People love throwing the "starvation mode" around when confronted with the fact that the only way to lose weight (unless you exercise a lot) is by eating less. Here's the thing:  I used to be anorexic.  Like an actual diagnosed anorexic who went through treatment.  I had symptoms like purple-ish digits for a while, but I never experienced any major symptoms until I'd been sick for a few years--things like hair falling out, skin getting acne-ridden, etc.  Your body can take a lot of abuse; it really is an amazing machine. I now weigh 130 pounds (I'm a 5'8 girl) and really eat whatever I want (in moderation) because I'm quite active in the cycling community and lift weights.  For a while I put on weight pretty rapidly right after I started treatment (obviously), but after a couple of weeks it tapered off.    tl; dr: "Starvation mode" is an actual thing, but it takes a long time to get there.  You aren't going to go into stasis by eating 1500 calories a day for a month. I hate fats who talk about anything related to anorexia.  They have no idea what the fuck they're talking about.