Thank you guys. Lots of good information in here. Does anyone else have other articles that are good reads on the subject?
I don't know if you have dug into past threads here on WW but if you search for "fasted" or "fasting" there are probably a half dozen or so decent threads. Some are pretty extended, so will link to a few good sections below, where the conversation gets really juicy, however it is worth reading through them all if you are really interested in the topic. KWalker seems to have a good bit of knowledge and firsthand experience with the topic, and links to some good articles. You asked about fasting training, not low-carb training, however note that the topic is often intermingled with "low-carb" discussions, and "glycogen depletion" discussions because many of the same metabolic pathways will be involved along with many of the same potential benefits/pitfalls. Essentially, they are just 3 different ways to get the body into a carb depleted state, through fasting (short term restriction), low-carbing (longer term restriction), or extended workout sessions followed by intervals (activity based depletion), so that the stressor (energy demand while in a carb depleted state) will provoke an adaption.
I also recall seeing some great articles on the AIS website (http://www.ausport.gov.au/ais/nutrition ... adaptation
) which are valuable in that they are sport focused, as opposed to a lot of the fasting studies out there which are health/weight loss oriented.
In particular, the studies by L.M Burke are interesting in that they seem to find that while you can improve fat burning with fasted training, it can be at the expense of carb burning, so in an effort to boost endurance you will be stealing from your top-end power production. That may be a good tradeoff for some (people doing events 4hrs+), but it suggests that the hype surrounding the "train low (carb) race high (carb)" technique doesn't offer the benefits that proponents claim for shorter events. In other words, it does not allow you to build your fat burning with a lot of fasted training and then add some carb fuel to the mix to supercharge yourself for a hard ride or competition, because your body's ability to utilize that carb fuel will have been compromised if you spend too much time in a carb depleted state.
Some amount carb depleted training has been shown to increase mitochondrial biogenesis though, so for certain people certain people in certain instances it may hold some value.viewtopic.php?f=8&t=135041&hilit=fasted&start=75viewtopic.php?f=8&t=119866&hilit=fastedviewtopic.php?f=8&t=102833&p=877540&hilit=fasted#p877540viewtopic.php?f=8&t=69049&hilit=fastedviewtopic.php?f=8&t=81348&p=713162&hilit=fasted#p713162