Even for a Carb-Fueled Runner, Focus on Fat Burning Can Help Your Marathon Times

I realize most marathoners aren’t going to chuck their pasta today try the experiment I’m living out – training for my 10th marathon on an extremely low-carb, high-fat, ketogenic diet. However, I believe that all marathoners can improve their times and decrease the likelihood of bonking at mile 20 by conditioning their bodies to burn fat more efficiently at marathon pace. Here’s how I did that in past training cycles, when I was still otherwise eating a more or less standard runner’s diet. And at the end, a great video from Sage Canaday on how he accomplishes this. Common thread? One has to get over the common (incorrect) fear of fat in the diet. Fat is good!

(And here’s my caveat – don’t change any of your fueling strategies just on my say so; do the research, think hard, and test these ideas extensively in training before applying them to a race.)

1. Run long without fuel. I did many of my long runs last year and the year before with no fuel. That means no bagel or banana before  the run, no gels or sports drinks during the run. Just water. If you are not fat adapted, this can be pretty grueling, but the results are powerful.

2. Eat more fat before runs. I incorporated fat into my pre-run meal the night before all my hardest long run efforts. I had it in my head that this was like throwing some slow-burning log on the fire. And it really worked; at least for me. I had much more sustained, consistent energy during my long runs.  Now a lot of how you’re going to approach this is going to have to do with how tolerant your stomach is of certain foods the night before a run. For me, sometimes this high fat meal was pasta with a cream sauce, other times a big pepperoni and sausage pizza with extra cheese. But I have a cast-iron gut. If you have a sensitive stomach, you may want to experiment with olive oil, coconut oil, eggs, grass-fed butter, avocado and other easier to stomach fat delivery methods.

Here’s a link to story on fueling with fat that rounds up the findings of a study published in the journal Nutrients that validates this line of thinking.

“It turned out that when runners consumed a high-fat meal and carb jelly, their time to exhaustion increased significantly.”

“Researchers determined that eating a high-fat meal before a race boosts one’s fat metabolism during exercise, allowing the body’s carbohydrate storage to be used later during a race. ”

Hmmm… yes indeed folks, it all seems to keep coming back to getting more efficient at burning fat, in this case, by eating fat.

3. Try a short-term carb depletion right before your marathon. This last one means essentially eating the way I do now – but with an end in sight. It’s an old-school idea for marathoning that has fallen out of favor, but I think still has some validity. The idea used to be, if you could totally starve your body of carbohydrate, when you started taking carbohydrate again, your muscles would super-load themselves with glycogen and you’d be able to skirt the bonk. But studies have  suggested your muscles get just as loaded with glycogen without the carb depletion phase, just by carb loading in the last few days before the race. So if that’s the case, some folks say, why bother with the depletion?

Here’s why. Because if you spend seven days (or as I did before Boston last year, 14 days) running your taper workouts, which still include some very intense running, on a low-carb diet in a glycogen-depleted state, you are going to force your body to get more efficient at running in a glycogen-depleted state. Which is the very state that pretty much everyone is going to find themselves in during the last 4-6 miles of a marathon.  I warn you, these workouts will not be pleasant. Even easy runs are going to feel like grinding slogs. But after you carb up in the last few days before your race, you are going to feel like a superhero on the course. (At least I did. Obviously everyone’s got to test these things on themselves.) Using this method, I was still running strong in my last marathon all the way to the finish, ran negative splits at the end, and took a five minute PR.   

As a side note, these days I am fat-adapted, and have been more than three months without consuming more than 50g carbohydrate in a day, and my workouts all feel fantastic, total opposite of how they felt when I was in short-term carb depletion phases.

Biologically, here’s why you want to improve your fat burning ability. Your body stores more than 40,000 kcal of fat, and only about 2,000 kcal carbohydrate fuel. If you’re a marathon runner, you want to be able to get at that 40,000 kcal.

To finish up, here’s an interesting thread debating carb depletion over at LetsRun.com.

And finally, here’s a video from the amazing ultra-runner Sage Canaday on optimizing your performance by utilizing more fat as a fuel. It’s about 15 minutes long and well worth watching. Note that he isn’t an advocate of the low-carb diet I’m doing now (he calls that extreme), so this video should be just as interesting to those of you eating a more standard runner’s diet as it will be to those experimenting with low-carb.

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