Is the Keto Diet Right for Runners?

Most runners know the long-revered basics of running nutrition: Plan a good pre-race meal, eat a protein and carb-rich recovery meal and hydrate well. Then there are diets, like the popular Ketogenic plan, that promises more energy and weight loss. But is the high-fat, low-carb diet for runners?

Brett Osborn, neurosurgeon and nutrition adviser to nutrition and supplement site BPI Sports says yes. “Endurance athletes in particular will benefit from the Ketogenic diet because during long sporting events, their bodies are running primarily on fats and/or ketones,” he says. “So why not go into the race, for example, already in a robust fat-burning state?”

The Keto diet is a high-fat, low-carb diet where the body is forced into Ketosis, a state where the body doesn’t have enough carbs for energy. Instead, the body starts making ketones, which are used in place of carbs for energy. The diet also burns fat for more energy. Others, however, aren’t convinced the diet is the right choice for runners.

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“I’m going on the record saying Keto is terrible for any serious athlete,” says James Fell, runner, columnist and author of Lose it Right: A Brutally Honest 3-Stage Program to Help You Get Fit and Lose Weight Without Losing Your Mind. “Fat is low combustion fuel. When you are engaged in high-intensity activity, you need rapid access to quick-burning fuel. When you have carbs in your system, you get it,” he added.

Fell says runners can use the Keto diet for lower or moderate intensity workouts, but those longer, harder efforts need carbohydrates. “Fat simply burns too slow, so it’s like trying to suck fuel through a straw and it holds you back from a maximum intensity effort,” he says.

Osborn disagrees. The need for carbohydrates may be a “myth.” The preferred energy source is fat, or ketones, he says. “For eons, marathon runners have carbed-up the night before a race, and for what?” he urges. “Nothing. The primary energy source of the body during a race is fat, so why fill up on carbohydrates?”

If you want to give the Keto diet a try, Osborn says you don’t want to start it a few days before a big race. “An athlete should be burning fat and/or Ketones before the race begins,” he says, suggesting that the diet be started months in advance. “Athletes will not suffer, performance-wise, on the Keto diet.”

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Another hallmark of the Keto diet is what’s been dubbed “Keto flu,” where you might feel tried or sick as the body adjusts to the new energy source. Those side effects can last between seven to 10 days. “Stick with it even though you may experience fatigue as your body morphs into a fat-burning machine,” Osborn says. “Show your body its newly-preferred energy source.”

Fell, meanwhile, says the Keto diet may be a fad diet, and he suggests runners find a diet that fuels the body and doesn’t cause any gastrointestinal issues. He says it’s not about choosing the perfect diet, “but rather listening to what my body says I need to perform well … Sometimes it’s best to ignore all the dietary hype and go with what makes you feel good, powerful and energized.”