Define fasting.
I was talking about not eating every other day. That is a type of fast but it is not a total all out fast. Eating 1 meal per day is also a type of fast. Not eating bread is another type of fast (at el).
I never suggested a long duration fast. I have tried going 2 and 3 days without eating and that was too long. Every other day is fine. Additionally I also noted that if you are feeling famished or hungry on the "fast" day to nibble on some nuts or beans or perhaps a piece of fruit and there are days where I do have to nibble, but not "small meal" nibble, just a small amount. Enough to adjust the feeling.
As for full on insulin rush on eating days, that doesn't happen to me. I do not eat processed foods like granola, or flakey flakes, or really anything I cannot make from scratch. I don't overuse salt, and avoid sugar unless it comes in the fruit or veggie. I also do not eat very many carbs like bread, pastas, noodles etc... BUT, when I do eat bread it is fresh made without the additives and preservatives. If I cannot recognize what I'm eating (a piece or fruit, a chicken leg etc...) I don't eat it. That means... (for example) a production lasagna (laced with every chemical known to practically embalm you over time). Keep it fresh. Keep it as natural as possible. And make water your drink of choice.
I don't have a problem with yo-yo weight from eating every other day, in fact I don't have a problem with losing or maintaining a healthy weight. I work out, lift weights, walking, and stretches. I had to make a lifestyle change a decade ago and "dieting" wasn't working and since I wasn't running marathon's or some other activity of intense nature I figured this out and talked with nutritionists, doctors, etc... It was easier this way than figuring out some diet plan.
Ever try eating everything raw? With the exception of meat that is. I did it for 30 days, veggies and fruit only. My HDL and LDL numbers were remarkably low, the doctor was astounded. It wasn't easy but those numbers were never better. Long duration? Not something I think I could do over the long term.
And speaking of meat, I do eat lean meat, but I only use it as a flavoring and not a main course. Dairy... egg whites and just a little cheese for flavoring. Off the shelf "healthy" flavored yogurt... has as much sugar as a soda... nope.
As for diabetes, I don't have it, but it does run in my family. My dad had it and my sisters have it. My mother did not. Genetics? Perhaps. And yes I do understand the needs of diabetics. The person I was chatting to obviously by the described diet does not have diabetes either. What I have noticed about one of my sisters is that she is insulin dependent and really hasn't changed poor eating practices.
I'll end it here. Believe it or not, just as I don't believe that the standard American diet is remotely healthy, cleaning up the intake and moderating intake (by differing approaches) is beneficial. But eating smaller amounts of the same junk day in a day out does nothing towards meeting nutritional requirement nor maintaining a healthy weight. It really is that simple.
Here's some source material from the American Journal of Clinical Nutrition
First check sources for a definition of the AJCN. You can go beyond Wiki but it's a start:
https://en.wikipedia.org/wiki/The_American_Journal_of_Clinical_Nutrition
Here's a study from the AJCN:
http://ajcn.nutrition.org/content/85/4/981.full.pdf
Even HuffPo UK did a piece. However as I doubt the due diligence of HuffPo on many "researched" articles I choose not to post here.
Anyway... Fast/Not a Fast choose your language. Some call it a 48 hour cycle.