This study uses survey data from the I.Family Study to investigate the association between adolescent and peer overweight in a sample of adolescents aged 12-16 from six European countries. We find clear evidence of peer effects on body mass index, waist circumference, and body fat, which are stronger among adolescents at the upper end of overweight distribution. We also provide evidence that both consumption of less healthy foods and time spent in leisure time physical activity and audio-visual media are positively associated with similar behaviours among friends. These observations may suggest that peer effects on adolescent overweight operate by influencing friends' behaviour patterns, especially unhealthy food consumption and physical (in)activity.

Because interventions related to diet and other health behaviours are seldom successful and/or sustainable, it is extremely important to identify the individual factors that contribute to a healthier or unhealthier diet. To this end, we use cross-sectional data from the IDEFICS study to analyse the dietary behaviour of children aged between 2 and 9 years in eight European countries. We model the complex nature of these individual factors using structural equation modelling. Our results show that both sedentary behaviour and food exposure are strong contributors to children's dietary choices. However, although we find a positive relation between a healthy diet and weight status for girls, weight status appears independent of diet quality for boys. These outcomes, although they permit no firm conclusions on health policy strategies, clearly suggest that further research based on longitudinal data could provide valuable insights for the design of successful prevention and intervention strategies.