PepsiCo, one of the world's largest soft-drink makers, has introduced voluntary restrictions on its advertising to children, in response to rising levels of obesity in the US and western Europe.

The company, responsible for brands such as Pepsi-Cola and Doritos chips, has also placed limits on the portion sizes of its products sold in US schools.

The measures are the latest by food and drink producers to prove they can be trusted to regulate themselves, amid mounting pressure on governments to curb obesity. The European Commission has threatened to ban food and drink ads to children if the industry doesn't change its behaviour and the British Government is considering red warning labels on fattening products.

PepsiCo executives and officials told the FT that the company was no longer advertising its flagship cola to children under 12 or its Cheetos chips brand to under-eights. The policy had been in place for several months but the company decided against announcing it publicly - in contrast to Kraft, another US food group that grabbed headlines in January by saying it would reduce its advertising to children.

"Our intent is not to just beat our chests and try to take credit for what we're doing," said Irene Rosenfeld, the chief executive of Frito-Lay North America, PepsiCo's snacks unit. "We're just quietly doing it because it's the right thing to do."

She said the company had replaced its fried Cheetos with a lower-fat baked alternative in elementary schools and limited serving sizes for all snacks to 150 calories, rising to 300 calories in middle schools. But critics say food and drinks companies can still target children via indirect marketing, such as endorsements by sports or pop stars and product placements in films and TV.