Millions of children and adolescents are growing up in environments where sugary drinks, salty and sweet snacks and fast foods, including ultra-processed foods and beverages, are highly accessible and aggressively marketed. These unhealthy food environments are driving nutrient-poor, unhealthy diets and a surge in overweight and obesity among children and adolescents, even in countries still grappling with child undernutrition. The cost of inaction for children, adolescents, families, societies and economies is immense. Unhealthy diets increase the risk of overweight, obesity and other cardiometabolic conditions in children and adolescents, including high blood pressure, elevated blood glucose and abnormal blood lipid levels. These health problems can persist into adult life, increasing the risk of non-communicable diseases, including type 2 diabetes, cardiovascular disease and some cancers. Overweight and obesity are also associated with low self-esteem, anxiety and depression among children and adolescents. Parents bear the emotional toll of their children’s mental health challenges and the financial strain of higher medical expenses and lost income to care for them. Economies throughout the world are already struggling with escalating health care costs and reduced workforce productivity because of rising overweight and obesity. The ultra-processed food and beverage industry holds disproportionate influence over children’s food environments. It shapes what foods and beverages are produced and how they are marketed, especially in settings where government regulation is weak or absent. In pursuit of profit, the industry leverages vast financial resources and deep political influence to resist policies aimed at creating healthier, more equitable food environments. This imbalance of power makes it difficult for governments, communities and families to protect children’s right to food and nutrition.