My family is threatening to give up on me if I don't change my eating habits and weight. Why are they doing this?

My doctor got in my face and called me out for not following the diet plan and exercise. My aunt bluntly told me I don't give a damn about myself and the only thing I care about is whatever I put I my mouth and not watching it. She called me out on my lies and dragging my mom's depression along and Im an adult and I should be blaming myself and she is done arguing with me. She had tears in her eyes because I'm stuffing myself getting fatter. My older brother even said im being selfish for not listening to them and they give a damn but I'm ignoring their concern and kept studding myself with junkfood an now I have type 1 DIABETIES. They threatened to give up if I don't do something. I'm 5'11 and 326lbs. Why is my family being tough on me? I'm just a child. Well 29.