It is definitely NOT all you need to stay nourished long term, but in the short term during a fast your body will rely on it's fat stores for energy which allows your digestive system to take a break (your liver does most of the heavy lifting at this point, converting fat into ketones as I understand it). You should supplement things that your body cannot keep readily available as much as your stomach can tolerate - I use the "Paleo-Aid" as a mechanism for keeping myself hydrated and my electrolytes in check. Sometimes I will add the contents of a multivitamin capsule into the Paleo-Aid to help make sure I am getting essential vitamins and minerals. Be careful with taking actual capsules as they can be hard on your stomach (painful pressure IME) during a true fast (no calories consumed).
Generally speaking, I made the Paleo-Aid with:
Some form of green/herbal tea
real Celctic salts for electrolytes/trace minerals (should be many different colors, I would avoid table salt, I use Redmond RealSalt)
Fresh squeezed lemon/lime juice if I was feeling particularly tired/groggy for a mini-dose of sugar and additional electrolyte help
Cleanest water you can get your hands on
I usually drink some of this whenever I'm feeling a bit lower than I would consider normal during a fast. I consider it normal to be a little tired, light headed and sluggish during an extended fast. It can also help with hunger pangs.
Good luck - 40 hours is impressive and about the longest I've gone myself so far!
Last edited by jadedgamerx; 03-22-2013 at 09:38 AM.
About Me: Male, 5'9 - SW: 181 (3/27/09), CW: 163.4 (1/08/13), LW: 160.2 (4/12/12) - GW: 145 & 8-9 %BF
"If we do not burn these bodies, we will all be dead of disease in three days. God will understand, my lord. And if he doesn't, then he is not God and we need not worry." - Balian of Ibelin