Used as just one aspect, along with: going cold turkey on snacking at work, switching to black coffee, and doing some daily simple fitness basics (pushups and the like), and ongoing bike commuting [prior to calorie consumption] the consequences over the last 18 months have been dramatic.

The main reason 16:8 IM helped with significant weight loss for me is certainly the "side effect" of significantly reduced caloric intake (thank you CICO). Normalizing to two meals and much reduced snacking has made a ton of difference.

So much so that when I hit my semi-formal "target" (midpoint of the "normal" BMI weight range for my height) I think I am going to have to get conscious about getting enough healthy calories to maintain muscle etc.

I try to make slightly more sensible choices, and exercise some mediocre "portion" control... but haven't switched diet to speak of.

I am a convert. I can see that it's not magic, but, for me at least IM as part of a broader modest trajectory change is turning out to be honestly life-changing.

I did 5:2 for 3-4 years as well, and lost 20kg (~44 freedom units). I did 36 hour fasts, and after a while it just felt naturally, but i'd be lying if i said the fasting days were easy. It gets "easier" but never easy.

I usually took a break from fasting during holidays, and a few years back i never really got back into it, and reverted to my old 16:8 ways. I'd love to see more research on it, but from my own experience, it's nowhere as effective as a regular 5:2 diet.