The marathon is almost synonymous with the Olympics and has been part of the modern Games since their beginnings in 1896. Running 42.2 kilometres at speed is one of the ultimate endurance events, requiring athletes to burn up huge amounts of energy.

But how much exactly? And in an era of advanced sports science and nutrition, what are the foods that fuel the champions?

Let's find out from two of the best, the current marathon record holders for men and women, Eliud Kipchoge and Brigid Kosgei, who both hail from Kenya.

We've been to meet them as they trained for the Tokyo Games and spied on their eating habits.

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