Also anorexic here, BMI 15.6.  My favorite is when people claim to eat like 500 calories a day and say they aren't losing weight. I struggled to restrict to 600 a day because I was starving. The only thing that allowed me to do that for 2+ months was the fact that my eating is disordered af. I think it's hilarious when obviously overweight people claim to have eaten less than that for more than a couple days. There's 0 chance.