There is increasing evidence that environmental factors in early life predict later health. The early adiposity rebound recorded in most obese subjects suggests that factors promoting body fat development have operated in the first years of life. Birth weight, growth velocity and body mass index (BMI) trajectories seem to be highly sensitive to the environmental conditions present during pregnancy and in early life (“The first 1000 days”). Particularly, nutritional exposure can have a long-term effect on health in adulthood. The high protein-low fat diet often recorded in young children may have contributed to the rapid rise of childhood obesity prevalence during the last decades. Metabolic programming by early nutrition could explain the development of later obesity and adult diseases.