wow lots of replies!
my background has been pretty traditional endurance stuff. ive done a couple xterras, found mountain biking through them, and moved into 12-24 hour MTB races.
all this was done on a pretty traditional diet and training plan. last year i moved, and discovered Crossfit. been at it just over a year. i am currently eating about 85% paleo and have been making steady gains in strength, ect.
but like i said in the OP im running a marathon and a 50 miler with family in the next six months. i plan to continue doing a hybrid WOD meantime, to hold onto as much strength as i can.
im just having fun learning how my body responds to all this stuff, and was curious about the most effective methods to improve fat metabolisim, as ive lost alot of the long distance fitness i had when i was racing MTBs.
thanks for all the good info!!
im also seriously considering doing CF/CFE black box style just to see how it turns out