From their school health files, the body mass index of 2607 children, 1268 boys and 1339 girls, from the Brussels region of Belgium was analysed. The aim was to study the relationship between obesity and social class, gender and nationality. In Belgian girls, the lower their social class, the higher was the prevalence and severity of obesity. There was no such significant relationship in Belgian boys, nor in immigrant children of either sex, although the overall prevalence of obesity was similar in all groups. These results question certain hypotheses proposed to explain the relationship between social class and obesity.
Conclusion: From early adolescence on, social inequality influences the prevalence of obesity in Belgian girls, but not in Belgian boys nor in immigrant children. Prevention of obesity should take into account the influence of gender, social class and ethnic origin.