Of course it's harmful. If you vomit like this for a long time, your esophagus and stomach are normally closed without eating or drinking. When you vomit, the liquid in your stomach will flow back to your esophagus and then spit it out. The liquid in your stomach is acidic and will damage your esophagus for a long time. Moreover, even if you don't want to induce vomiting for a long time, eating may also form conditioned reflex vomiting, and you may also get anorexia nervosa. You won't be able to eat or make up for it then.