The global obesity epidemic has been rising for four decades, yet prevention efforts remain limited. Quantitative models have provided insights into the epidemic's dynamics, enabling the integration of evidence from various levels. These models show that increasing energy intake is a major driver of obesity, with significant impacts on future health and economic outcomes. Effective interventions are limited but growing, and cost-effective policies are recommended for implementation. Systems science offers a framework for understanding the complex forces driving obesity, emphasizing the need for coordinated actions across governments, international organizations, the private sector, and civil society. Key actions include improving food and built environments, cross-cutting initiatives, and increased funding for prevention programs. Embedding actions within existing systems in health and non-health sectors can enhance impact and sustainability. Empirical evidence supports the effectiveness of interventions such as reducing screen time in children, counseling programs, and bariatric surgery. However, many interventions lack rigorous economic evaluation. A systems approach is crucial for addressing obesity, considering cost-effectiveness, implementation feasibility, and equity. The ACE studies highlight that regulatory and fiscal interventions are often the most cost-effective. Translating these findings into practice requires adaptations to local contexts. For example, sugar-sweetened beverage taxes have been discussed in the US, while regulations on food advertising to children vary globally. Community-based programs and health promotion initiatives are cost-effective but often depend on sustained funding. International agencies, the private sector, civil society, and health professionals all play critical roles in obesity prevention. Governments need to lead with policies targeting food and built environments, while the private sector can contribute through reformulation and marketing restrictions. Civil society organizations advocate for healthy environments, and health professionals provide counseling and support. The UN High-Level Meeting on NCDs in 2011 emphasized the need for global leadership and coordinated action. Obesity prevention requires multi-faceted strategies across different levels of government and sectors. The integration of systems thinking, cost-effectiveness analyses, and cross-sectoral collaboration is essential for addressing the complex and interconnected nature of the obesity epidemic.The global obesity epidemic has been rising for four decades, yet prevention efforts remain limited. Quantitative models have provided insights into the epidemic's dynamics, enabling the integration of evidence from various levels. These models show that increasing energy intake is a major driver of obesity, with significant impacts on future health and economic outcomes. Effective interventions are limited but growing, and cost-effective policies are recommended for implementation. Systems science offers a framework for understanding the complex forces driving obesity, emphasizing the need for coordinated actions across governments, international organizations, the private sector, and civil society. Key actions include improving food and built environments, cross-cutting initiatives, and increased funding for prevention programs. Embedding actions within existing systems in health and non-health sectors can enhance impact and sustainability. Empirical evidence supports the effectiveness of interventions such as reducing screen time in children, counseling programs, and bariatric surgery. However, many interventions lack rigorous economic evaluation. A systems approach is crucial for addressing obesity, considering cost-effectiveness, implementation feasibility, and equity. The ACE studies highlight that regulatory and fiscal interventions are often the most cost-effective. Translating these findings into practice requires adaptations to local contexts. For example, sugar-sweetened beverage taxes have been discussed in the US, while regulations on food advertising to children vary globally. Community-based programs and health promotion initiatives are cost-effective but often depend on sustained funding. International agencies, the private sector, civil society, and health professionals all play critical roles in obesity prevention. Governments need to lead with policies targeting food and built environments, while the private sector can contribute through reformulation and marketing restrictions. Civil society organizations advocate for healthy environments, and health professionals provide counseling and support. The UN High-Level Meeting on NCDs in 2011 emphasized the need for global leadership and coordinated action. Obesity prevention requires multi-faceted strategies across different levels of government and sectors. The integration of systems thinking, cost-effectiveness analyses, and cross-sectoral collaboration is essential for addressing the complex and interconnected nature of the obesity epidemic.