Introduction: Childhood and adolescent obesity represents a concerning global epidemic, driven by physical inactivity, sedentary lifestyles, and inadequate eating habits. Objective: To analyse the effectiveness of interventions focusing on physical activity and nutrition in the prevention and treatment of childhood and adolescent obesity. Methodology: A search for scientific studies published up to January 2025 was conducted using PubMed, Web of Science, and Scopus databases. The keywords used were: Children OR Adolescent AND Obesity AND Exercise AND Nutrition AND Prevention. All articles that evaluated the effect of exercise and nutrition interventions focused on obesity prevention in children and adolescents were included. The search strategy yielded 491 studies, of which 8 met the eligibility criteria. Results: Evidence shows that most young people do not meet the World Health Organization (WHO) recommendation of 60 minutes of daily moderate to vigorous physical activity, which is directly related to sedentary behavior and excessive screen time, factors that contribute to the increasing prevalence of obesity. Interventions that combine nutritional education, increased physical activity, and reduced screen time show efficacy, although current programs often lack long-term sustainability. Conclusion: Comprehensive and sustained approaches involving schools, families, and communities within a health education model are needed. Thus, addressing overweight and obesity as a public health problem requires a multifaceted approach that includes improvements in nutrition, increased physical activity, and education to reduce sedentary behaviors.