Lol, idk what exactly you're referring to, but improper dieting messes with a lot of things.
Proper dieting requires you to intake a certain amount of calories based on your ideal weight, intake of the proper food groups, and I can't remeber what else. You are to lose less than 5lbs per week, any more than that is too much for your body to handle.
Dieting also requires exercise. They go hand in hand. If you rely on cutting calories alone that is extremely unhealthy, and you can gain back even more weight than you started with because your body is trying to compensate.