One of our mantras at Uphill Athlete is that athletes engaged in events lasting more than a couple of hours should not leave the fat adaptation stone unturned. Training your muscles to make better use of fat for energy will yield significant performance advantages for all climbers, runners, and skiers. Some of the most pronounced are:

  • The elimination of energy swings throughout the day.
  • Improved recovery between intense efforts, both intraday and from day to day.
  • Improved cognition and fine motor skills when fatigued, meaning improved safety.
  • Reduced need for eating during multihour to multiday efforts, meaning lower pack weight.
  • The ability to preserve limited glycogen stores for intermittent bursts of high intensity.

All of these are positives and none have any downside. The process of becoming more fat adapted is really quite simple, and we’ve made a detailed case for this in quite a number of articles (see list below).

6 Tips for Fasted Training

One of the easiest-to-implement and most effective ways of causing this metabolic shift is to do some, and eventually all, of your lower-intensity aerobic workouts in a fasted state. Following are six tips on how best to do this.

  1. It’s easiest and most effective to undertake fasted training first thing in the morning before you’ve taken in any calories. Having not eaten for about 12 hours, you’ll be somewhat glycogen depleted already. Training in this depleted state will jump-start the fat adaptation process.
  2. Your rate of progress will depend on your history. If you’re highly carb dependent, this process will be slower and a bit rocky.
  3. If you are new to this, start gradually. Try one shorter aerobic base (Zone 1–2) workout and see how your energy holds up. If you struggle with energy during it, do not get discouraged! This is a great indication that you will see big gains from becoming more fat adapted. Once you can manage an hour-long fasted workout, begin to do more of these relatively short, easy aerobic workouts fasted until you find you finish them and are not hungry.
  4. When you are able to comfortably train fasted daily, it’s time to try longer fasted workouts. Take a snack on the first longer fasted workout so you can fuel when you notice your energy levels dropping.
  5. Eventually you’ll be able to handle long days in the mountains with minimal to no fueling when the intensity is low.
  6. Eating right after your workout will speed your recovery.

Adhering to the rules above, along with some minor dietary modifications explained in the articles listed below, will cause a significant shift in your metabolism to favor fat—in just a couple of weeks. The results will please you.

Fasted Training Progression

Here is a training progression that will work for many athletes to get them on the road to being fat-adapted athletes.

Week # Fasted Aerobic Workouts Tips
1–2 1 Apply to shortest workout
3–4 2 Apply to shortest workout + next shortest
5–6 3 Apply to all but the long workout
7–8 4 Include long workout. During long workout, go as long as possible before eating. Bring some fuel for when you “bonk.”
9+ All All aerobic workouts are done fasted from here on out!

Further Reading

-by Scott Johnston

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