Is it possible to run efficiently and burn fat as fuel? Can our bodies only run on glycogen? Do we need to carb-load before every long run or race? Is fat adapted running a reasonable approach to training and racing?
The answers are varied and personalized. On the one hand, yes, it is very possible to run efficiently on fat as fuel. On the other hand, it’s tough to train that way if you’re not mentally ready to do so. Our bodies don’t need to rely on glycogen and we definitely don’t need to carb load before every long run or race.
Every runner is different and every body is different. What works for one athlete may not work for the next. The motto I live by is “everything in moderation,” and that includes fad diets, running and training, and yeah, even chocolate. Having said that, let’s talk about fat adapted running and how it can (or can’t) work for you.
Disclaimer: this post is a very, very brief overview and synopsis of fat adapted running. This is a very in-depth subject area that a lot of writers, scientists, runners, and doctors have researched and published information about. Please do some additional research if this topic interests you. Likewise, I’m not a scientist or doctor. I’m a running coach and a runner and this post reflects as such.
Fat Adapted Running
Carbs and Fats
Before we get into fat adapted running, let’s take a look at how carbohydrates and fats work together to fuel our exercise. Both carbohydrates and fats are the main sources of fuel for our exercise. Glycogen is a readily-available form of energy that’s easy to burn. Energy stores from carbohydrates can fuel high intensity workouts for up to 90 minutes.
Fats, on the other hand, can only be broken down in an aerobic system. That means fats cannot be used by the body for high intensity workouts. Fats can be broken down and used in low to moderate intensity workouts — think easy running miles. In this case, fat can contribute up to 75% of the energy used.
Carbs = fast, sprinting
Fats = long, slow distance
As a brief recap from last week: carb loading is a scientifically proven way to boost energy stores in the body. True carb depletion and loading occurs when the body is deprived of carbs for a few days and then ramped back up again in the days leading up to a race. Unfortunately this is a highly difficult task to accomplish as depriving the body of carbohydrates leads to mood swings, fatigue, and poor overall athletic performance. There are varying degrees to which carb depletion and loading can be accomplished, however, not just the one I described previously and above. Having said that — carb depletion and loading is proven to work.
Fat adapted running, which is what we’re focusing on today, is the theory that training the body to essentially “run on empty” will thereby teach it to use fat reserves as fuel and not rely as heavily on glycogen. This type of training and fueling works but it’s kind of a slippery slope. Since our bodies use a combination of glycogen and fat to power our workouts, being truly “fat adapted” is a bit of a misnomer.
Fat adapted training is usually done by ultrarunners or distance runners seeking to rely less on sugars and carbs and more on fats as fuel. Fat adapted running is also good for people unable to efficiently breakdown the super sweet gels and drinks without GI upset on the race course.
The best way to become “fat adapted” is to run a few low intensity runs in a fasted state. That means waking up and running first thing in the morning, or running a good four or more hours after eating carbohydrates. Of course there are ketogenic diets which restrict carb intake below 50g per day, but I don’t have much experience there and therefore am not comfortable endorsing such a diet.
Once you begin training to use fats more efficiently as fuel, you’ll need to increase your fasted workouts. For example, you may begin your regime with one or two short runs per week on an empty stomach. Once you’re comfortable with that scenario, you may increase your mileage per run, or add another day per week.
A word to the wise: high intensity workout days — track days, HIIT workouts, CrossFit, etc., should not be used as a fasted state day. Remember, high intensity workouts can only use glycogen. It’s the slow and steady workouts that can be trained to use fats as fuel.
Is Fat Adaptation For Me?
That’s a good question that only you can answer. If you feel like you’re unable to break down gels, chews, and sports drinks on the marathon or ultra course, it can’t hurt to try fat adapted running. If you think you’ll be able to train more efficiently in a fasted state, why not try it? The worst that will happen is you won’t feel great. I don’t recommend trying fat adapted running while you’re in the middle of a training cycle, however. Test it out when you don’t have an ‘A’ race looming and you’ve got some time to see what works for you and what doesn’t.
And now for the Running Coaches’ Corner! Join Lora Marie, Susie, Debbie, and myself for the Running Coaches’ Corner linkup every Wednesday. We love reading your running stories, racing tips, and coaching strategies. Scroll to the bottom of this post to add your link!
TALK TO ME!
Do you run fat-adapted?
Have you ever run fasted?