The prevalence of obesity among youth in the USA is currently >18% with projections that more than half of today's children will be obese as adults. The growth trajectory of children more likely to become obese is determined by weight in earliest childhood, and childhood body mass index (BMI) tracks through adolescence and adulthood. Childhood consequences of obesity include increased risk of asthma, type 2 diabetes mellitus, orthopedic disorders, and reduced academic performance. Health implications of obesity in adulthood include premature coronary artery disease, hypertension, type 2 diabetes, stroke, and certain cancers, contributing to the leading causes of adult mortality. Early childhood obesity is influenced by prenatal exposure to maternal obesity and environmental obesogens, and is associated with poverty, food insecurity, and poor nutritional quality. New strategies for primordial prevention of early childhood obesity require focusing attention on growth parameters during the first 2 y of life, with support for increasing the duration of breastfeeding, and improvements in dietary quality and availability, particularly the reduced consumption of added sugars. Reducing the prevalence of obesity among adolescent females and reducing exposure to environmental obesogens may reduce the prevalence of transgenerational obesity. The reduction of early childhood obesity could improve population health, quality of life, and longevity throughout the life course.