Low carb, high fat (LCHF) diets and the runner
by on Thursday, March 19, 2015  (3 comments)


A little over a year ago, a coworker asked me for some advice. He was struggling with his long runs in preparation for the Boston marathon. We talked through things and all seemed fine. Then he mentioned that he had been trying the Paleo diet. While he had lost weight and was handling shorter runs at relatively low intensity well, he just couldn't sustain for his long runs.

Low carb, high fat (LCHF) is the latest trend in the diet world. Interestingly, it has not just your typical snake oil salesmen pushing it but it has some high profile names, most notably Tim Noakes (of Lore of Running* fame) promoting it. I greatly respect Noakes but, in this case, I couldn't disagree more.

The idea behind LCHF is that it's the way our ancient ancestors ate. This is very likely true. Study evolutionary biology and it's pretty clear that one of the key points of differentiation between our ancient ancestors and other primates was our diet. We hunted animals and ate meat and fatty tissue, not just roughage. However, research suggests that these early ancestors also foraged. They had a balanced diet of both meat and plant-based foods.

Further, modern distance runners competing in events of the marathon distance or shorter aren't persistence hunters. Persistence hunters would run/walk long durations at relatively slow paces to keep animals moving, with only occasional surges at faster paces. They weren't running at a maximal pace for relatively short periods of time. They were running at paces that would allow them to use fat efficiently.

As competitive distance runners, on the other hand, even if we train our bodies to burn fat as quickly as possible, we're not going to be able to sustain 5K pace or even marathon pace. We need glycogen stores to accomplish that. We're different athletes performing different tasks.

There may be an argument for ultra runners to go LCHF but, for those of us who are running distances of marathon or less, the evidence suggests we're better off eating quality carbs.

An important note here, though is the word quality. I'm not telling you to eat highly processed foods and drink sugary drinks. Go with the quality carbs. Fruits and vegetables, starchy natural foods, whole grains. Those should be your primary fuel sources. The truth is that these LCHF diets do have some basis in the fact that we do eat a lot of junk carbs and getting those out, in favor of quality calories of any kind but including quality carbs, would benefit all of us.

As for my coworker, I encouraged him to eat more carbs at least in the day or so before his long runs to fuel those efforts. He did so and his long runs got much better. He ran well at the Boston Marathon and, while still limiting his carb intake, seems to be finding a better overall balance.

*Note: In the interest of full disclosure, the link to the book Lore of Running is an Amazon affiliate link. If you use that link to buy the book, a small portion of the sale will help pay the bills at HillRunner.com. As always, use the link if you wish and thank you for the support.

Photo credit: phil.lees, on Flickr

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Julie (Guest)

Thanks for this article. I 100% agree, both from what I've read and personal experience!

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Thank you Julie. I'm glad you found this useful.

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I've received a couple emails since posting this insisting I was wrong that you can't train your body to sustain marathon and even 5K pace.

Please read this before sending me more angry emails.

In short, if you weigh 176 pounds, you can train yourself to maintain roughly 10:18 per mile (4:30 marathon pace, 32:00 5K pace) on fat. If you weigh 132 pounds, you can train yourself to maintain roughly 7:06 per mile (3:06 marathon pace, 22:00 5K pace) on fat.

While those may not be bad times for recreationally competitive runners, we know without a doubt that it's possible to go much faster with glycogen as fuel.

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