Overweight appears when persistent positive energy imbalances occur for long periods of time. Knowledge of dietary risk factors during childhood and adolescence is needed in order to design preventive measures against the increase in the prevalence of obesity and its consequences but is, however, largely missing. Longitudinal studies in children have not found clear causal associations between energy intake or diet composition and overweight development. Research has been ongoing to develop effective intervention studies for obese children but it is not clear which intervention is the most effective in assisting overweight/obese children to improve body composition without affecting growth rates. The objective of this article is to review the available knowledge on dietary risk factors for the development of childhood obesity, to discuss different dietary treatment strategies, and to propose an evidence-based approach to treat obese adolescents.