When I was a "fat girl" in my early teens, I was put on a fasting/low cal diet. One day it would be 1,000 calories, the next day, salt free broth and black tea. "Uppers" rounded out my Doctor's healthy 1960's diet, and I was 99 lbs, after 6 months.
Of course I couldn't sit still, think straight or keep the weight off.
Now instead of fasting, I have non-meat days and wish they still handed out speed like it was Vit. C.