So I've been running long distance for about 4 years (2 full marathons, 4 half marathons). My times have progressively gotten better (PRs at ~3:55 full, ~1:40 half). I tend to gain 5-10 lbs when training for a race because I am a carb addict and overcompensate because of added hunger. But this time I'm trying to go low-carb and run a marathon, but I have about 5 months to adapt to it and train.

The question I have is how feasible is it to train for a full marathon on a low-carb diet? I read at least one source that says once my body is fully to adapted to using fat stores for fuel during exercise, I will be fine. The only time fat stores are less than ideal is for sprinting or other higher intensity exercise but steady state cardio at marathon distance shouldn't be a problem.

So any pitfalls to this or advice? What about carb-loading and the energy GUs that I've been using for my previous races and long training runs? Should I stop using those?