An evidence-based review of research on obesity prevention and treatment in youth was conducted to identify successful elements of community nutrition interventions. Guidelines for dietetic practice appropriate to this age group were synthesized. Following a systematic review of English-language research papers published from 1996 to 2009, 63 interventions met inclusion criteria and were graded according to methodological quality, quantity, consistency, and reproducibility. They also were analyzed for common themes and used to develop guideline statements and a practice algorithm. A national panel of experts in community nutrition, public health, adolescent health, academia, and endocrinology assessed the guidelines and the practice algorithm for validity, acceptability, and applicability. Successful prevention strategies are comprehensive, address social and environmental influences, include nutrition education and physical activity, and use schools as a health promotion delivery venue. Computer- or technology-based and peer-modelling strategies are promising, developmentally appropriate approaches. Effective obesity treatment strategies utilize diet plans and behaviour modification techniques, and involve families in intensive, multidisciplinary interventions. Given the distinct needs of this age group, healthy body weight must be promoted through a comprehensive school-based approach. In summary, obesity prevention and treatment interventions should be comprehensive, multidisciplinary, and developmentally appropriate.