Nutrition-related diseases caused a loss of over 56 million years of healthy life of European citizens in 2000. I.Family will make a significant contribution to reduce this burden by studying the interplay and impact of the main drivers of dietary behaviour and food choice. It will take advantage of the unique opportunity to follow-up the large IDEFICS children’s cohort to not only provide added value by maintaining the existing cohort but also, exceptionally, assess the dynamic nature of causal factors over time and during transition into adolescence. The project’s acronym indicates its focus on the individual and its family. By re-assessing children and their parents I.Family will compare families who developed or maintained a healthy diet with those whose diet developed in an unfavourable direction to study the impact of biological, behavioural, social and environmental factors on dietary behaviour over time. Focus will be on the family environment, socio-behavioural and genetic factors determining familial aggregation. Subgroups with contrasting dietary profiles will undergo an enhanced protocol including measurement of brain activation, expression of genes related to food choice, biological and genetic basis for taste thresholds, role of sleep, sedentary time, physical activity and impact of the built environment. I.Family will also link health outcomes like body composition and cardio-metabolic markers to diet and interacting factors to determine their prognostic value. Thus I.Family provides strength of methodology, breadth of coverage and depth of investigation across the ecological model. Guided by research on ethical implications I.Family will be deriving effective communication strategies to empower European consumers to induce behaviour changes, supported by novel web-based, interactive personalised feedback on dietary behaviour. By building on existing success I.Family will take the research on dietary behaviour to the next level in a short time frame.