Got your Olympic diet right here

American breaststroker Scott Weltz isn't big on dessert—he's lactose-intolerant so ice cream is out. But he is a "greasy cheeseburger kind of guy," he said, "cheeseburgers, grease, anything like that, I'm a big fan of."

Few doctors would recommend a fast-food or high-sugar diet, but Olympians don't play by normal rules.

Breaststroker Breeja Larson eats about 7,000 to 9,000 calories a day during peak training, said Diana Harbourt, assistant director of performance nutrition at Texas A&M. The 6-foot Larson doesn't show it. She has 11% body fat. "It's not recommended for women to go below 12%," Harbourt said. "But each individual is different, and she's just exceptional."