Back in 2008, during the Beijing Olympics, we were regaled with stories about the monstrous 12,000 calorie daily diet that American swimming sensation Michael Phelps consumed while gearing up for the Games. Alas, Phelps revealed last month his diet has never been that gargantuan. "I never ate that much," he said. "It's all a myth. I've never eaten that many calories." Although what the Olympic gold record-holder actually eats might remain a mystery, athletes around the world are trying out different meal plans that they believe will help propel them to competitive stardom this summer in London. Here's a look at five of the strangest (and in some cases, frightening) diets.

1. The insanely high-calorie diet

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While nobody actually takes in 12,000 calories a day, some athletes come awfully close. Phelps's swimming teammate Ryan Lochte says he relies mostly on McDonald’s for his meals, translating to between 8,000 and 12,000 calories. Before you freak out, consider that Lochte's diet also "includes salad and fruit." Canada's Dylan Armstrong, a shot putter, requires between 6,500 and 9,000 calories per day. "But it's easy to eat a lot of calories," he told the National Post earlier this month. "I like a lot of salmon. Obviously, beef and chicken. I’m on a high-protein, low-carb diet. I’ll eat five or six times a day."

2. The oddly specific diet

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For American sprinter Tyson Gay to keep up with sprinting champion Usain Bolt this summer, he'll need to be in the best shape of his life. He's been working with EAS Sports Nutrition to design his perfect training regimen. In addition to taking some legal supplements, Gay subscribes to a tailor-made diet provided by a nutritionist who strictly monitors his intake. "I eat 230 grams of protein daily, 308 grams of carbohydrates, maybe 70 grams of fat," he told AskMen this spring. To achieve that, Gay had to adjust to eating six meals a day, consisting of everything from raisins and yogurt to ground turkey and fish. "It’s going to be a diet plan to really set me up to be the best I can be," he said.

3. The 'fruit only' diet

Fruit stand image via Shutterstock

Is the secret to Olympic success in fruits and vegetables? That's what the new "80/10/10" diet claims. It consists of a diet built around 80 percent fruits and vegetables, ten percent protein and ten percent fat. Michael Arnstein, an American marathon runner hopeful began on the 80/10/10 plan several years ago when he read about it, and has taken it to another level since. He writes on his blog, The Fruitarian, about his decision to turn entirely to fruits and vegetables after trying out some other diets, "Veganism is a logical choice. But Fruitarianism is the healthiest form of veganism. There are countless benefits, both to the person eating a Fruitarian diet, and for the world we live in." He assures that he never cheats, either: "A late-night snack might be grapes, mango, or some other more exotic/seasonal fruit."

4. The starvation diet

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South Korean gymnast Son Yeon-jae has one of the strictest diets of any competitors, having to stay in tip-top shape over the next few months and perhaps even beyond. "She practices for seven hours a day, eats a sparrow's breakfast and lunch and skips dinner," reported the Chosen Ilbo in May. Son points out that some of her fellow gymnasts are blessed with an easier time maintaining their bodies. "Western gymnasts have longer limbs, so even if we weigh the same, they look slimmer. As such, I have to weigh less to look as good," she said. Son believes that any hope of medaling, and the burden of raising South Korea to the upper echelons of the sport, will require her to reduce every gram of fat she possibly can.

5. The 'eat whatever I want' diet

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He's the oldest Olympian this year and like many 71-year-olds won't let anyone tell him what to eat. Japanese equestrian Hiroshi Hoketsu was also the oldest athlete at the 2008 Beijing Games, and he has a knack for his training by now. "I eat whatever I want to eat. I think I was born very lucky. I don’t get fat, even if I eat a lot...I don’t care so much about what I should eat or shouldn’t eat and what I should drink," he told The New York Times last month. Unlike most athletes who require a team of assistants to work with them before and during the Games, It sounds like Hoketsu has his whole schedule and regimen under his control. "I normally wake up around 7:30 in the morning and I do a little walk about 25 minutes for stretching, eat breakfast, then go to the stable and ride two horses in the morning, come back, eat lunch. I do some business work for two or three hours, then go back to the stable and either I get on the horse and take her to the farm nearby and walk or I lead her in hand and walk together." Just your typical septuagenarian.