PEDIATRICOBESITY ORIGINALRESEARCH

Body-weight perception and related preoccupations in a large national sample of adolescents V. Deschamps1,2, B. Salanave1,2, C. Chan-Chee3, M. Vernay1,2 and K. Castetbon1,2 1

Unité de Surveillance et d’Epidémiologie nutritionnelle (Usen), Institut de Veille sanitaire (InVS), Saint-Maurice, France; 2Unité de Surveillance et d’Epidémiologie nutritionnelle (Usen), Université de Paris 13, Bobigny, France; 3Département des Maladies chroniques et traumatiques, Institut de Veille sanitaire (InVS), Saint-Maurice, France Received 12 April 2013; revised 24 September 2013; accepted 28 October 2013

Summary Objectives: This study aimed to investigate the association between body-weight (BW) perception, weight preoccupation and behaviour, including weight control practices and compulsive over-eating episodes, across gender and actual BW classes. Design: This study used a cross-sectional observational study. Participants: A large, nationally representative sample of 6404 ninth-grade French adolescents was randomly selected from schools throughout France.

Methods: Weight and height were measured, and BW preoccupation, BW control practices and compulsive over-eating were self-reported using standardized questionnaires. Results: Nearly one-third of adolescents misperceived their BW. Misperception was more frequent among girls than boys (42.2% vs. 27.3%, P < 0.01). Underestimation of BW among overweight adolescents, like BW overestimation among underweight adolescents, was associated with less preoccupation with weight and fewer weight control practices than accurate perception of BW. Normal weight adolescents who overestimated their BW were more likely to declare weight preoccupations (ORa = 8.66 [6.67–11.25]), dieting (ORa = 4.81 [3.68–6.27]) and recurrent compulsive over-eating episodes (ORa = 2.36 [1.72–3.23]) compared with their counterparts who correctly estimated their BW. Conclusion: Our study underlines the role of these associations in each category of actual BW (underweight, normal weight and overweight) in a large national sample. Keywords: Adolescent, behaviour, BMI, perception. Abbreviations: AN, anorexia nervosa; BMI, body mass index; BW, body weight; CI, confidence interval; EAT, Eating Among Teens; EPZ, Educational Priority Zones; GUTS, Growing Up Today Study; INCA, Individuelle nationale des Consommations alimentaires; IOTF, International Obesity Task Force; OR, odds ratio; YRBS, Youth Risk Behavior Survey

Introduction Misperception of weight status is defined as discordance between an individual’s actual body weight (BW) and his or her perception of weight status. Recent studies have highlighted associations between adolescent BW misperception and weight control practices (1,2) and eating disorders (3). Like misperception, weight concerns among adolescents have also been reported to be associated with these behaviours (4,5). Weight preoccupations and weight control practices are not inherently favourable or deleterious to health, but depend on weight status. For instance, it

is appropriate to gain weight when underweight, to lose weight when overweight or obese and to maintain weight when within a normal weight status. The desire to lose weight when under- or normal weight status is associated with increased disordered eating, whereas the desire to gain weight when of normal or overweight status may lead to negative health consequences of further weight gain or loss, respectively (6). Weight status category should therefore be taken into account to explore the association between misperception, weight preoccupation and behaviour, including weight control practices and disordered eating behaviours. Indeed, weight control practices

Address for correspondence: Dr V Deschamps, Unité de Surveillance et d’Epidémiologie Nutritionnelle (Usen), Institut de Veille Sanitaire (InVS)/Université de Paris 13, 74 rue Marcel Cachin, 93017 Bobigny Cedex, France. E-mail: [email protected] © 2014 The Authors Pediatric Obesity © 2014 International Association for the Study of Obesity. Pediatric Obesity 10, 15–22

ORIGINALRESEARCH

doi:10.1111/j.2047-6310.2013.00211.x

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V. Deschamps et al.

such as dieting are found not only in overweight but also in underweight adolescents (7,8). Despite increasing attention directed towards the subject of weight perception in adolescents, only a few studies have concomitantly investigated a wide range of aspects of BW perception, associated weight preoccupations and weight control practices as related to actual BW status in a representative sample (9,10). The present analysis reports the prevalence of BW perception categories, weight preoccupations and weight control practices in a large representative sample of ninth-grade French adolescents. We also investigated the association between weight perception categories and preoccupation with weight, along with behaviour including weight control practices and compulsive over-eating, taking into account gender and actual BW class differences.

Materials and methods Population A total of 750 secondary schools participated in the study. The design has been described elsewhere (11). Briefly, a two-stage cluster sampling method was used to select participants. The first stage of sampling involved random selection of secondary schools, public and private, stratified on administrative school districts and the degree of urbanization, with oversampling among Educational Priority Zones (EPZ). EPZ schools are generally located in deprived areas and receive special support from the government. The second stage involved random selection of at least 10 adolescents from the ninth grade in each selected school. A letter was sent to the parents informing them about the survey and specifying that participation was on a voluntary basis; hence, they or their child were free to refuse. According to French regulations, examination of the study protocol by the National Ethics Committee was not required, as the triennial cycle of surveys in schools was implemented by the Ministries of Health and Education as part of a national health programme.

Measurements Social and demographic information (including age, gender, birth rank, family structure, parental occupational category and school situation as related to the EPZ) was collected through the face-to-face questionnaire. A self-administered questionnaire (included questions about self-perceived BW, weight preoccupations, weight control practices and compulsive over-eating episodes) was filled out by the adolescent several days before the medical examination. The examination,

including anthropometric measurements, was carried out by nurses or physicians from the French Ministry of Education using standardized procedures. Weight and height were measured using a standardized protocol. Body mass index (BMI) was calculated. The International Obesity Task Force sex- and age-adjusted cut-off values, based on percentiles passing through BMI 25 and 30 kg m−2 at age 18, were used to define overweight and obesity, respectively (12), whereas cut-off values based on percentiles passing through BMI 17.0 and 18.5 kg m−2 in 18-year-old adolescents were used to define thinness grades II and I (13), respectively. Perceived weight was assessed using a single question ‘How do you view yourself?’ with five response options as follows: ‘I’m very thin’, ‘I’m quite thin’, ‘I’m fine’, ‘I’m quite fat’ and ‘I’m very fat’. Misperception of weight status was defined as the discordance between the subjects’ perceived and measured (actual) weight categories. Participants were grouped into one of the following three cases: (i) ‘no misperception’: self-perceived weight was concordant with the measured category; (ii) ‘underestimation’: self-perceived weight was in a lighter weight category than that measured and (iii) ‘overestimation’: self-perceived weight was in a heavier weight category than that measured. Weight preoccupations, weight control practices and occurrence of compulsive over-eating episodes were investigated using questions presented in Table 1. To minimize participant burden and increase the accuracy of collected data, we used items with simple response options such as yes/no as opposed to multi-item scales. Weight preoccupations were assessed by two questions (regarding fear of weight gain and preoccupation with weight) derived from the Drive for Thinness Subscale of the Eating Disorder Inventory-3 (14). Item about wanting to change BW was specifically constructed for this study. The three questions concerning weight control practices were derived from the ‘Eating Among Teens and Young Adults’ study (15). Recurrent occurrence of compulsive over-eating episodes was explored using a question which took into account Diagnostic and Statistical Manual of Mental Disorders, Fourth edition and International Statistical Classification of Diseases and Related Health Problems criteria to define recurrence (at least twice a week for 3 months) of eating disorders. Adolescents were considered to have bulimia symptoms if they had recurrent compulsive over-eating episodes, and body shape/weight preoccupations and inappropriate compensatory behaviour.

© 2014 The Authors Pediatric Obesity © 2014 International Association for the Study of Obesity. Pediatric Obesity 10, 15–22

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Table 1 Questions about weight preoccupations, weight control practices and compulsive over-eating episodes

Weight preoccupations Wants to change BW Afraid of putting on weight Preoccupied by BW

Questions

Response options*

Do you wish to change your body weight? Are you afraid to put on weight?

‘No’ or ‘yes’ ‘Never’, ‘rarely’, ‘often’, ‘very often’ ‘Never’, ‘rarely’, ‘often’, ‘very often’

Are you preoccupied with your body weight?

Weight control practices Struggles to maintain or return Do you have to struggle to maintain or return to ‘Never’, ‘rarely’, ‘often’, to desired weight your desired weight? ‘very often’ Weighs oneself How often do you weigh yourself? ‘Never’, ‘once a month’, ‘less than once a week’, ‘once a week’, ‘2–6 a week’, ‘once a day or more’ Goes on a diet Do you often go on a diet? ‘Never’, ‘sometimes’, ‘regularly’ Compulsive over-eating episodes Recurrent compulsive I had compulsive over-eating at least twice ‘No’ or ‘yes’ over-eating weekly for 3 months. Bulimia symptoms I had recurrent compulsive over-eating episodes ‘No’ or ‘yes’ with body shape/weight preoccupations and the onset of inappropriate compensatory behaviour to prevent weight gain, such as self-induced vomiting, use of laxatives, diuretics, fasting or excessive exercise. *In bold, response options reported by adolescents who were considered preoccupied with their body weight (BW), declared weight control practices or compulsive over-eating episodes.

Statistics Analyses were performed in adolescents for whom we had complete information on age, gender, anthropometric measurements, weight perception, weight preoccupations, weight control practices and compulsive over-eating. Differences in categorical data were tested using a chi-square test. Logistic regression was used to investigate the association between misperception of weight and weight preoccupations, weight control practices and compulsive over-eating episodes. A separate model for each of the three outcome variables was developed. The reference group consisted of subjects who reported ‘no weight preoccupations’, ‘no weight control practices’ and ‘no compulsive overeating episodes’, respectively. For compulsive overeating episodes, bulimia symptoms were not introduced into these analyses because of their infrequent occurrence, particularly among boys. Analyses were stratified by gender and adjusted for socioeconomic factors (residing in an EPZ, parental occupational category, etc.) and family environmental factors (family structure, birth rank, etc.). Indeed, the role of interpersonal relationships with family

members, and particularly the role of siblings in the development of body image and eating disturbances, has been shown in previous studies (16). To explore the relationship between BW misperception and its related preoccupations, weight control practices and compulsive over-eating episodes while taking into account the actual BW status, logistic regressions were stratified by actual BW categories and controlled for the same covariates. In these analyses, both girls and boys were included in the models to increase the number of subjects in each category, and analyses were adjusted for gender. Adolescents classified into thinness grades I and II were considered underweight, whereas adolescents classified as overweight or obese were considered overweight. All analyses were performed using the STATA® V.10 (Stata Corporation, College Station, TX, USA) statistical software program, and took complex sampling into account. The declaration function for complex sampling design (‘svyset’ and ‘svy:’ options) was used. Calibration was used to provide nationally representative results. The complex survey design and weighting were accounted for in all analyses.

© 2014 The Authors Pediatric Obesity © 2014 International Association for the Study of Obesity. Pediatric Obesity 10, 15–22

ORIGINALRESEARCH

Weight perception in French adolescents

V. Deschamps et al.

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Figure 1 Concordance between actual body-weight status and self-perceived body weight by actual body-weight status and gender in ninth-grade adolescents in France (2003–2004).

Results The characteristics of the 7,538 adolescents randomly selected were compared with national characteristics of adolescents from the ninth grade (gender, age, EPZ, degree of urbanization, administrative school district and private or public school). Before calibration and because of the sampling design, the proportion of 14-year-old adolescents was lower in the sample than in the population. Schooling in an EPZ was oversampled, and private schools were less frequently represented in the sample. However, calibration was carried out on these variables in order to correct participation bias. Among the 7,538 adolescents selected, 631 were excluded because of incomplete data pertaining to actual BW and/or sociodemographic characteristics, another 217 because of missing total selfadministrated questionnaires and 286 because of incomplete data on BW perception, weight preoccupations or weight control practices, even though they had completed the self-administered questionnaire. Consequently, 6,404 persons (85%) were included in the present analyses. There were no statistically significant differences in terms of sociodemographic status between included and excluded participants (data not shown). The general characteristics of the study population are presented in Supporting Information Table S1. Ages ranged from 12 to 18 years (mean = 14.5, standard deviation = 0.7) and girls accounted for 49.8% of the sample. Overall, 16.3% of the study population was overweight (including 3.9% who were obese), whereas 9.6% had a BMI lower than the ‘normal weight

range’ (Supporting Information Table S1). Boys were significantly more likely to consider their BW as ‘fine’ than girls. Girls considered themselves ‘quite fat’ or ‘very fat’ more often than boys (Supporting Information Table S1). Overall, two-thirds of the population (72.7% of boys vs. 57.8% of girls, P < 0.01) correctly evaluated their individual weight status (Fig. 1). Misperception was more frequent among girls than boys. Girls were significantly more likely than boys to overestimate their BW (33.9% vs. 9.0%, P < 0.001), whereas boys were more likely to underestimate it (18.3% vs. 9.3%, P < 0.001) (Fig. 1). Weight preoccupations, weight control practices and recurrent compulsive over-eating episodes were more frequent among girls than boys (Table 2). Preoccupation with BW and dieting was three times more common among girls than boys (Table 2). Misperception was significantly associated with weight preoccupations, weight control practices and recurrent compulsive over-eating episodes (Supporting Information Table S2). Adolescents from both genders who overestimated their weight status were more likely to declare weight preoccupations, weight control practices and recurrent compulsive over-eating episodes. Adolescents who underestimated their BW were less likely to worry about weight gain, to be preoccupied with BW or to diet regularly. There was no significant moderating impact of socioeconomic and family environment covariates on the relationship between weight perception and weight preoccupation, weight control practices and recurrent compulsive over-eating episodes.

© 2014 The Authors Pediatric Obesity © 2014 International Association for the Study of Obesity. Pediatric Obesity 10, 15–22

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Table 2 Percentage of ninth-grade adolescents in France (2003, 2004) reporting weight preoccupation, weight control practices or compulsive over-eating episodes Boys (n = 3153)

Girls (n = 3251)

%

%

(95% CI)

P*

(95% CI)

Weight preoccupations Wants to change BW (yes) 41.5 (39.2–43.8) 69.0 (66.8–71.1)

Body-weight perception and related preoccupations in a large national sample of adolescents.

This study aimed to investigate the association between body-weight (BW) perception, weight preoccupation and behaviour, including weight control prac...
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