The World Health Organization is to call for strict controls on junk food in a major campaign against obesity. The agency will unveil the strategy next week after evidence that obesity has become a global epidemic that is directly linked to more than 30 million deaths each year. The WHO believes that obesity is now one of the world's three greatest health threats, along with smoking and malnutrition. Recent estimates suggest that 1.7 billion people are now overweight, leading to a surge in diseases such as cancers and diabetes.