Increasing evidence from the EU Project EARNEST and many other investigators demonstrates that early nutrition and lifestyle have long-term effects on later health and the risk of common non-communicable diseases (known as ‘developmental programming’). Because of the increasing public health importance and the transgenerational nature of the problem, obesity and associated disorders are the focus of the new EU funded project ‘EarlyNutrition’. Currently, three key hypotheses have been defined: the fuel mediated ‘in utero’ hypothesis suggests that intrauterine exposure to an excess of fuels, most notably glucose, causes permanent changes of the fetus that lead to obesity in postnatal life; the accelerated postnatal weight gain hypothesis proposes an association between rapid weight gain in infancy and an increased risk of later obesity and adverse outcomes; and the mismatch hypothesis suggests that experiencing a developmental ‘mismatch’ between a sub-optimal perinatal and an obesogenic childhood environment is related to a particular predisposition to obesity and corresponding co-morbidities. Using existing cohort studies, ongoing and novel intervention studies and a basic science programme to investigate those key hypotheses, project EarlyNutrition will provide the scientific foundations for evidence-based recommendations for optimal nutrition considering long-term health outcomes, with a focus on obesity and related disorders. Scientific and technical expertise in placental biology, epigenetics and metabolomics will provide understanding at the cellular and molecular level of the relationships between early life nutritional status and the risk of later adiposity. This will help refine strategies for intervention in early life to prevent obesity.