No, I haven't read this. I tried a version of IF awhile back, but later realized I didn't do it as it was intended. It was the Every Other Day Diet. I didn't actually read the book on that either... didn't have time, but just looked at a quick synopsis.

My understanding was that I could eat 500 calories every other day (fast days) and no limit on the other days. Those "feast" days were usually around (9K-10K). What I later realized was that as a male, I should have eaten 600 calories every other day and limit to maintenance on other days. Of course, I would never have tried it if I realized that. This was during a long plateau (i.e. a true plateau where I was really eating at a deficit, but not losing. I was so frustrated feeling like I was starving all the time. That was acceptable as long as I was losing, but I couldn't stand feeling so hangry and still not lose. This was a compromise over giving up weight loss altogether.

The results? The plateau continued. If you don't know, there are normal fluctuations during a true plateau just like when losing or gaining. With this plan, those fluctuations became much larger - in one case, 9 lbs. gained in just a few hours. I did this for 6 weeks and had no sustained gain, but that is what is expected during a plateau. After that, I returned to a small daily deficit and finally had the "whoosh" 2 months after finishing, which was after nearly 6 months of plateau. I expect that the whoosh would have been larger if I didn't eaten the excess calories with that plan.

I do a 12 hour fast M-F. Basically I stop eating at 9pm and don't eat anything until 9am the next day. This is pretty easy to do since I'm sleeping most of the time. My dr. suggested expanding it to 16 hours to get the full benefit but I workout in the morning and I think eating after exercise is needed. I cannot move dinner any earlier so 12 hours is the best I can do. I have not found that this has caused any weight loss but it does make managing overnight blood sugars easier since my last dose of insulin is taken with dinner at 6 or 7 pm and its mostly done working by the time I go to bed.

I'm down 36 pounds over a long 6 years or so. This is mostly due to pretty modest carb, (20-30 gram/meal max), few snacks unless truly hungry or needed (usually half an apple or pear and some almonds or walnuts). The greatest change happened though, when I went to all plant-based in May 2018. Poof! Dropped 20 pounds over 5 months. This seems to mean I was plopping cheese, meat, eggs, into my mouth because of the old adage these are "free"--but not calorie free as it turns out. Those dense fats were also slowing down my insulin, pretty sure, because my insulin needs have also dropped about 33% (45 units/day, down to 30 units/day). I'm just beginning to practice some 36 hour fasts on many Fridays (finish last meal by 6 PM Thur, fast Friday, then low carb/higher fat breakfast on Saturday morning (avocado toast) and a nice workout that morning to break the fast)--following Fung's work. This has helped me learn what my true basals are--which are remarkably modest in the absence of excess calories. To be honest, I couldn't do these unusual practices if I wasn't on MiniMed 670G pump. Few lows since it just turns itself off when I'm fasting. Interestingly enough, if my BG starts to dip, a cup of black coffee will raise the BG about 20 mg/dL--something we all talk about in the mornings and I see can help when a little bump is needed with fasting. Hmm.