I am doing a discursive essay in school and need a strong introduction is the enough ?

Your first sentence is not grammatically correct. In fact, start with your second sentence which is a question and then go into your answers. The question is powerful. Forget your last question. You are supposed to answer it as you do in the rest of your essay. Answer some of these questions in your essay, why are prices soaring, why are jobs plummeting, who are some bad role models? What do you mean by obesity weighs you down? Do you land on the ground eventually as you keep getting fatter? Of course not, so explain why obesity is a medical problem?