The world is failing to protect children from the health dangers posed by climate change and poor diet, a landmark U.N. report commissioned by the World Health Organization (WHO) and UNICEF said Wednesday, warning that every child is under "immediate threat."

According to more than 40 of the world's pre-eminent child and adolescent health experts, not one country on Earth is adequately protecting the next generation from the impacts of carbon emissions, the destruction of nature and high-calorie and processed foods.

They said that excessive carbon emissions, produced overwhelmingly by wealthier nations, "threaten the future of all children" and will burden them with additional health dangers, from deadly heatwaves to the increased spread of tropical diseases.

The report, published in The Lancet medical journal, ranks the performance of 180 countries when it comes to child survival, education and nutrition rates. Under these criteria, less-developed nations such as the Central African Republic and Chad perform particularly poorly compared to rich countries such as Norway and the Netherlands. However, the rankings are largely reversed when the impacts of air pollution from per capita carbon emissions were assessed.

Around 250 million children under 5 in low- and middle-income countries risk being stunted due to malnutrition and other impacts of poverty, the authors said. At the same time, the number of obese children worldwide has surged elevenfold since 1975 to stand at 124 million.

Children in some countries see as many as 30,000 advertisements on television in a single year. And despite industry self-regulation, one study showed that children in Australia were exposed 51 million times to alcohol advertisements in just one year of televised sport.