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Is it a good idea to ultra-marathon on a Keto diet?

by Larry Carroll

If there’s one thing that has been around as long as the concept of running for health, it’s dieting for health. Much like running itself, dieting has witnessed the rise and fall of many fads, vast quantities of products touting the ultimate solution, and many programs that prove difficult to stick with. Nowadays, the hot word in dieting is “keto,” and as more long-distance runners are looking to it for an edge, one has to wonder: Is it a good idea to ultra-marathon on a keto diet?

For decades, the image of a long-distance runner in the days before a marathon was relatively clear-cut: Huddled over huge plates of pasta, shoving a banana in the mouth at the starting line, treating themselves to chocolate milk in an attempt to get sugar back to the muscles post workout. Of course, all these images run contrary to the rise of the ketogenic diet, which promotes a high-fat, adequate-protein, low-carbohydrate lifestyle that forces the body to burn fats rather than carbs.

According to a recent article by CNN (https://money.cnn.com/2018/09/17/news/companies/keto-diet-trend/index.html), “With the help of social media and word of mouth, demand for keto-friendly products have gone through the roof … Interest in keto has far outpaced interest in other fad diets. A Google Trends chart over the past year show searches for ‘keto’ have dwarfed searches for ‘paleo,’ ‘Whole 30’ and ‘intermittent fasting.'”

Naturally, when something the media describes as a “fad diet” hits such pervasive proportions, it is going to bleed over into the world of athletics and fitness. It’s no surprise, then, that someone like Zach Bitter is giving interviews talking about his recent setting of the record for fastest 100 mile trail run while crediting a diet with virtually no carbs.

Remembering his high school and college days, Bitter tells Men’s Journal (https://www.mensjournal.com/health-fitness/zach-bitter-100-mile-american-record-holder-he-also-eats-almost-no-carbs/): “My diet was clean, but probably 60% carbs. Then, in 2010, I started participating in ultra-endurance events and noticed that things weren’t ideal — not being able to sleep consistently through the night, having big energy swings during the day, chronic inflammation in my ankles, things like that.”

After meeting with Jeff Volek, an Ohio State University professor/expert in low carbohydrate research, Bitter changed to a diet that now has carbs accounting for as little as 5% of his diet. “The inflammation went away really quickly, and within a month I was sleeping way better, like getting through the night,” Bitter explains. “And I noticed that my energy levels were consistent throughout the day.”

Whenever any athlete decides to go Keto, the primary question seems to be the same: How can you fuel yourself during an endurance race?

According to Kristin, a blogger at Madcity Eats, it was just a matter of time before her body got accustomed to burning fat, not carbs. “I started training for a 50k after being on the keto diet for about four months At that point, I was fully fat-adapted, meaning my body had shifted into a metabolic state where it was using fat as its primary fuel source.,” she writes (https://madcityeats.com/my-first-ultra-marathon-on-a-keto-diet-eb6e66840cce), observing that the fat in her diet made her less hungry than in past training, allowed her to skip breakfasts and rely on fuel from the previous night’s dinner, and like Bitter led to her recovering from workouts faster. “I know the ketogenic diet is working for me  —  not only in my day-to-day life, but also in my endurance pursuits.”

Much like Atkins and other low-carb diets, keto puts your body in a metabolic state called ketosis. Your body becomes efficient at burning fat for energy, and supplies energy for the brain by creating ketones in the liver. Reductions in blood sugar and insulin levels are common, which can result in health benefits. However, health experts have voiced concerns over ketoacidosis — a dangerous condition that occurs when the body stores too many ketones — which could lead to liver, kidney or even brain damage, particularly in diabetics. Even if you closely monitor your transition into the keto diet, the so-called “keto flu” should have you expecting to feel tired and in some sort of gastrointestinal distress for several days.

Then there’s the matter of a recent study in the Journal of Sports Medicine and Physical Fitness where Edward Weiss, PhD, associate professor of nutrition and dietetics at Saint Louis University, found with some colleagues that participants actually performed worse on cycling and running tasks after 4 days on a ketogenic diet than that same window on a high-carb diet.

“Just losing a few pounds is enough to give you a huge advantage on the bike, but I’m very concerned that people are attributing the benefits of weight loss to something specific in the ketogenic diet,” Weiss tells Health magazine (https://www.health.com/weight-loss/keto-diet-side-effects). “In reality, the benefits of weight loss could be at least partially canceled out by reductions in performance.”

Not exactly music to the ears of an ultra-runner hoping to improve their time on the trail.

Ultimately, Kristin at Madcity Eats may sum it up best: “What I learned is that there isn’t a one-size-fits-all approach to training and racing while in ketosis. Everyone is different and has different fueling needs based on factors like body composition, how long you’ve been fat adapted and the duration of your race. Some athletes can train and race in a fasted state; others need to eat before and during a race. Still others opt to break from ketosis in the days leading up to an event and consume more carbohydrates for optimal performance.”

As the TV commercials say: Consult your doctor. Together, perhaps you’ll decide that keto offers the right path to reach your training goals. But until then, you might not want to throw away all those boxes of spaghetti just yet.

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