How long were the fasts you took? I am curious because my lifts suffer when I have not eaten breakfast, and I'm pretty sure it's because of the exhausted feeling in my muscles, which I attribute to the lack of food.
I fast every day, 16-19 hrs at a time. I train completely for strength rather than endurance, so lift super heavy for 4-5. Max 2-3 sets. If you are going for muscle endurance (8reps+) then some food prior to training.
I have seen only improvement in my lifts since I started this regimen. Lost some serious bodyfat % whilst gained muscle.
Low level of testosterone found to be one of reasons of men's depression.
It has the additional benefit that it alters your mood, aerobic exercise makes you happy :)
Strength training may boost testosterone, but the effects of aerobic exercise is well established. Several comparisons have been done between aerobic and strength training and the conclusions have been that strength training have little effect on executive function.
My source for this is the book "Brain Rules" by John Medina [1]. Also check out his presentation on exercise [2] and his Authors@Google talk [3].
[1] http://www.brainrules.net [2] http://www.brainrules.net/exercise [3] http://www.youtube.com/watch?v=IK1nMQq67VI
(Thanks for the citations. That's awesome, and I wish more people would do it.)
That is one definition of fasting, I guess a lot of people are only exposed to the story of Jesus "fasting" for 40 days where he ate nothing at all (if I remember the story right, if I have that wrong please correct me, I don't know the Bible all that well).