As I remember Atkins, he doesnt want most people to fast per se. Yes, over night, from after dinner to breakfast. And as interest in eating decreases, that first meal may be lunch and breakfast skipped completely.

Other wise I only remember fast fasts. FF's I dont hear that term used any more.

IF is a new thing.

Also the risk of decreasing muscle mass and the need to protect the muscle comes into play.

I am unclear on the issue at this point. As in how long the fast is and it's negative impact on muscle mass. When muscle sparing comes into play, etc.

I think of the prisoners of WWII, people reduced to skin and bones thru starvation.

I personally think" what is my purpose in weight loss?" FOr me it is better health. And abject starvation is not appropriate for that purpose.