thats a good question. i guess losing weight in a healthy way would mean that you are losing it by eating healthy, exercising a reasonable amount, etc. you are not all consumed with dieting. you have some plan for how you are going to go about losing the weight, and a plan for how you are going to keep it off once you get there.

eating disorders would be if you are losing weight either not eating, or by vomitting or taking laxatives; if you are overexercising; if everything you do is related to food. when it begins to have that much effect on everyday life, that isn't healthy. also, if you keep losing weight past a point where you originally thought was going to be the target weight, then that isn't good either.

and then obviously, to determine what qualifies as a healthy weight, then you have to take into acciount the persons height, weight, build, amount of exercising, metabolism, etc.