(CBS/AP)-- What's on the menu at the London Olympics this year? Big Macs, fries and milkshakes. That's right, McDonald's is sponsoring the Olympics, with an exclusively branded menu for the occasion. And British doctors say that's sending the wrong message in a country where obesity is ballooning.
The fast food giant will soon open its largest franchise in the world - a two-story cathedral-like restaurant that seats 1,500 customers - at London's Olympic Park. McDonald's will be the only restaurateur allowed to sell brand-name food at the games and there will also be a separate McDonald's restaurants within the athletes' village - in addition to three others at the Olympic Park.
Alongside McDonald's, Coca-Cola has the exclusive right to sell non-alcoholic drinks at Olympic venues. Heineken has been named the games' official beer.
"It's very sad that an event that celebrates the very best of athletic achievements should be sponsored by companies contributing to the obesity problem and unhealthy habits," Terence Stephenson, a spokesman for the Academy of Royal Medical Colleges, said. The group is calling upon the British government to restrict advertising by McDonald's, Coca-Cola and Heineken during the Olympic Games, which are being held in London from July 27 to Aug. 12.
But that's unlikely to happen. London Olympic organizers have defended their decision to accept McDonald's sponsorship as a business deal.
"Sponsors provide a huge amount of the funding required to stage the games," said a spokesman for the organizing committee in a statement. "Without our partners such as McDonald's, the games simply wouldn't happen."
About one-quarter of Britons are obese and experts estimate that could jump to half by 2030. Obesity and related health ailments cost the U.K. health system about 4 billion pounds ($6.5 billion) every year. Worldwide, more than 1.5 billion adults are obese, a rate that has more than doubled since 1980, according to the World Health Organization.
"These brands are using the Olympics to be associated with medals and svelte, fit athletes," Stephenson said. "They don't want us to think of fat, unhealthy people when we think of their products."
Nutrition advocates in the U.S. also had concern with the sponsorship.
"We would not allow cigarette companies to sponsor Olympic events," Dr. Marion Nestle, professor of nutrition, food studies, and public health at New York University, told HealthPop. "We should not permit marketers of junk food to kids to do so. Sponsorship implies endorsement of junk foods by Olympics committees. That surely is not a healthy message."
Britain is also battling an increasing alcohol problem, which experts warned could worsen during the Olympics.
"When any major sporting event has an official alcohol supplier, it sends out completely the wrong messages to young people, making it seem as though no major event is complete without alcohol," said Sir Ian Gilmore, special adviser to the Royal College of Physicians on alcohol.
He said he "greatly regretted" that the London Olympics had appointed an official beer.
Some experts said advertising during the Olympics could actually cause a spike in fast food consumption, even in people not inclined to eat it.
"We cannot simply decide not to process (an ad), there is a subliminal association that is made that may affect your behavior in the future," Nilli Lavie, a professor of psychology and brain sciences at University College London, said.
McDonald's said in a statement they expected about one-in-10 people visiting London's Olympic Park to eat at their Golden Arches. The company has been an official Olympics sponsor since 1976 and said it would be using its expertise to provide "high-quality British food" at the Games.