It will get to a point where you will not have the energy to walk a few blocks and you will be unable to retain muscle mass. I started recovering from my eating disorder around 2 or 3 years ago. My memory is terrible but I know that at one point my goal was to eat no more than 600 calories a day (about 4× less calories than I needed), and when I would inevitably eat more than that, I would make myself throw up as much as I could. I wasn't able to sustain this method for long, but even for months afterwards I had so little energy that I was physically unable to stop myself from falling asleep during the day. I didn't lose more than maybe 10 pounds. That made me upset, so I comforted myself by eating massive amounts of food and then regretting it and throwing up almost all of it. It got to a point where I started to enjoy the sensation of puking. I came up with creative ways to induce vomiting when I didn't feel like jamming my hand down my throat. My bulimia led to other risky behaviors. I used to cut myself so much that it would physically hurt when I wasn't cutting. I would steal people's pencil sharpeners and razor blades anytime I saw them. I don't remember when or why I stopped, all I know is that all of this came to a screeching halt one day. Once I started keeping my food down, I started rapidly gaining weight. It's nearly impossible for me to lose weight now because I taught my body not to burn fat. All it can do now is cling onto every nutrient particle that I eat. I am 15 years old and I am 270 pounds. I developed severe obstructive sleep apnea very soon after I started gaining weight and was having around 130 apneas per hour because of my weight. This presented similarly to narcolepsy, I was physically unable to stay awake during the day. I would drop headfirst onto my desk at school. I had to get my tonsils, adenoids, and the little pieces of tissue inside my nose taken out about a month ago just to be able to breathe properly.