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The idea that you should train while fasting is quite controversial. There are studies both “for” and “against” the idea that this is fasted training is good for body composition. There are many aspects, which should be considered: type of training, results, gender and age, but what can science suggest for endurance athletes looking to improve their performance?

Mixed Results in Studies

When doing a literature search, we could find as many positive outcomes as negative when it comes to fasted training and body composition. A recent study did, however, find beneficial effect of fasted training on post exercise muscle energy stores (glycogen) compared with a fed group. This means that after fasted training, muscles may be more primed for future workouts.

What’s more, fasted athletes increased their cardio capacity (VO2MAX) more than twice as much compared with a fed group after 4 weeks of training. Another study claims that fasted workouts also improve exercise performance and prevents the drop of blood glucose while training.

It is Unclear if this Applies Long-Term to Professional Athletes

The question that still lacks proper explanation are whether same effects would be reached after long term exercise periods with professional athletes. We believe that more studies need to be performed in order to give a fully Evidence Based recommendation to endurance athletes.

Take Home

Fasted workouts may have a place in endurance athlete training routines, as they might make the body prepare itself better for future workouts (more glycogen in the muscles). The increase in cardio capacity needs to be confirmed by further research as other studies show mixed results when looking at fasting and VO2MAX.


Article by team EBT member @ed_someday_1stepleft_dietitian

Sources (DOI):

  1. 10.1152/japplphysiol.00907.2010
  2. 10.1080/02640410500482727
  3. 10.1016/j.jsams.2010.03.002

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