I just saw the documentary "Walking the Amazon" and was blown away. The guy spent 2+ years walking in really tough conditions carrying a ridiculous amount of weight. Started off as a pair, but the other guy got ticked off and left so he continued on with just his guides. Evidently most of the food was from the jungle and he didn't seem to be all that skinny at the finish like many AT thru hikers, so I guess he was able to get enough calories. Had lots of hi-tech stuff, gps, satellite broadband, laptop, rafts (!) so I'm amazed he didn't physically break down. Maybe the book has more details on the equipment and logistics, you know, gear talk!
http://www.edstafford.org/walking-the-amazon