I too am more of the "pig out" variety before my MC. Yep, it probably makes it go harder. But it also strengthens my resolve to keep going - I think to myself something like, remember, you had half a pan of rice krispies bars the day before the fast - you HAVE to clean out your body! :)
I overcame my addiction to caffeine thanks to my first MC, so at least during this one I didn't have the horrendous caffeine withdrawal headaches, and I must say it was a HECK of a lot easier.