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The Relationship between Body Mass Index and Body Size Dissatisfaction in Young Adolescents: Spline Function Analysis

https://doi.org/10.1016/j.jada.2010.04.001Get rights and content

Abstract

This study assessed how body size dissatisfaction (BSD) varies in relationship to specific body mass index (BMI) values in a sample of preadolescents. A novel statistical approach based on spline function, suitable to assess in detail how two variables are related, was used. The study was conducted between December 2004 and March 2005. Students (aged 11 to 14 years) from seven selected secondary schools in Verona, Italy, were invited to participate. The final study group included 678 subjects. BSD was assessed using the Body Image Assessment Procedure. BMI values were expressed as z scores. It was found that, in the total sample, slightly underweight subjects (BMI z scores=−0.5) had no BSD. BSD progressively increased (current body size > ideal body size) for BMI z scores >−0.5 and became negative (ideal body size > current body size) for BMI z scores <−0.5. In boys, average weight subjects had no BSD. BSD progressively increased for BMI z scores >0 and became negative for BMI z scores <0. In girls, moderately underweight subjects (BMI z scores=−1) had no BSD. BSD progressively increased for BMI z scores >−1 and became negative for BMI z scores <−1. Although sex significantly moderated the relationship between BMI and BSD (P<0.001), socioeconomic status did not (P=0.459). Because average weight and slightly underweight young girls desired a thinner body, our study suggests that these subgroups should receive particular attention in public health programs as well as in dietetics clinical practice.

Section snippets

Design and Participants

During October 2004, seven junior high schools in Verona, Italy, were randomly selected and stratified to generate a socioeconomically diverse sample. All students (aged 11 to 14 years), except those with certified learning disabilities, were eligible for inclusion. The protocol was approved by the local ethics committee. Data collection was carried out between December 2004 and March 2005. Informed written consent was obtained from the parents of all participants and written assent was

Results and Discussion

A final sample of 678 subjects (79.9% of the registered students) was used for the statistical analysis.

The demographic and anthropometric characteristics of the subjects are reported in the Table. Interestingly, the BMI distribution of the subjects was very similar to that reported in the United States, according to national growth charts (23).

Most of the subjects (see the Table) presented with a BSD=0 (ie, CBS=IBS). Only about 16% of subjects presented with BSD values ≥4, although about 26%

Conclusions

This study provides insight into the inter-relationship between BMI and BSD in an Italian sample of young adolescents by means of a novel statistical approach, namely spline function analysis. Because the BMI values distribution and their correlation with CBS and IBS values were very similar to those reported in US samples of young adolescents, the results of this study might apply to the US population in the same age range, although a note of caution should be used because of the different

S. Cortese is a PhD at the Child Neuropsychiatry Unit, G. B. Rossi Hospital, Department of Mother-Child and Biology-Genetics, Verona University, Verona, Italy, and child psychiatrist, senior consultant in the Child and Adolescent Psychiatry Unit, University Hospital Clocheville, Tours, France

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    S. Cortese is a PhD at the Child Neuropsychiatry Unit, G. B. Rossi Hospital, Department of Mother-Child and Biology-Genetics, Verona University, Verona, Italy, and child psychiatrist, senior consultant in the Child and Adolescent Psychiatry Unit, University Hospital Clocheville, Tours, France

    B. Vincenzi is a resident in child neuropsychiatry, Child Neuropsychiatry Unit, G. B. Rossi Hospital, Department of Mother-Child and Biology-Genetics, Verona University, Verona, Italy

    M. Angriman is a resident in child neuropsychiatry, Child Neuropsychiatry Unit, G. B. Rossi Hospital, Department of Mother-Child and Biology-Genetics, Verona University, Verona, Italy

    B. Dalla Bernardina is a full professor, Child Neuropsychiatry Unit, G. B. Rossi Hospital, Department of Mother-Child and Biology-Genetics, Verona University, Verona, Italy

    S. Cook is a clinical psychologist in the Child and Adolescent Psychopathology Unit, Robert Debré Hospital, Paris VII University, Paris, France

    B. Falissard is a full professor at the INSERM U669; Paris-Sud University and Descarte University, Paris; Public Assistance–Paris Hospitals (AP-HP), Paris, France

    Y. Pigaiani is a clinical psychologist in the Child Neuropsychiatry and Psychology Unit, Local Socio-Health Unit 20, Verona, Italy

    C. Banzato is a resident in pediatrics, Department of Mother-Child, Biology and Genetics, Pediatric Section, Verona University, Verona, Italy

    G. Bogoni is a resident in pediatrics, Department of Mother-Child, Biology and Genetics, Pediatric Section, Verona University, Verona, Italy

    M. Pelligrino is a resident in pediatrics, Department of Mother-Child, Biology and Genetics, Pediatric Section, Verona University, Verona, Italy

    C. Maffeis is an associate professor, Department of Mother-Child, Biology and Genetics, Pediatric Section, Verona University, Verona, Italy

    D. Purper-Ouakil is a child psychiatrist, senior consultant in the Child and Adolescent Psychopathology Unit, Robert Debré Hospital, Paris VII University, Paris, France

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