American health experts say schools should have to disclose full nutritional details of the food and drinks they serve.

The panel of top US government health advisers is also demanding annual weigh-ins for all pupils and compulsory PE.

The National Academies Institute of Medicine report, delivered to America’s Congress last week, urged the White House to increase its anti-obesity efforts urgently. “We’re calling for a revolution in the way children are raised,” said chairman Jeffrey Koplan, former chief of the Centers for Disease Control and Prevention, the US government’s health advisory arm.

Nine million - 8 per cent - of America’s six to 19-year-olds are clinically obese.

The report blamed the rise in obesity on schools’ curtailment of playtime and gym classes, alongside poor diets, junk-food marketing and sedentary lifestyles.