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Background Living in single parent and blended families or as an only child-compared to living in two-parent biological families or with siblings, respectively-is associated with a higher body mass index (BMI) in cross-sectional studies. However, longitudinal research addressing the children's BMI in this context is scarce. Further, little is known about the association between family structure and metabolic health. Objectives This study aimed at investigating the association between both aspects of family structure with BMI and a metabolic score (MetS). Methods Cross-sectional data from 7804 children participating in the European multi-center I.Family study (2013/2014) and longitudinal data from 5621 children who also participated previously in the IDEFICS study (2007-2010) were used. Family structure was assessed by a detailed interview. BMI z-score and the MetS were based on measured anthropometry, blood pressure, high-density lipoprotein, blood glucose, and triglycerides. Linear regressions were performed to model associations between family structure with BMI and MetS. Results Children from single-parent families had higher BMI z-scores in the cross-sectional (beta = 0.09, 95% confidence interval [CI]: 0.001 to 0.18) and longitudinal analyses compared to those from two-parent families. Cross-sectionally, the number of siblings was associated with lower BMI z-scores (beta = -0.07, 95% CI: -0.10 to -0.03) and lower MetS (beta = -0.14, 95% CI: -0.26 to -0.01). Longitudinally, only children between baseline and follow-up had higher BMI z-scores at follow-up (beta = 0.07, 95% CI: 0.01 to 0.14) compared to stable siblings. Conclusion Obesity prevention measures should focus on single-parent households and families with an only child.

INTRODUCTION: Over the past decades, children have been increasingly using screen devices, while at the same time their sleep duration has decreased. Both behaviors have been associated with excess weight, and it is possible they act as mutually reinforcing behaviors for weight gain. The aim of the study was to explore independent, prospective associations of screen time and sleep duration with incident overweight in a sample of European children. METHODS: Data from 4,285 children of the IDEFICS/I.Family cohort who were followed up from 2009/2010 to 2013/2014 were analyzed. Hours per day of screen time and of sleep duration were reported by parents at baseline. Logistic regression analyses were carried out in separate and mutually adjusted models controlled for sex, age, European country region, parental level of education, and baseline BMI z-scores. RESULTS: Among normal weight children at baseline (N = 3,734), separate models suggest that every hour increase in screen time and every hour decrease in sleep duration were associated with higher odds of the child becoming overweight or obese at follow-up (OR = 1.16, 95% CI: 1.02-1.32 and OR = 1.23, 95% CI: 1.05-1.43, respectively). In the mutually adjusted model, both associations were attenuated slightly ( screen time OR = 1.13, 95% CI: 0.99-1.28; sleep duration OR = 1.20, 95% CI: 1.03-1.40), being consistently somewhat stronger for sleep duration. DISCUSSION/CONCLUSION: Both screen time and sleep duration increased the incidence of overweight or obesity by 13-20%. Interventions that include an emphasis on adequate sleep and minimal screen time are needed to establish their causal role in the prevention of overweight and obesity among European children. CC BY-NC 4.0https://www.karger.com/open-access/types-licences-copyright-costsPublished online: November 1, 2021Correspondence to: Monica Hunsberger, monica.hunsberger@gu.seFunding SourcesV.G.’s contribution to this study was supported by the Swedish Institute. The Swedish section of this study was co-financed by the Swedish Research Council for Environment, Agricultural Sciences, and Spatial Planning (2012-00038), the Swedish Research Council (2015-02508), the ALF-agreement for western Sweden (ALFGBG-722441), and the Swedish Research Council for Health, Working Life and Welfare (FORTE Grant 2014-01994).

Background: Many genes and molecular pathways are associated with obesity, but the mechanisms from genes to obesity are less well known. Eating behaviors represent a plausible pathway, but because the relationships of eating behaviors and obesity may be bi-directional, it remains challenging to resolve the underlying pathways. A longitudinal approach is needed to assess the contribution of genetic risk during the development of obesity in childhood. In this study we aim to examine the relationships between the polygenic risk score for body mass index (PRS-BMI), parental concern of overeating and obesity indices during childhood. Methods: The IDEFICS/I.Family study is a school-based multicenter pan-European cohort of children observed for 6 years (mean +/- SD follow-up 5.8 +/- 0.4). Children examined in 2007/2008 (wave 1) (mean +/- SD age: 4.4 +/- 1.1, range: 2-9 years), in 2009/2010 (wave 2) and in 2013/2014 (wave 3) were included. A total of 5112 children (49% girls) participated at waves 1, 2 and 3. For 2656 children with genome-wide data we constructed a PRS based on 2.1 million single nucleotide polymorphisms. Z-score BMI and z-score waist circumference (WC) were assessed and eating behaviors and relevant confounders were reported by parents via questionnaires. Parental concern of overeating was derived from principal component analyses from an eating behavior questionnaire. Results: In cross-lagged models, the prospective associations between z-score obesity indices and parental concern of overeating were bi-directional. In mediation models, the association between the PRS-BMI and parental concern of overeating at wave 3 was mediated by baseline z-BMI (beta = 0.16, 95% CI: 0.10, 0.21) and baseline z-WC (beta = 0.17, 95% CI: 0.11, 0.23). To a lesser extent, baseline parental concern of overeating also mediated the association between the PRS-BMI and z-BMI at wave 3 (beta = 0.10, 95% CI: 0.07, 0.13) and z-WC at wave 3 (beta = 0.09, 95% CI: 0.07, 0.12). Conclusions: The findings suggest that the prospective associations between obesity indices and parental concern of overeating are likely bi-directional, but obesity indices have a stronger association with future parental concern of overeating than vice versa. The findings suggest parental concern of overeating as a possible mediator in the genetic susceptibility to obesity and further highlight that other pathways are also involved. A better understanding of the genetic pathways that lead to childhood obesity can help to prevent weight gain.