a1 Department of Molecular and Developmental Medicine, Research Centre for Health Promotion and Education, University of Siena, Via A. Moro, 53100 Siena, Italy
a2 Health Promotion Research Centre, National University of Ireland Galway, Galway, Republic of Ireland
a3 Department of Public Health, Ghent University, Ghent, Belgium
a4 Center for Research in Human Nutrition, INSERM 557, University of Paris13, Paris, France
Objective To describe the prevalence of ‘graded thinness’ in children aged 11, 13 and 15 years in eleven developed countries and to identify trends in the prevalence of ‘thinness’ (BMI < 17 kg/m2 at age 18 years) by age and gender.
Design Cross-sectional study using data collected through self-reported questionnaires.
Setting Data were taken from the 1997/1998, 2001/2002 and 2005/2006 surveys of the Health Behaviours in School-aged Children (HBSC) Study.
Subjects Children and adolescents from ten European countries and the USA (n 158 000).
Results Prevalence of grades 1, 2 and 3 of thinness was higher among 11-year-old students compared with the 13- and 15-year-olds in all countries. A higher prevalence of thinness was observed in girls than in boys. Since 1998 the prevalence of thinness decreased steadily in Czech boys and girls, while it increased for French girls. In the total European sample of females, thinness decreased from 1998 to 2006 (χ 2 for trend, P < 0·01). Age-adjusted logistic regression analysis showed that Czech boys and girls, and Flemish and American girls were less likely to be thin in 2006 than in 1998; while a noteworthy increment, even if borderline significant, was observed for French girls with a 41 % increase in the likelihood to be thin.
Conclusions Our findings suggest that thinness is an important overlooked phenomenon with wide variation in prevalence and trends across developed countries. It deserves further longitudinal studies in a multinational context that could increase the understanding of the factors associated with thinness and contribute to developing preventive and nutritional programmes targeted at controlling obesity and chronic diseases, while monitoring thinness.
(Received November 26 2012)
(Revised June 11 2013)
(Accepted August 18 2013)
(Online publication September 24 2013)