Answer:
ABC stands for Ana (Anorexia) Boot Camp diet. It’s 50 days and the dieter ranges their calories from 100-500 calories a day. There’s also a fast (where the dieter consumes 0 calories) about one day a week. I’m not sure how it started or where it gained it’s popularity, but I had never heard of it until I joined the fitblr community. It’s incredibly dangerous.