Is the High-Fat, Low-Carb Ketogenic Diet Right for You?
By: T.J Murphy
Sep 19, 2016

The diet has quietly become the rage among ultra-endurance athletes and elite soldiers, and it’s a surprisingly yummy way to fuel up.

In the past several years, as measured by Google Trends, interest in an unusual style of eating called the ketogenic diet has tripled, and chances are you have a friend or coworker who’s tried it. Early adopters are typically people who run or ride a lot and want a food plan that doesn’t just fill their tanks but also boosts performance. Followers scarf eggs, cheese, and olive oil in hunger-killing quantities, turning their backs on just about every carb other than vegetables. They don’t use half-and-half in their coffee—they use heavy cream. Still, they’re likely to look a little lean, since the ketogenic diet turns them into 24/7 fat burners. (Even while surfing the couch.) And don’t be surprised if they report feeling better and stronger than ever.

Ketones are a type of organic substance that includes ketone bodies, a collective name for the three molecules that are produced naturally by the liver when it breaks down fat for energy, a process that the ketogenic diet jump-starts. Under normal circumstances—that is, if you’re eating a standard, balanced diet—your body gets most of its energy by turning carbohydrates into glucose, which cells then convert to energy. If you significantly re­duce carb intake (typically to less than 50 grams per day), your body undergoes a funda­men­tal change: it starts relying on fat-generated ketone bodies as its primary energy source. The brain, heart, and muscles can all burn ketone bodies effi­c­­iently if you’ve been eating this way for a month or so. This metabolic state is called ketosis.
A Day in Food on the Ketone Diet
How endurance athlete Patrick Sweeney puts away nearly 3,000 calories a day on the ketone diet.
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Historically used as a driver of weight loss, carb ­restriction has recently gained favor in ultra-endurance circles and the military’s Special Forces. The idea is to radically crank up fat burning so that athletes and soldiers are in ketosis during grueling, survival-like situations. The biochemistry of how ketone bodies aid performance is complicated, but the processes and benefits are summed up well for laypeople by Dr. Ken Ford, a ketones expert who runs the Florida-based Institute for Human and Machine Cognition (IHMC), a nonprofit research outfit that’s funded by organizations like DARPA, the National Science Foundation, and the Army, Navy, and Air Force.

“During ketosis, the liver produces ketone bodies that are converted into substances that feed cellular energy production,” Ford says. “So basically, an athlete in ketosis can access additional fuel. Though there’s no scientific reason to believe that a ketogenic diet would increase anaerobic power or muscular strength, there is reason to believe that aerobic capacity and muscular endurance could be improved when sufficient ketone bodies are present to complement glucose.” The upshot is that for lower-intensity, longer-range exertion, ketone bodies offer the physiological equivalent of solar power.

There’s more. Ketone bodies apparently switch on specific genes responsible for a flurry of molecular upgrades, enhancing health and lengthening lifespan. Scientists are now investigating their use for treating everything from traumatic brain injury to cancer.

This broadband interest is new. The diet itself isn’t. Ketosis got a foothold in medicine in the 1920s, when it was used successfully to treat children with epilepsy who didn’t respond to drugs. Labeled the hyperketogenic diet, the regimen gave patients 90 percent of their daily calories from fat to help prevent seizures. “No one knew how it worked,” ­Nobel Prize–winning biophysicist Rod MacKinnon says. “They just knew it worked.”

More recently, there’s been a keto buzz among endurance athletes. It started in 2012, when Timothy Olson, a runner who follows a ketosis-friendly diet, broke the record at the Western States 100, the rugged, revered annual trail race in the Sierra Nevada. Last year, Zach Bitter, another ketones-adapted runner, set the American record for 100 miles on a track—11 hours 40 minutes 55 seconds. Data from a study conducted by Ohio State human-sciences professor Jeff Volek showed that ­during Bitter’s runs, as much as 98 percent of his energy can come from fat and only 2 percent from carbs. Your body can store a maximum of around 2,500 carbohydrate calories. But if you’re carrying around, say, 25 pounds of stored fat, that’s the equivalent of roughly 100,000 potential calories. So a fat-adapted runner can, in theory, chug along indefinitely.