I did Intermittent Fasting (12-16-hour fasts daily) as a weight-loss aid a couple years back. It was okay, but my diet wasn't the best overall (I was working an office job and I would resort to diner food quite often, didn't help much). Lost a bit of weight with it, but nothing outstanding, only like 10-20 pounds from my 350-ish total. (Also did keto/low-carb, same kind of results, minor loss, nothing outstanding. In contrast, last fall, I got my shit together and properly tracked my macros on a daily basis, and dropped 40+ pounds in 4 months, in combination with my ongoing major weightlifting routine.)
As I've gotten more embedded into fitness culture (fitness facebook groups, mostly), the general consensus is that most IF is just another form of calorie restriction, since you can only each so much in the limited feeding window. Most people would be better off just properly tracking their macronutrients. (Same for keto, the supposed hormonal benefits aren't significantly better than just properly balancing your nutrition and regular vitamin intake.)
36 hours is the top-end of the IF range, and those are usually only a once-a-week thing, maybe twice-weekly. Longer fasts than that don't have much in the way of scientific support (few studies, little more than anecdotal evidence in support), and the risk of damage to the system is more likely than the supposed benefits one would gain.
In short, do your homework, make sure what you're doing has some significant support, and more than just anecdotal evidence supporting it.