Objective To examine the relation of dietary and physical activity (PA) patterns with the body mass index (BMI), and the associations between these patterns among children. Methods A representative sample of 21 111 school students aged 6-18 years was selected by multistage random cluster sampling from 23 provinces in the Islamic Republic of Iran. PA and dietary pattern were assessed by self-administered validated questionnaires. Findings Fruit and vegetables, dairy products and snacks (salty, fatty or sweet) had a similar consumption frequency of approximately twice a day. The type of fat most frequently consumed was hydrogenated solid fat (consumed by 73.8% of families). The PA level was significantly higher among boys than girls, in rural than in urban residents, and in intermediate students than high-school students. Among boys, the frequency of consumption of vegetables and plant proteins (R² = 0.46); and among girls, the frequency of consumption of dairy products and fruits, as well as high PA level had a significant inverse association with BMI (R² = 0.57). Among boys, the low frequency of consumption of fruits, the time spent on PA and the energy expenditure; and among girls, the time spent on PA and the energy expenditure, had significant relationships with overweight. When controlling for covariates, PA levels had significant relationships with the frequency of consumption of all food groups. Conclusion Unhealthy lifestyles make Iranian young people prone to chronic diseases later in life. When examining their health benefits, the interrelationship of dietary and PA behaviours should be considered. Voir page 24 le résumé en français. En la página 25 figura un resumen en español. IntroductionAccording to WHO estimates, by 2020, noncommunicable diseases (NCD) will account for approximately three quarters of all deaths in the developing world.1 Interest in childhood precursors to chronic diseases is increasing because the behavioural and biological risk fact t tors for chronic diseases persist from childhood into adulthood.2-4 Declining levels of physical activity (PA) as well as nutrition transition (i.e. the trend towards increased consumption of a diet high in saturated fat, sugar and refined foods, and low in fibre) among commut t nities are thought to be partly responsible for the rising rate of such risk factors worldwide. In this regard, a potential emerging public health concern in developing countries is likely to be the increasing incidence of childhood overweight, which in the future is likely to create an enormous public health burden. 8In recent years, in addition to problems in adults, the epidemiologit t cal transition has made Iranian young people prone to chronic diseases in later life. The project team obtained written informed consent from parents and oral assent from students. They selected school students by multistage random cluster sampling. Schools were stratified according to location (urban or rural), and the socioeconomic characteristics of their catchment area, taking into consi...

The findings of this study warrant the necessity of paying special attention to monitoring of the time trends in child obesity based on uniform definitions, as well as to design programmes to prevent and control associated factors.

Establishment of a uniform set of criteria for the MetS in children is needed. Routine WC measurement in the paediatric population may be clinically useful.

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