I'm a big fan of intermittent fasting and since spring, when I first started to truly implement this strategy of eating, I've been able to make visible progress in eating less "stuff" at work and in situations when I don't really have to eat but crave certain food. Now I' feel comfortable not eating until 04:00 PM without it requiring will power and feeling any discomfort at all. Intermittent fasting is basically not eating 16 hours a day and eating within the remaining 8 hours interval, but I'm going to write a post about it in the future, with more details and personal experiences.
But back to running though... I've tried running fasted for the last couple of runs as an experiment, and I was very surprise that performance and distance didn't drop significantly. I'm not yet dialled in when it comes to my training so it's difficult to appreciate if my performance has dropped at all while running fasted but I do feel a bit less energetic, however I also feel lighter and more comfortable from a gastrointestinal point of view if I'm running on an empty stomach. There is an article saying that it's even possible to avoid the "wall" or "bonking" if you include running fasted into you training. For those of you that don't know these terms basically describe that state that you find yourself when you have depleted your glycogen stores (your reserves of easily accessible energy) and you feel your totally exhausted and almost want to die :)
The main idea of running fasted ( I almost wrote wasted :))) ) is to do it in the morning when your glycogen reserves are low and thus to train your body to utilize fat as energy. To achieve that you should do a low intensity work-out such as a long run. The idea is for your metabolism to get used to burning fat because it is not as easy to get energy from fat as it is from carbs ( like glycogen). Also the article linked above states that a study on cyclists showed that training fasted improved their glycogen storage capacity. In other words they were able to store more "easy to get conventional fuel".
I initially wanted to write a short post about running fasted but the discussion is far more complex than I initially thought. There are questions like: is your performance ( e.g. speed ) affected ?; do you lose muscle mass?; is it worth it if during the race you eat carbs and drink sports drinks? is HIIT ( high-intensity interval training ) more efficient at burning fat?
So as I gain more experience running fasted and try to see how it compares to eating carbs before and during running, and also do a lot more reading on the topic I'll come back with future parts and try to answer as best I can some of those questions. I'm curious about your thoughts and experiences.
Take care,
Adrian