Nutrition during early development has an important impact on later health, particularly through greater obesity risk, as demonstrated by FP6 EARNEST. EarlyNutrition explores the current key hypotheses on likely causes and pathways to prevention of early life origins of obesity (specifically adiposity) and associated disorders. We bring extraordinary expertise and study populations of 470,000 individuals to investigate:• The fuel mediated in utero hypothesis• The accelerated postnatal weight gain hypothesis• The mismatch hypothesis.Scientific and technical expertise in placental biology, epigenetics and metabolomics will provide understanding at the cellular and molecular level, and refined strategies for intervention in pregnancy and early post natal life to prevent obesity.Using existing cohort studies, ongoing and novel intervention studies and a basic science programme, we will provide the scientific foundations for evidence based recommendations for optimal EarlyNutrition that incorporate long-term health outcomes, focusing on 4 Target Groups: women before pregnancy; pregnant women; infants (incl. breastfeeding); young children.Evidence is produced from animal and placental studies (Theme 1; T1), prospective cohort studies (T2), and randomised controlled trials in pregnant women and infants (T3). T4 covers scientific strategic integration, recommendation development and dissemination, including systematic reviews and behaviour change approaches.A strong multi-disciplinary team of international leaders in the field including collaborators from USA and Australia achieves balance and complementarity.The project’s impact comprises definitive evidence on early nutrition effects on health, enhanced EU and global policies, major economic benefits through obesity prevention and value-added nutritional products, and practical recommendations on optimal nutrition in Target Groups. Wide dissemination will be achieved through active engagement with stakeholders.