related to adolescent girls body perception and maternal perception of their daughter s body size. SUBJECTS AND METHODS Subjects The study population consisted of all 5th to 12th grade girls, present at all existing schools in Sodankylä, a small town in the rural arctic region of Finland and their parents. Before the start of the fieldwork, both the parents and girls consent was requested by letter. The local health centre and the involved schools complied with the study plans. Once a year, over three consecutive years, all girls in the 5th to 12th grades were invited to participate by completing a questionnaire followed by anthropometric measurements during a visit by the research team to the schools. Only girls were included as this study is a part of a larger study concerning dietary behaviour in girls, which is disturbed more frequently in the female population. Families received an invitation letter with a questionnaire to be completed by one of the parents at home. Pooled data, consisting of 296 parents (69%) and 370 girls (88%) who participated in at least one of the three measurement periods were analysed. Of the girls and parents participating more than once, only data from the first time they participated in the study were included. To study possible bias in the pooled data because of awareness the second and third year of the study, pooled data were compared to data from the first year of the study (n = 213). To be able to evaluate the characteristics of the dropouts, we compared data from girls participating only once (n = 199) with girls participating all three years (n = 72). Furthermore we compared the group completing both the body measurements and the questionnaire (n = 286) with those not participating in body measurements (n = 50). Of the adults answering the questionnaire, 95% were mothers (n = 281), 5% fathers (n = 14) and 0.3% stepmothers (n = 1) of the girls aged years. The number of participating fathers was too small for separate analyses of the answers as well as including them in the whole group since we cannot assume paternal answers being equivalent to maternal answers. Therefore fathers were excluded from further analyses. Questionnaires In developing the questionnaires, we used relevant items from the international WHO study on Health Behaviour in School-age Children (HBSC) (19). To assess the girls body perception, we asked for their own estimation of their height in metres and weight in kilograms, immediately followed by an item on their body perception, Do you think your body is.... Answer categories on a five-point Likert scale ranged from far too thin to far too fat (19). This item concerning body dissatisfaction was similar but not identical to variables of proven validity in the literature on body perception disturbances (20). Maternal participation consisted of completing a questionnaire at home. The mother completed the same item on the girls body perception as mentioned above. In case more than one daughter in a family participated, the item was completed for each daughter separately. Mothers returned their questionnaires in enclosed prepaid envelopes. Anthropometric measurements Measurements were performed at school during school hours. The height (cm) and weight (kg) of the girls were measured using school equipment after students had completed the questionnaire. WC (cm) was measured midway between the tenth rib and the iliac crest (21). In addition to the physical measurements obtained directly, we also calculated BMI (BMI = weight (kg)/height 2 (cm 2 )). Classification systems for anthropometric measurements For BMI, cut-off points for each age were set as >95th, 85th to 95th, 15th to 85th, 5th to 15th and <5th percentiles according to international reference values available from the WHO and covering all weight categories from severe underweight to obesity (1). In addition, we used the cut-off points for BMI defined by Cole et al., covering childhood overweight and obesity only. For WC, international cut-off points have not yet been defined. The study population used by McCarthy et al. for British cut-off points was chosen here as it was considered the most comparable to our study population. The cut-off points for each age were set as >95th, 90th to 95th, 10th to 90th, 5th to 10th and <5th percentiles (21). Statistical methods The information collected was coded and entered into the statistics program Statistica 7.0 (StatSoft, Inc., Tulsa, OK, USA). We used linear regression to compare measured and self-reported height and weight. To study the effect of age on the anthropometry of the girls, linear regression modelling was performed. To adjust for age effects during growth, partial correlation coefficients were calculated. The sign test was used to compare the girls and mothers body perception with classification according international reference values for BMI and WC. For comparison of the girls body perception with maternal body perception, sign tests were also used. The level of significance for all analyses was set at p < C 2008 The Author(s)/Journal Compilation C 2008 Foundation Acta Pædiatrica/Acta Pædiatrica , pp

3 Table 1 Mean and standard deviations for weight, height, BMI and waist circumference of girls aged years (mean ± SD) Age (years) n Weight (kg) Height (cm) BMI (kg/m 2 ) Waist (cm) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 6.5 Table 2 Comparison of the girls body perception on a five-point scale with measured BMI classified according to WHO cut-off points (n = 294). The marked cells show the number of girls overestimating their body size compared to measure BMI (n = 107). Body perception significantly overestimated actual body size for all weight categories (p < ) RESULTS Physical measurements Table 1 shows the physical characteristics of the girls by age. All anthropometric measures increased with age (p < 0.001). Partial correlation analyses showed a correlation coefficient of 0.88 between weight and WC and a coefficient of 0.91 between WC and BMI (p < for both). Classifying the girls in weight categories using the international reference values for BMI defined by the WHO put the girls in a lower weight category than using the international reference values for WC (p < ). The analyses of the dropouts did not show significant differences in anthropometric measures between girls participating once (n = 199) compared to girls participating three times in the anthropometric measurements (n = 72). Measured height and weight compared to self-reported height and weight There was no significant difference between the girls measured height and self-reported height in centimetres. Regression modelling on measured and self-reported weight in kilograms showed a slight but significant overestimation at lower weights and underestimation at higher weights (p < 0.05). Underweight individuals overestimated their weight by 0.43 kg (n = 29), normal weight individuals underestimated their weight by 0.41 kg (n = 247) and overweight individuals underestimated their weight by 0.84 kg (n = 14). The mean deviation of self-reported weight from measured weight was 0.34 kg (n = 290). Corresponding analysis on data of the first year of the study only showed an overestimation of 0.32 kg for underweight individuals (n = 22), an underestimation of 0.47 kg for normal weight individuals (n = 181) and an underestimation of 1.13 kg for overweight individuals (n = 10). The mean deviation of self-reported weight from measured weight was 0.37 kg during the first year of the study (n = 213). Body perception in relation to anthropometric measures The analyses of the drop outs showed that girls participating only once in the study perceived themselves more often overweight or obese than the girls participating all three years of the study (p < 0.05). Forty percent of the girls completingthequestionnaireonly (n = 47) perceived themselves overweight or obese compared to 33% of the girls participating in both measurements and questionnaire (n = 280). Table 2 compares the girls body perception with the WHO classification of measured BMI. The girls perceived themselves consequently larger than the classification based on their measured BMI (p < ). Performing the same procedure on the classification for WC according to McCarthy s reference values, there was no significant overor underestimation of body size by the girls themselves. Using the reference values for BMI and WC mentioned above, 37% and 20% of the girls respectively (n = 294 and n = 271 respectively) believed themselves to be larger than measured. Agreement of body perception, reported by the girls on a five-point scale, with the WHO classification and the WC classification, independent of whether the girl was categorized as underweight, normal weight or overweight, did not show a significant difference between classification according BMI and classification according WC. Figure 1 shows the percentage of girls that perceived themselves as overweight despite classification as nonoverweight on the basis of BMI defined by the WHO and Cole et al. (n = 294) respectively, and for WC (n = 271). The girls perceived themselves less often overweight when categorized as non-overweight according to WC than according to BMI (p < ). There was no significant difference in girls perceiving themselves overweight using BMI classification according to WHO as compared to BMI classification according to Cole et al. Body perception reported by adolescent girls and their mothers Maternal perception of their daughter s body size did not differ from the classification according to the international reference values for BMI defined by the WHO. Mothers classified their daughters as smaller than the classification according to the international reference values for C 2008 The Author(s)/Journal Compilation C 2008 Foundation Acta Pædiatrica/Acta Pædiatrica , pp

4 mal weight or overweight, classified themselves in a higher weight category than their mothers both in relation to BMI defined by the WHO and to WC (p < ). Comparison of the agreement of the girls body perception and their mothers perception with BMI showed that maternal perceptions agreed more often than those of the girls with the international WHO reference value for BMI (p < 0.001). The girls and their mothers body perception agreed similarly when related to WC. As shown in Figure 1, when related to each of the reference values for BMI and WC, the girls regarded themselves significantly more often than their mothers as overweight despite being measured non-overweight. Figure 1 The percentage of girls perceived as overweight or obese when not classified as such is represented by black bars according to the WHO BMI, by grey bars according to Cole et al. s BMI, and by striped bars according to waist circumference. The percentage of girls perceived as overweight or obese by girls (n = 101) and by mothers (n = 18) are presented separately and compared. p < WC (p < ). Independent of whether the girl was categorized as underweight, normal weight or overweight, the maternal perception agreed more often with BMI classified according to the WHO than with WC according to McCarthy (p < 0.001). Figure 1 shows the percentage of mothers that perceived their daughters as overweight despite classification as nonoverweight according to BMI defined by the WHO and Cole et al. (n = 18) or WC (n = 17). Mothers of non-overweight girls according to WC perceived their daughters less often overweight than mothers of non-overweight girls according to BMI (p < ). Of the mothers of overweight or obese girls according to WC, 98% perceived their daughters thinner than classified (n = 48) as shown in Figure 2. Of the girls classified as overweight or obese according to WC, 61% perceived themselves thinner than classified (n = 64), which is significantly less than their mothers (p < 0.001). The girls, independent of whether they were categorized as underweight, nor- Figure 2 Comparison of the girls (n = 64) and the maternal body perception (n = 48) of girls classified as overweight or obese according to WC. p < DISCUSSION This study reveals a discrepancy between the body perception of adolescent girls and the international classification of body size according to BMI used by health professionals worldwide. At the same time, considering their self-reports on height and weight, the girls showed an awareness of their body size and BMI. The measured and self-reported weights in our study showed an average difference of 0.34 kg. We found an underestimation of 0.40 kg in normal weight girls and 0.84 kg in overweight girls, compared to 0.52 kg in overweight adolescents found by Elgar et al. (22). The phenomenon of conscious underestimation in both normal weight and overweight girls indicates awareness of body weight. Analyses of data from the first year of the study showed a slightly larger difference between measured and self-reported weight as compared to the pooled results, assuming that the girls would be aware of the self-reports on body measures the second and third year of the study. If the girls were aware of their weights and the question of self report the second and third year, the self-reported body measures would be even more realistic and therefore strengthen the discrepancy between actual and perceived body size, which was the case. According to our study, the girls perception of their body size does not agree well with medical definitions of weight status based on BMI. Before interpretation, it is important to consider that the concept of body perception or body image is complex and multidimensional and therefore frequently found to be unrealistic when related to actual body size (16,17). However, the weak agreement with medical definitions could be simply due to the fact that BMI is a relative measure, a calculated index of height and weight, which can be difficult for adolescents to associate to. In addition, the cut-off points for BMI in adolescents are not as clear as in adults as they increase with age and vary with gender, the stage of pubertal maturation and body composition (1,5). Many girls tend to consider themselves fat even when not so according to BMI. When interpreting the BMI, both the fat and lean components of body mass must be considered (7). By not taking into account the natural increase in body fat during adolescence, the girl might regard herself bigger and fatter and classify her body size easily as too fat. Page and Fox also suggest that many female adolescents confuse the development of their mature female characteristics as 504 C 2008 The Author(s)/Journal Compilation C 2008 Foundation Acta Pædiatrica/Acta Pædiatrica , pp

5 becoming fatter (23). In this study, maternal perception did not show a comparable overestimation in relation to BMI, perhaps because of taking into account growth and development during puberty in their judgment. The timing of pubertal maturation in girls has also been shown to influence body perception: girls maturing early reported more often feeling too fat (24). In relation to WC, fewer girls showed body dissatisfaction in regarding themselves as fat when this was not the case. This finding suggests that the girls consider WC rather than BMI in their perception of their body, possibly due to the relation of WC to abdominal fat at different ages. Studies using body silhouettes to measure body perception are often related to BMI classification (25,26). A focus on other body parts than weight and height may reflect current physical ideals, as suggested by Bergström et al. They found that adolescents without anorexia nervosa overestimated their body size, particularly at the waist, their buttocks and thighs (27). It is not unlikely that WC, as a characteristic of body shape rather than body size, reflects the normal body shape that girls in Finland relate themselves to. The finding of a more realistic body perception when related to WC compared to BMI in girls could simply be due to different reference populations. The reference values for WC were obtained from a European population born around 1980 and therefore comparable to the actual study population born 1980 or later in Finland. The reference population used to define the reference values for the WHO was born one-decade earlier (1), implying risks for secular trends in overweight and obesity. Moreover, the WHO standard is based on data from the United Stated defined by the National Center for Health Statistics (NCHS) (1). The reference values defined by Cole et al. were more recent than WHO data, but were drawn from different nations worldwide and not from European countries only (4). In addition, the IOTF standard by Cole et al. define cut-off points for adolescent overweight and obesity only, whereas the WHO standard also covers the underweight categories. As shown in Figure 1, we compared body perception with body size classified according to WHO, IOTF and WC standard respectively for girls perceiving themselves as overweight. This does not suggest any implications of the choice of BMI standard for our results regarding body perception in girls classified as overweight or obese. However, WHO BMI and the WC standard use different percentiles as cut-off points. For example, the references supply cut-off points for overweight as the 85th percentile and 90th percentile for BMI and WC respectively (1,21). In our study, using the international reference values for BMI put the girls in a lower weight category than using the international reference values for WC, implying a greater risk for overestimation of body size with BMI than WC. However, mothers did not overestimate the body size of their daughters in relation to BMI; but they underestimated their body size in relation to WC. The perceptions of body size reported by the girls and their mothers did not agree very well. The girls themselves had a more negative body image and felt fatter than their mothers perceived them to be. At the same time, mothers perceived their daughters thinner than classified when the girls in fact were overweight, assuming either softening or denial of the overweight status of their daughter. In the US study by Goodman et al., parents were found to be more accurate in their perception than teens. As overweight and obesity are subjective emotional experiences of one s body, a better understanding of this dimension by healthcare professionals and individuals is an important complement to physical measurements in order to assess, diagnose, and treat the condition (18). The drop out rate in the present study showed a trend of non-participation related to the perception of overweight, confirming the importance of subjective emotional experience. The girls own body perception rather than that of their parents might therefore be important in prevention and intervention programmes, as the development of adult lifestyle and behaviour occurs during adolescence. To create effective prevention and intervention programmes for overweight and obesity in adolescents, we suggest measuring WC in schools and health care in order to diminish the discrepancy between measured and perceived body size. In adults, WC is the most recent indicator of weight-related health problems used by health professionals (15), while body perception has been found to be an important target of intervention to improve subjective health in adolescence (28). WC in adolescents, used by both health professionals and individuals, could serve as an additional objective measure and a common target for intervention in adolescent girls. This implies guidelines and cut-off points adjusted for age for WC in adolescents to determine abdominal overweight and related health risks at an early stage. This should be a help rather than a threat for adolescent girls in creating and keeping a healthy body perception. International guidelines regarding WC in adolescent girls are not yet available (21,29). In establishing such guidelines, there is a risk for the development of unhealthy weight control practices in adolescent girls. By using guidelines for WC rather than BMI, the risk of dysfunctional health behaviour would, we believe, be less likely: the weight control practices used will have the effect the girls are aiming for, namely diminishing WC. Body weight and BMI, however, increase when fat mass is replaced by heavier fat-free mass. For a better understanding of the role of WC in the critical teenage years, further research is necessary on WC, overweight and body perception in adolescents, including such factors as dieting behaviour and pubertal development. ACKNOWLEDGEMENTS The authors would like to thank Maria Jokinen, Suvi Ahonen and Satu Forsman for their assistance in data collection. We would also like to thank all the staff in the enrolled schools in Sodankylä for their time and support during the data collection periods. We further wish to thank Olle Eriksson for his assistance and support in the statistical analysis. We wish to express our gratitude to the Juho Vainio Foundation, the Finnish Cultural Foundation and the Erik Johan Ljungberg Educational Fund for their financial support of the study. C 2008 The Author(s)/Journal Compilation C 2008 Foundation Acta Pædiatrica/Acta Pædiatrica , pp

6 References 1. WHO Expert Committee on Physical status: The use and interpretation of anthropometry. WHO technical report series; 854, Geneva, Kautiainen S, Rimpela A, Vikat A, Virtanen SM. Secular trends in overweight and obesity among Finnish adolescents in Int J Obes Relat Metab Disord 2002; 26: Mulvihill C, Németh Á, Vereecken C. Body image, weight control and body weight. In: Currie C, et al. editors. Young People s Health in Context: international report from the HBSC 2001/02 survey. WHO Policy Series: Health policy for children and adolescents Issue 4, Copenhagen: WHO Regional Office for Europe, 2004: Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 2000; 320: Bini V, Celi F, Berioli MG, Bacosi ML, Stella P, Giglio P, et al. Body mass index in children and adolescents according to age and pubertal stage. EurJClinNutr2000; 54: Lahti-Koski M, Pietinen P, Männistö S, Vartiainen E. Trends in waist-to-hip ratio and its determinants in adults in Finland from 1987 to Am J Clin Nutr 2000; 72: Maynard LM, Wisemandle W, Roche AF, Chumlea C, Guo SS, Siervogel RM. Childhood body composition in relation to body mass index. Paediatrics 2001; 107: Pouliot MC, Despress JP, Lemieux S, Moorjani S, Bouchard C, Tremblay A, et al. Waist circumference and abdominal sagittal diameter: best simple anthropometric indexes of abdominal visceral adipose tissue accumulation and related cardiovascular risk in men and women. Am J Cardiol 1994; 73: Rankkinen T, Kim SY, Perusse L, Despres JP, Bouchard C. The prediction of abdominal visceral fat level from body composition and anthropometry: ROC analysis. Int J Obes Relat Metab Disord 1999; 23: Freedman D, Serdula MK, Srinivasan SR, Berenson GS. Relation of circumferences and skinfold thicknesses to lipid and insulin concentrations in children and adolescents: the Bogalusa Heart Study. Am J Clin Nutr 1999; 69: Flodmark CE Sveger T, Nilsson-Ehle P. Waist measurement correlates to a potentially atherogenic lipoprotein profile in obese year old children. Acta Paediatr 1994; 83: Savva SC, Tornaritis M, Savva ME, Kourides Y, Panagi A, Silikiotou N, et al. Waist circumference and waist-to-height ratio are better predictors of cardiovascular disease risk factors in children than body mass index. Int J Obes Relat Metab Disord 2000; 24: Daniels SR, Khourty PR, Morrison JA. Utility of different measures of body fat distribution in children and adolescents. Am J Epidemiol 2000; 152: McCarthy HD, Ellis SM, Cole TJ. Central overweight and obesity in British youth aged years: cross-sectional surveys of waist circumference. BMJ 2003; 326: Han TS, van Leer EM, Seidell JC, Lean ME. Waist circumference as a screening tool for cardiovascular risk factors: evaluation of receiver operating characteristics (ROC). Obes Res 1996; 4: Strauss RS. Self-reported weight status and dieting in a cross-sectional sample of young adolescents: National Health and Nutrition Examination Survey III. Arch Pediatr Adolesc Med 1999; 153: Mikkilä V, Lahti-Koski M, Pietinen P, Virtanen SM, Rimpelä M. Associates of obesity and weight dissatisfaction among Finnish adolescents. Public Health Nutr 2003; 6: Goodman E, Hinden BR, Khandelwal S. Accuracy of teen and parental reports of obesity and body mass index. Pediatrics 2000; 106: Wold B, Aarø LE, Smith C. Health behaviour in school-age children. A WHO cross-national survey. Research protocol for the survey. HEMIL-rapport, 4, Research center for Health Promotion, University of Bergen, Stewart TM, Williamson DA. Assessment of body perception disturbances. In: Thompson K (ed). Handbook of eating disorders and obesity. Hoboken, NJ: John Wiley and sons, 2004, McCarthy HD, Jarrett KV, Crawley HF. The development of waist circumference percentiles in British children aged y. Eur J Clin Nutr 2001; 55: Elgar FJ, Roberts C, Tudor-Smith C, Moore L. Validity of self-reported height and weight and predictors of bias in adolescents. J Adolesc Health 2005; 37: Page A, Fox KR. Is body composition important in young people s weight management decision-making? Int J Obes 1998; 22: Williams JM, Currie CE. Self-esteem and physical development in early adolescence: pubertal timing and body perception. J Early Adolesc 2000; 20: Peterson M, Ellenberg D, Crossan S. Body-image perceptions: reliability of a BMI-based Silhouette Matching test. Am J Health Behav 2003; 27: Lazzeri G, Casorelli A, Giallombardo D, Grasso A, Guidoni C, Menoni E, et al. Nutritional surveillance in Tuscany: maternal perception of nutritional status of 8.9 year old school-children. JPrevMedHyg2006; 47: Bergström E, Stenlund H, Svedjehäll BI. Assessment of body perception among Swedish adolescents and young adults. J Adolesc Health 2000; 26: Meland E, Haugland S, Breidablik H-J. Body perception and perceived health in adolescence. Health Educ Res 2007; 22: Vissers D, Vanroy C, De Meulenaere A, Van de Sompel A, Truijen S, Van Gaal L. Metabolic syndrome in youth: a cross-sectional school-based survey. Acta Paediatr 2007; 96: C 2008 The Author(s)/Journal Compilation C 2008 Foundation Acta Pædiatrica/Acta Pædiatrica , pp