Childhood obesity has rapidly increased in Korea during the past 20-30 years. Approximately 1 of 10 children and adolescents is obese. Appropriate prevention and intervention measures urgently need. Obesity prevention starts early in life, i.e., obesity prevention and education begins during the period of fetal development in utero. Behavioral changes are the most positively reflected during pregnancy. Infants should be fed breast milk, and inculcated with healthy eating and behavioral habits during infancy to ultimately establish a healthy lifestyle in children. For achieving a lifestyle and behavior that successfully allow children to overcome obesity, although individual motivation is important, active support of parents and family members is also imperative. Health care providers should also make an effort to actively prevent obesity and take necessary intervention actions. Although the efforts of individuals, family, and healthy care providers are important to prevent the rapid increase in obesity, primary prevention should be encouraged at a higher level. Schools should specifically aim at improving nutrition and physical activity by allocating times for healthy eating, playing, and physical education. Moreover, local communities should provide support by funding for safe recreational environments, such as playgrounds and walking tracks. Public health strategies in community and national policies, such as city planning, food marketing, and advertisements, are required for primary prevention of obesity.