While the advice for ordinary people like you and I is to stick to about 2,000 calories per day, the people who compete athletically for a living tend to need a whole lot more.
Olympic swimmer Michael Phelps would eat as much as 12,000 calories a day, the equivalent of six days worth of food, as fuel for his sport, while plenty of other athletes eat comparable amounts.
It's all about fitting the diet to the person, as most of us will spend our days sitting and walking around, while those who push their body to the limits and have to do a lot of intensive training will need more fuel.
Former WWE star Big Show, real name Paul Wight, once sat down in the talkSPORT studio and told them that at the height of his wrestling career he was knocking back up to 18,000 calories a day.
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As his name suggests the bloke is a big guy, standing at over two metres tall, and made his name in wrestling off the back of his gigantic stature.
For a man like that, you'd expect a diet with more calories in it just because there's more of him that needs powering, but Big Show was also expected to put on a big show in the ring, and needed a body that could do that.
As such, he would often go to McDonald's and place a huge order, and then sometimes go to Taco Bell afterwards for another big serving of something to chow down on.
He said: "My calorie intake back in the day, which was a lot of empty, bad calories, because I used to just eat whatever I wanted in massive amounts.
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"I'd probably say it was somewhere between 13 to 18,000 calories a day. You get Big Macs you know, I get three or four Big Macs and then I get fries, I get a shake, I get apple pies, and probably fish sandwich or two.
"Then you'd go to Taco Bell and get like 20 tacos."
It's not the healthiest or most nutritious diet in the world but when you're as big as the Big Show it can do the job, at least for a time.
"You can do that when you're younger, when you're still going to be big, but as you get older you realise 'Well, I can't really eat like that anymore,'" the former WWE star explained.
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He said that he now feels like 'I eat like a mouse', saying he would have 'about 10 ounces of protein' and some vegetables to 'try to eat halfway decent'.
He recounted how a beef pie with gravy was 'the most delicious concoction' he'd ever had in his life, and after taking two bites he ordered another one.
Topics: WWE, Sport, Food And Drink, McDonalds
Joe Harker