What do some extreme distance runners have in common with the athletes at the Tour de France cycle race? Suddenly, everyone seems to be talking about adopting a high-fat diet.
The idea behind these diets is that when humans enter starvation mode, their bodies are able to switch from burning glycogen, the sugars produced by eating a meal including carbohydrates, to burning stored body fat which is released into the bloodstream as ketones. These extremely low carbohydrate diets are called ketogenic.
The rationale is that there is only about 40 minutes of glycogen stored in leg muscles, which is why runners have to keep gulping down sweets during marathons or they end up “hitting the wall” two-thirds of the way through the race.