Glad to see more skeptics on here. I do 3-day water-only fasts (not intermittent, just 72 hours straight) once a month. I get very little noticeable benefit if any. For me, the benefits are all "soft" benefits - willpower practice, realizing how little I actually need to eat, and very, very minimal fat loss if I walk for 8 hours on the last day.
Do wish all the magic, memory, autophagy, cancer-prevention, more HGH things were true though, but it does seem like they are blown out of proportion if there at all.
I wonder if the difference in experience might be related to how close one is to diabetes. A lot of people are in various stages of pre-diabetes, I've had fasting blood sugar measurements around 110 mg/dl, which is considered pre-diabetic. I've done keto and a little bit of fasting and experienced the seemingly magical effects.
Another possibility is that other people are getting into ketosis and you aren't. For me, the "recipe" to get into ketosis can vary a lot based on how much I've been exercising and eating carbs before I attempt to limit carbs or fast.
Purely anecdotal, but interesting coincidence - walked with friend yesterday, and he knows someone who lowered their blood sugar permanently by doing intermittent fasting. This makes sense, since fasting moderates insulin resistance. There is an ok book about it by a liver/kidney doctor. Can find if interested, don't remember name offhand. I found it to be good even though I am obviously not a fasting fanatic.
Do wish all the magic, memory, autophagy, cancer-prevention, more HGH things were true though, but it does seem like they are blown out of proportion if there at all.