This study, performed as part of the international EarlyNutrition research project (http://www.project-earlynutrition.eu), provides a systematic review of systematic reviews on the effects of nutritional interventions or exposures in children (up to 3 years of age) on the subsequent risk of obesity, overweight and adiposity. Electronic databases (including MEDLINE, Embase and Cochrane Library) were searched up until September 2015. Forty systematic reviews were included. A consistent association of breastfeeding with a modest reduction in the risk of later overweight and obesity in childhood and adulthood was found (the odds decreased by 13% based on high-quality studies), but residual confounding cannot be excluded. Lowering the protein content of infant formula is a promising intervention to reduce the risk of later overweight and obesity in children. There is no consistent evidence of an association of the age of introducing complementary foods, sugar-sweetened beverage or energy intake in early childhood with later overweight/obesity, but there are some indications of an association of protein intake during the complementary feeding period with later overweight/obesity. There was inadequate evidence to determine the effects of other nutritional interventions or exposures, including modifications of infant formula composition, fat intake or consumption of different food groups.