Image caption Disney's move is part of a growing campaign to fight child obesity in America

US media giant Walt Disney has said it will ban junk food ads on its TV, radio and online programmes.

The firm, which also runs famous theme parks, said it was setting new nutrition standards to tackle America's growing problem of child obesity.

US First Lady Michelle Obama described the initiative as a "game changer".

However, the new rules will not come into effect until 2015, and much will depend on how Disney defines junk food, correspondents say.

Makers of junk food and sugary drinks spend about $1bn (£650m) a year on commercials directed at children under 12 years.

Scepticism

Disney said that any cereals with 10 grams or more of sugar per serving or a full meal with more than 600 calories would not be advertised.

Sugary drinks and high sodium products would also be off the air, the company said.

Media playback is unsupported on your device Media caption Michelle Obama said Disney was changing its business model to tackle obesity

CEO Bob Iger acknowledged there might be a short-term dip in advertising revenue, but added that the company would adjust and create new products that meet standards.

Mrs Obama, an active campaigner to curb child obesity, welcomed the plan.

"Just a few years ago if you had told me or any other mom or dad in America that our kids wouldn't see a single ad for junk food while they watched their favourite cartoons on a major TV network, we wouldn't have believed you," she was quoted as saying by the Associated Press news agency.

Recent studies have shown that almost a third of America's children are overweight or obese.

Inevitably, there is scepticism about Disney's move, the BBC's Paul Adams in Washington reports.

Still, it is all part of a growing campaign to fight obesity, our correspondent adds.

Last week, in the first move of its kind by an American city, New York Mayor Michael Bloomberg proposed a ban sales of super-sized sugary drinks in restaurants, delis, cinemas and sports arenas.