I 've spent 3.5/4 years eating nothing except on the weekends (my undergrad). So I would go for 2-5 days at a time without food. Not because of fasting fads or anything, I didn't even know what fasting was. I was just from a very poor family and if I wanted to go for vacations with my friends or party in the weekend or buy a computer I had to save every penny I could. (that's how I bought my first laptop etc). I woul…
One plausible physical explanation for IF is it promotes autophagy. 18-22 range probably doesn't gain much if any AIUI since you system is already running near optimum if you just eat regular times and don't snack around the clock. But older? Maybe the human body takes longer, in general, to switch on autophagy as it ages, and the additional time in the food-gap helps.