The Mexican government is to ban junk food and fry-ups in primary and secondary schools in an effort to combat one of the worst obesity problems in the world.

From the beginning of the next school year, school shops will no longer be allowed to stock fizzy drinks, sugar-stuffed fruit juices, processed snacks, or more local delights such as chili soaked sweets. Nor will school kitchens offer traditional standards such as fried tacos.

“The kids are going to complain, of course,” the education minister Alonso Lujambio told W Radio today. “We are going to start a profound cultural change.”

The ban does not affect junk food vendors who congregate at school gates at home time, although Lujambio promised future efforts to encourage them to sell healthier products.

President Felipe Calderon launched an anti-obesity campaign in January. Public officials refer to Mexican children as the fattest in the world. While the comparative figures are questionable, one study concluded that 26% between the ages of five and 11 were overweight. The proportion of overweight adults is approaching that in the US.

The health minister Jose Angel Cordoba said consumption of fruits and vegetables in the last 15 years had fallen by 40% while consumption of sweetened drinks rose by 50% .

Dependence on junk foods is compounded by falling rates of exercise caused, in part, by chaotic urbanisation that eats up open spaces. Many Mexicans also have a genetic propensity to store fat, as well as to develop diabetes.

The stampede towards unhealthy eating is also visible in rural areas where a recent study in isolated indigenous villages found many cases of mothers who immediately bought their children junk food treats after picking up government anti-poverty hand outs.

The school ban comes after years of resistance from corporations such as Coca Cola and Pepsi. Lujambio praised their new “co-operative spirit” with reference to their diversification into healthier products, including bottled water which is hugely profitable in a country where few trust tap water. “Our hope is that children start demanding other kinds of products,” he said.