Jamie Oliver has criticised sports stars including David Beckham and Gary Lineker over their promotion of "junk foods".
The TV chef, who previously campaigned successfully to improve school meals, joined a collection of senior health professionals and heads of children's groups in speaking out on the eve of the London Olympics.
They each signed a letter to The Times, in which they express "grave concern" over the number of athletes putting their names to unhealthy foods.
"Companies are increasingly using the endorsement of well-loved sportsmen and women to successfully promote unhealthy junk foods to British children," the letter reads.
"We believe it is wrong for athletes to encourage the excessive consumption of such items, which are fuelling poor health and obesity.
"David Beckham is a great sportsman, yet he has endorsed Pepsi. What about the impact of Gary Lineker's association with Walkers crisps? Or the partnership between Mars and the FA?
"Food companies are well aware that such foods have few redeeming nutritional qualities, are able to trigger the so-called 'halo' effect by associating them with sport."
The letter also urges emerging stars of the 2012 Games to avoid such "lucrative" endorsements.
"We would ask athletes to be very conscious of the effect their endorsements may have on the future lives of youngsters," it said.
"Obesity does not just carry physical consequences but serious social and emotional ones too."
Other signatories to the letter include Dr Hilary Cass, president of the Royal College of Paediatrics and Child Health , National Association of Head Teachers president Steve Iredale and Charlie Powell, director of the Children's Food Campaign .