There has been quite a bit of research into alternate day fasting and 2-3 books written about it. It all (that I know of) looked at it from a calorie perspective and the ‘plans’ allow some food (usually 500 calories) on the fasting day.
Go to Amazon and search for alternate day fasting and you will get plenty of results. The book by James B Johnson was my first ever exposure to the idea of IF. His plan is commonly called the JUDDD Diet.
I did this for awhile, and then did it less, like 3 out of 7 days.
The good news: it did actually reduce my weight.
The bad news: before very long I ended up on the see-food diet, apparently because during my days NOT fasting (which is >24 hours because if you eat till 7pm Mon and start again at 7am Wed, that is 36 hours) I simply could not eat enough for my body to feel nutrient replete. I ended up totally offplan.
This does not mean it isn’t a good thing to try. It means if you do, be sure you eat enough food/nutrients on your food days. That is usually the thing that gets me in my various plan attempts. Not that I can’t eat less or fast. But that I don’t eat enough when I should, and then eventually fall off totally when deprivation kicks up my eat-everything-to-get-nutrients response.
I’ve tried it too and was fine fasting Monday, eating Tuesday, fasting Weds, eating Thurs - then I couldn’t face fasting Friday and felt like I needed to eat everything. Gave up after a couple of weeks trying.
I did ADF. I definitely lost weight in a slow stairstep way. Probably losing fat but who knows. It is very very important to feast on your eating day. Otherwise your body starts getting calorie deprived which screws up your metabolism. Go for it!!! It does help.
Why not call it alternate day feasting?
Based on @gjideofor Gayle’s important insights into psychology (above). And @Bellyman Brian did point out the concept appeared more psychological than a true concern of deprivation.
This is the IDM Protocol from Dr. Jason Fung if it helps anyone having it printed out.
That looks like a great schedule, but I like to do 36 or close to. Join us on the ADF club. 
I asked this on another thread too, but do you have a target cal/carbs etc that you aim for on feasting days? I feel like I morph back into 1,200 cal a day which is a deficit. I think that might not be a good idea?
I know you must eat more. I normally consume around 1500 cal. On a feasting day I shoot for 2000 or more. I eat three meals because it’s hard for me to eat 2000 cals in a keto vein. Back in the day a double whopper and extra large fries plus a full sugar Coke would certainly put me over the top. But if you’re eating keto foods it’s a bit harder
lol I’m with you re. whopper! My problem is cheese slices. I could eat a mountain of them. That and HWC.
I think people in general eat way too much to begin with (3 meals a day and more; who said that you must?) so skipping a day would not be what I would consider fasting per say but giving insulin a rest and keeping it low.
The longer you go without eating the easier it gets from my own experience and is normal for me because I count by the hours until I’m actually hungry again and not by days, a day could be a big deal to some people and go by my own natural circadian like rhythm to avoid purposely starving myself, and try to feel the subtle biological ques between starving (body holding onto fat stores for dear life) and just being a little hungry.
If you eat when glycogen storage is half full you go into neutral mode where your not gaining nor burning body fat for fuel. If you can drain glycogen completely then the body goes after adipose storage but then refuels on that also, so if your eating while refueling then start eating again you just stored what you burned so the longer you can go without eating and feel comfortable the more body fat gets burned on the second round.
You have to adapt to it and pretend you never know when you will be fed next like a prisoner of war.
