By Phil Han
London (CNN) - People around the world are watching Olympic athletes show off their physical skills.
But what we're all wondering is how they have so much energy!
The average person needs to only consume around 2,000 calories a day, but what if you were Olympic champion Michael Phelps? He needs to eat about 10,000 calories worth of food every single day.
"Well first of all I guess it's a lot of food and it's a lot of carbohydrates. Looking at this, for what an average person eats in a day, is probably about a fifth of this total amount, what we would recommend people to eat. So it's a huge amount of carbohydrates to get through," said nutritionist Holly Pannett.
[Reporter]: "Well you mentioned the carbs, it looks like mostly just pasta isn't it? Why would Michael Phelps eat a diet so heavy on pasta?"
"Well carbohydrates are, basically they're fuel, the energy source that will fuel your workout. They're really quick, they're fast, your body can break them down quickly, and you have instant energy. That's the benefit of eating carbohydrates over protein really," said Pannett.
[Reporter]: "And my big question is, how could one person possibly fit this much food into their body?"
"That's something I can't answer. I don't know. I guess it takes a few years of practice. But on the other hand if you're doing six or seven hours of training a day, you're gonna be really hungry," said Pannett.
[Reporter]: "So if you're here being an Olympic athlete, how many calories would you normally burn off during training?"
"In the workout? Depending on what sport you're doing. So for swimming, you would burn 1,000 to 1,500 calories per hour of training, depending on the type of training you're doing, which is about half of what a person would normally burn off," said Pannett.