Pretty sure hunter gatherers never fasted. The definition of the verb "fast" is to abstain from food, which indicates a choice. Maybe Grog the caveman noticed his love handles were getting a little big so he laid off the starchy roots for a day or two. But seriously, back in the 90s I was an avid bicycle racer, however I knew that after a 4 hour balls out race I could replace those calories in 5 minutes at McDonalds. You do bring up an issue that is significant, when I wrote "everybody is different", I had a very specific reason. You and me and all who read this have 100s of generations of ancestors who, over time, helped develop our biolgic systems. If you eat and drink wisely (not crazy witholding of food), stay active (I mean really active) and still have Grog's love handles, there may not be much you can do about it (other than surgery). We humans have a set point of stasis, that our bodies will try to get to. I am 6'3" and my body feels good at about 210 lbs. But the next guy who is 6'3" might feel great at 190. The point is, eat reasonably, stay active and don't worry about it, remember you are fighting 100s of generations of ancestors.
