I do 36 hours pretty commonly, and by that I mean about once a month, but I never saw the value in going much past that.....the goal of a fast is to be able to produce caloric deficit, without the body having time to slow everything down in response. In my experience, past about 36 hours I start to feel my body adjust to it, and this is not really the point. I feel the extremities stay cold, lose a lot of my (now legendary) cold tolerance, have little energy, listless.....seeing as my normal state is a Tasmanian devil-like ball of energy that believes anything above 30 degrees is T-shirt weather, this is an alarming way for me to feel.
My pattern is to do a long fast with a pretty strong LISS workout on the tail end, whether hiking, snowshoeing, or a lot of outdoor house work. After this is done, I eat a huge meal with as much protein as I can handle mixed with starches to refill glycogen, which at that point is completely wiped out. I will usually only eat that big meal that day though.....next day is a 16-18 hour fast (my norm), often with as low cal as I can go with the willpower.
This produces 4 days that, once I calculate it out, give me a huge deficit.
Day 1: Eat breakfast for once, but keep it low cal. My go to is about 8 eggs and black coffee = 800 cal, top end....start fast
Day 2: No food until late dinner, usually about 7pm after 2-3 hour LISS work (36 hours after breakfast). Eat a ton, but all protein = 2200 cal, - 700 cal for the workout
Day 3: Normal fast, BAS + waldorf tuna salad is my go to = 1300 cal.
Total calories over those 3 days = about 3600
Normal maintenance cals over those days => 2700 a day x 3 days = 8100
My point is that overall deficit, WITH consideration of your body's response to it, produces a better result. In this regimen, there is not such a prolonged purely glucacon-run metabolic state with all of its adjustment corollaries. This pattern is important to almost any meal timing regimen, such as a 5 to 1 severe calorie cutting stretch followed by one "cheat day" where you eat whatever you want.....I did that for 3 months, eating steak or tuna salads twice a day with a protein shake 5 days in a row, then my eat whatever day, and it got me down to almost 6%BF (and was incredibly miserable, BTW). Throw in change-ups and you will get better cut.
As for the mental aspects, that's all up to you
Last edited by TheyCallMeLazarus; 12-22-2013 at 09:46 AM.
"The soul that does not attempt flight; does not notice its chains."