Background: The European IDEFICS (Identification and prevention of dietary-and lifestyle-induced health effects in children and infants) study was set up to determine the aetiology of overweight, obesity and related disorders in children, and to develop and evaluate a tailored primary prevention programme. Objective: This paper focuses on the aetiological element of the multicentre study, the measures and examinations, sociodemographic characteristics of the study sample and proportions of participation. Design: Prospective cohort study with an embedded intervention study that started with a baseline survey in eight countries in [2007][2008]. Subjects and measurements: Baseline participants of the prospective cohort study were 16 224 children aged 2-9 years. Parents reported sociodemographic, behavioural, medical, nutritional and other lifestyle data for their children and families. Examinations of children included anthropometry, blood pressure, fitness, accelerometry, DNA from saliva and physiological markers in blood and urine. The built environment, sensory taste perception and other mechanisms of children's food choices and consumer behaviour were studied in subgroups. Results: Between 1507 and 2567, children with a mean age of 6.0 years and an even sex distribution were recruited from each country. Of them, 82% lived in two-parent families. The distribution of standardised income levels differed by study sample, with low-income groups being strongly represented in Cyprus, Italy and Germany. At least one 24-h dietary recall was obtained for two-thirds of the children. Blood pressure and anthropometry were assessed in more than 90%. A 3-day accelerometry was performed in 46%, motor fitness was assessed in 41%, cardiorespiratory fitness in 35% and B11% participated in taste perception tests. The proportion of children donating venous blood, urine and saliva was 57, 86 and 88%, respectively. Conclusion: The IDEFICS cohort provides valuable data to investigate the interplay of social, environmental, genetic, physiological and behavioural factors in the development of major diet-and lifestyle-related disorders affecting children at present.

Objective: To investigate the reproducibility of food consumption frequencies derived from the food frequency section of the Children's Eating Habits Questionnaire (CEHQ-FFQ) that was developed and used in the IDEFICS (Identification and prevention of dietary-and lifestyle-induced health effects in children and infants) project to assess food habits in 2-to 9-year-old European children. Design and methods: From a subsample of 258 children who participated in the IDEFICS baseline examination, parental questionnaires of the CEHQ were collected twice to assess reproducibility of questionnaire results from 0 to 354 days after the first examination. Weighted Cohen's kappa coefficients (k) and Spearman's correlation coefficients (r) were calculated to assess agreement between the first and second questionnaires for each food item of the CEHQ-FFQ. Stratification was performed for sex, age group, geographical region and length of period between the first and second administrations. Fisher's Z transformation was applied to test correlation coefficients for significant differences between strata. Results: For all food items analysed, weighted Cohen's kappa coefficients (k) and Spearman's correlation coefficients (r) were significant and positive (Po0.001). Reproducibility was lowest for diet soft drinks (k ¼ 0.23, r ¼ 0.32) and highest for sweetened milk (k ¼ 0.68, r ¼ 0.76). Correlation coefficients were comparable to those of previous studies on FFQ reproducibility in children and adults. Stratification did not reveal systematic differences in reproducibility by sex and age group. Spearman's correlation coefficients differed significantly between northern and southern European countries for 10 food items. In nine of them, the lower respective coefficient was still high enough to conclude acceptable reproducibility. As expected, longer time (4128 days) between the first and second administrations resulted in a generally lower, yet still acceptable, reproducibility. Conclusion: Results indicate that the CEHQ-FFQ gives reproducible estimates of the consumption frequency of 43 food items from 14 food groups in European children.

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Objective: To compare, specifically by age group, proxy-reported food group estimates obtained from the food frequency section of the Children's Eating Habits questionnaire (CEHQ-FFQ) against the estimates of two non-consecutive 24 h dietary recalls (24-HDR). Design: Estimates of food group intakes assessed via the forty-three-food-group CEHQ-FFQ were compared with those obtained by a computerized 24-HDR. Agreement on frequencies of intakes (equal to the number of portions per recall period) between the two instruments was examined using crude and de-attenuated Pearson's correlation coefficients, cross-classification analyses, weighted kappa statistics (k w ) and Bland-Altman analysis. Setting: Kindergartens/schools from eight European countries participating in the IDEFICS (Identification and prevention of Dietary-and lifestyle-induced health EFfects In Children and infantS) Study cross-sectional survey (2007)(2008). Subjects: Children aged 2-9 years (n 2508, 50?4 % boys). Results: The CEHQ-FFQ provided higher intake estimates for most of the food groups than the 24-HDR. De-attenuated Pearson correlation coefficients ranged from 0?01 (sweetened fruit) to 0?48 (sweetened milk) in children aged 2-,6 years (mean 5 0?25) and from 0?01 (milled cereal) to 0?44 (water) in children aged 6-9 years (mean 5 0?23). An average of 32 % and 31 % of food group intakes were assigned to the same quartile in younger and older children, respectively, and classification into extreme opposite quartiles was #12 % for all food groups in both age groups. Mean k w was 0?20 for 2-,6-year-olds and 0?17 for 6-9-year-olds. Conclusions: The strength of association estimates assessed by the CEHQ-FFQ and the 24-HDR varied by food group and by age group. Observed level of agreement and CEHQ-FFQ ability to rank children according to intakes of food groups were considered to be low.