The Next Experiment: Low-Carb Endurance Training

Well, the Stone Cat 50 Miler is behind me and I’m eight days into a solid stretch of recovery. No running for two weeks, just cycling and core workouts. Then light running and cross training for a while until it’s time to start training for Boston. It’ll be an exciting, rare halcyon stretch of physical sloth; to my mind that’s the perfect time to start to lose the 10 or 15 pounds I’ve wanted to drop for a couple of years. Counterintuitive? The trick is, I have a hard time losing weight and training hard at the same time. Hard training demands lots of fuel, especially when it’s a hard training schedule combined with a busy work schedule and a big rambunctious family! I’ve got no headspace for dieting under those conditions.

I ate what I wanted the day after the 50 miler, and then Monday morning dropped into a fairly strict high-fat, low-carb eating style. I say *strict* but what does that mean when you can have bacon and eggs with cheese and guacamole with an awesome salad on the side for breakfast? This is pretty easy for me, I love the food choices, and I feel light and sharp once I’m in the groove, and it’s a familiar enough diet now so I can get into the groove pretty quickly.

Anyhow, I mentioned “experiment,” and I don’t mean whether I can lose 10 pounds with an Atkins type diet. I know that’ll work. What I want to find out is whether I can perform just as well or better on a low carb diet, including during long runs and races, as I did on carbs.

The idea is that once you are adapted to burning fat versus carbohydrates, you have far deeper fuel stores to call upon during endurance training. Bonking in a marathon happens when your muscles run out of glycogen (sugar) and brain and muscles have to transition to burning fat for energy. This transition is pretty unpleasant if your brain and body are used to burning carbs primarily. Most people have enough glycogen to run about 20 miles. They often bonk at 21, last miles of the marathon are horrible. I’ve had this happen a few times, avoided it most times. Conceptually, this won’t happen if you are fat adapted.

I’ve practiced — over several seasons running — long runs without taking in any sugar (Gu, sports drinks, etc.) or any fuel at all, just water. The goal was to train myself to be more efficient at burning fat, and it’s definitely helped take the sting out of the last miles of the marathon. But I’ve never tried a whole training cycle on a high-fat low-carb diet – essentially training in ketosis.

Why try it? A few reasons:

  • I’m ever more convinced sugar and unrestricted carbs are at the heart of our national obesity crisis
  • Research shows a high-fat low-carb diet is heart healthy (Dr Aseem Malhotra, writing in the British Medical Journal says, “saturated fat from non-processed food is not harmful and probably beneficial”
  • I enjoy the consistent energy levels and sated feeling a high-fat diet provides, no hungry horrors where you end up wolfing down whole bags of chips when you really just wanted a handful
  • I think if I can get 10-15 pounds lighter I’ll be able to shave some serious time off last April’s 2:58:43 marathon
  • I think I can shave even more time off if don’t have to worry about bonking!

And why do I think it might work? Well, I got interested in this years ago by trying and succeeding with the Atkins diet. Which led me to Weston Price. And leading on to the running end of things, I’m going to refer you to the work of Prof. Tim Noakes, who wrote the Lore of Running and has in recent years become an ardent low-carb advocate, and The Art and Science of Low Carbohydrate Performance by Jeff Volek is a dietitian-scientist, and Steve Phinney, a physician-scientist. And of course, as mentioned in a recent blog post, Vinnie Tortorich‘s book Fitness Confidential and his Angriest Trainer podcast have provided highly entertaining reinforcement of the concept (I wrote about these a few weeks ago).

Results so far? Feeling good, energized and four pounds lighter than I was a few weeks ago.

Benchmark races will be:

  • Boston Prep 16 Miler,  Jan. 26
  • Boston Marathon, April 21, 2014
  • Pineland Farms 50 Miler, May 25

Goals will be to beat benchmark times on the first two courses and come in around 8 hours on the 50 miler, which will me a sub 1:51 on the Boston Prep course and sub-2:58:43 on the Boston course. I’ll let you know how things proceed!