Intermittent fasting is gaining popularity in the health and fitness community. But, does intermittent fasting have any benefit for distance runners?
Intermittent fasting as a concept is simple - you do not eat. That's it. It could be for 24 hours or simply skipping breakfast and consuming your first calories at lunch. Water and Black coffee (at least for me) are the main staples during a fast. With no food coming in, the body is compelled to tap its energy stores for fuel, particularly glycogen and fat. Some organs, such as the brain, can only use glucose for fuel - hence the need to tap into glycogen reserves.
Empirically, intermittent fasting makes sense for distance runners.
- Glycogen is the fuel source distance runners rely on during races. The dreaded "wall" runners hit during the marathon is the point where the body has depleted its glycogen reserves or is unable to breakdown that reserves at a sufficient pace. Therefore, giving your body regular "practice" in tapping into its glycogen reserves - as in during a fast - makes a lot of sense.
- The digestive system is constantly processing food throughout the day. And, it is well known that physical exercise can strain the digestive system (See Article Here). Therefore, giving the gut time to relax and heal makes sense. (In my experience, I would fast after a day of bad eating, GI distress, or unwanted gas. Even a short fast seemed to re-balance my gut).
- Exercising while fasting is not only possible, but helps stimulate the use of fat as an energy source. In distance running, the body relies on energy stores - particularly fat - to reach the finish line. A fat adapted runner will be able to hold pace even as the body depletes more readily available food and glycogen energy. Exercise while fasting (at easy to moderate speeds) helps stimulate this energy system, seemingly helping to refine fat burning as a running source of fuel.
For me, I would 24 hr fast one day every other week. During the week, I would skip breakfast 1-2 times. I'd maintain my morning running schedule throughout.
Give a try and see what happens. Maybe you are only one skipped meal away from a new PR.