Exercise Performance on a Ketogenic Diet

UPDATE 3/17/2013:

As I go back through the blog I wanted to provide "results" of my various musings/self-experiments. This one I think was a failure. I've read accounts of people doing meat-only high-intensity endurance exercise with success, but for me at least it didn't work out that way.

I was able to go on long hikes up very large mountains (Algonquin) without any more trouble than I would have had eating my previous diet, but hiking is almost by definition low-intensity. I was able to play 24 hour paintball games, but paintball is mostly walking around with brief, short sprints or intense action. No problems there. Anything that was mostly aerobic probably isn't going to be an issue.

Biking up a huge steep mountain? Probably wasn't going to happen. Now, when I did Wintergreen on my previous normal diet, I was probably going ~3MPH for the final 7 miles. It was incredibly painful and difficult, and come to think of it I was probably thoroughly bonked at that point and operating mostly in the aerobic zone. But I doubt I could have gotten through the previous 100+ miles on meat alone, at least not at the pace my carb-loaded father was setting.

So, experimenters, don't get fooled by the hype. Everything comes with a tradeoff.

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One of the most difficult transitions I’ve had to make has been mental. I’ve been thoroughly indoctrinated in the carb-loading exercise dogma and it is not an easy thing to escape. There is a huge body of studies showing that dietary carbohydrate is necessary for physical performance, which would give anyone looking to perform athletically pause.

As I’m finding very common in health science, however, there have not been very many studies done on competing hypotheses. Now, that’s mostly because no one can even conceive of there being a competing hypothesis; nothing has been swept under the rug, so to speak. But there is a body of evidence that suggest that carb-loading is not the whole story.

I’ve only been able to find one well constructed study on ketogenic diets and exercise. You can find the full text here. Phinney attempted to gather data explaining the apparent paradox presented by primitive hunting societies which ate close to zero carbohydrates. If carb-loading is necessary for physical performance, the survival of the Inuit and Plains Indians is difficult to explain. Historical accounts of white explorers living on an all-meat diet also become difficult to explain, especially their reported endurance.

Two studies are reviewed. In the first, overweight individuals are placed on a very low calories ketogenic diet for several weeks. They did no physical training during the study except for two treadmill tests. Over the course of the study they lost a lot of weight, and of course performed much better on their second treadmill test, even wearing a backpack weighted according to the amount of weight they had lost.

The second study was of competitive bicycle racers. They spent four weeks on a ketogenic diet while continuing their normal training rides. They reported a decline in energy levels during their first week, which they subsequently recovered. Their sprint ability declined and did not recover over the course of the study while their aerobic performance remained essentially unchanged over the course of the study.

Phinney concludes that aerobic performance up to 65% of VO2 max is not impaired and might be improved by a ketogenic diet, but any significantly anaerobic activity will be impaired. Thus, the diet is not optimal for high activity athletes.

His conclusion does not appear to resolve the paradoxes he sets out to address. How is it that Plains Indians, living on a diet consisting predominately of buffalo meat, created a culture of running and physical endurance if they would be unable to perform on a diet lacking carbohydrates? I’ve tracked a few stories down on the internet (they all come from a book called “Indian Running”, which I’ll have to buy to see where the stories are really sourced from) such as the following:

“In 1876 Big Hawk Chief ran from the Pawnee Agency to the Wichitas, a distance of 120 miles, inside 24 hours. His claim to have run such a distance was not believed. The Wichita chief arranged to ride back with him, sending a relay horse to the 60-mile point so that he could change horses there. Before the 60-mile point, the Wichita chief’s horse was forced to stop and rest, but Big Hawk went on. The Wichita chief eventually reached the Pawnee village before sunrise, less than 24 hours after their start, and found Big Hawk asleep. He had come in around midnight, covering the 120 miles across mountains, hills, and streams in about 20 hours.”

It seems similarly unbelievable that the Inuit exist at all if carbohydrates are required for maximal performance. Subsistence hunting requires punishing physical exertion. Did the Inuit paddle their kayaks at 65% VO2Max? They hunted whales. Whale + 65% VO2Max does not add up.

I think the major confounding factor here is adaptation time and training time. The longest modern study lasted a mere six weeks. Most were only run for a week, which as any Atkins dieter can tell you, is quite clearly insufficient time to adapt to the new diet. Perhaps, with a longer adaptation time and more time spent training under the new dietary regimen, some of the reported ultra-endurance reported by various historical sources could be achieved.

Thus I propose a thoroughly unscientific, n=1, study of exercise performance in very low carb, high fat diet conditions. I will spend the winter lifting weights, with a secondary emphasis on running and hiking when possible. When the weather gets warm, I will begin bicycle training. In August 2010, one year after beginning a ketogenic diet, I will attempt to ride a full century without ingesting any carbohydrates. Given how much pain I was in riding centuries while downing carbohydrate gel and Clif bars, I expect this to be quite a challenge. But it will also be a test of the hypothesis that with sufficient adaptation time, endurance performance should not be hugely inhibited on this diet. Or, it will test my ability to kill myself. We’ll see!