Aaron:
I’ll butt in here till Rebecca has a chance to respond.
Here is our experience with fasted training. That experience is anecdotal but extensive with literally hundreds of cases both male and female. Rather than look for one black and white/good or bad answer understand that this is a highly nuanced discussion.
1) Most importantly the author, David Roche comes to no conclusion concerning whether fasted training is on the whole good or bad. He does a nice job of presenting evidence both for and against fasted training. But, in the end there is no solid take away for this article.
2) We ONLY recommend fasted training for low intensity session that are below one’s aerobic threshold. We do this because improving fat adaptation at these low intensities will raise many peoples aerobic threshold. By many I mean all but the well aerobically trained. As the article mentions; when one can use a higher percentage of fat at higher intensities that’s a good thing for endurance events. Numerous studies have shown that World class endurance athletes are highly fat adapted.
3) We recommend that athletes train (in Z1-2) on fat but race (meaning any harder workout, race, climb) on carbs. The article correctly points out that lowered glycogen stores will negatively impact performance. So, if the event you are about to undertake will demand higher intensity or even moderate intensity for a few hours AND performance is important to you, by all means you should fuel on carbs, before and during the event.
4) We have seen that the overwhelmingly majority (if I had to guess I’d say 90%) of the folks we interact with are terrible at utilizing fat for fuel. This indicates very poor mitochondrial function. Poor mitochondrial function means poor endurance performance at the very least and at worst serious health issues like type 2 diabetes and other mitochondrial disfunction diseases. So, improving fat adaptation is a good thing for health as well as performance.
5) We see that people doing under about 8 hours of aerobic (Z1-1) work in a week can help jump start their fat adaptation with some fasted training in Z1-2. This speeds up some of the adaptations needed to move that 50/50 fat vs carb cross over point that David Roche correctly correlates with aerobic threshold in most people.
6) At the higher end of the aerobic volume scale we see that athletes doing more than about 12-14 hours/week of aerobic work will be well fat adapted whether they do fasted training or not. I work with some elite endurance athletes who are vegetarian and eat a hagh carb diet but are training in the neighbor hood of 20 hours/week. They are all highly fat adapted and perform very well even in a fasted state. Those high volume trainers will be fat adapted because they will be in a nearly constant glycogen depleted state.
As for the differences between men and women: I am not in a position to make any sort of broad brush pronouncement. However, I can tell you that Roxanne Vogel, who climbed Everest in 2 week door to door from her home in San Francisco, did a TON of fasted training and feels that contributed to her success. You can read about that here.
In summary I would say that each athlete needs to evaluate what works for them. These points I’ve laid out above are just some of the factors that one needs to consider before making blanket statements.
Scott
