I Am The Fattest Person In My Family

My dad is a health nut, constantly exercises and tries to eat healthy. He's in very good shape. My mom isn't around. I, however, am huge now. My clothes never seem to fit and doing small things like walking up stairs or tieing my shoes get me out of breath. My dad almost can't get his arms around me. He at least tries to get me to exercise, diet and lose weight but it doesn't work. I just keep getting bigger.