As the sponsor, McDonald's will be the only restaurant allowed to sell brand-name food at the games, which means Big Macs, fries and milkshakes will be part of their exclusively branded menu.
A spokesman for the doctors group says the Olympics is an event that celebrates the best of athletic achievements and should not be sponsored by companies contributing to the obesity problem and unhealthy habits.
Coca-Cola has the exclusive rights to sell non-alcoholic drinks at Olympic venues and Heineken has been named the games' official beer.
But Olympics organizers are defending their decision to accept McDonalds' sponsorship as a business deal.
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