Background: Childhood obesity has become a significant public health concern over the past 2 decades, posing multifactorialchallenges, including modifiable factors like dietary habits, physical activity, screen time, and sleeping habits. Prevention effortsrequire a comprehensive approach comprising educational interventions, collaboration among multidisciplinary teams, andcommunity engagement. Since schools play a central role in children's lives, they are the ideal setting for promoting healthyhabits. Objective: The LIVELY (Multidimensional School-Based and Family-Involved Interventions to Promote a Healthy andSustainable Lifestyle) study will assess the prevalence of overweight and obesity in primary school children and identify contributingfactors within families. Additionally, it aims to implement and evaluate a multidimensional, multidisciplinary intervention tofoster a sustainable and healthy lifestyle, ultimately working toward preventing obesity in school-aged children. Methods: During the school year, each class will be individually involved in a multidimensional educational interventioncovering the topics of healthy, sustainable nutrition and lifestyle. Children will also participate in a multimedia lab where theywill create an animated cartoon. The lectures will engage them through various methods, including direct instructions, games,and drawing activities, to stimulate and enhance their learning and involvement. Results: Data collection began in October 2023 and will last until the end of October 2024. A sample of 227 children from 14classes was included in the study. The mean age was 8.9 (SD 1.2) years, and 48% (n=110) were males. Among the overall sample,18.1% (n=41; 95% CI 13.7%-23.7%) were overweight, while 5.3% (n=12; 95% CI 3%-9%) had obesity. Males had a higherprevalence of obesity than females (9.1%, n=10 vs 1.7%, n=3, P=.03, respectively). Otherwise, the prevalence of central obesitywas similar between the two (P=.329). Data analysis and the presentation of the complete results will be available after the endof 2024. Conclusions: The study could lead to the structuring of an educational intervention model in school settings aimed at preventingchildhood obesity. Moreover, it could help raise awareness of childhood obesity and help prevent this public health issue. Trial Registration: ClinicalTrials.gov NCT05966051; https://clinicaltrials.gov/study/NCT05966051 International Registered Report Identifier (IRRID): DERR1-10.2196/57509