Mom is forcing me to do football!?

Okay so, I've never really been an athletic person and I am overweight. So this summer My mom told me I should do football. I decided I would. BUT my only motivation for doing it is to loose weight. I hate the game of football and don't understand it at all. The first few days of practice were fun and during that time I told my mom I wouldn't quit. However, I am into the second week of it and absolutely hate it with a burning pion! I told my mom and she says that I promised I wouldn't quit, and that all my like I've been hanging around girls, and that I always have an attitude with her, people will make fun of me if I quit (I don't care), And that I haven't given it enough time, and that nothing would make her happier than sitting in the bleachers and watching me play. I want to make my mom happy but I want to do something that I like. It's not like I didn't give it a chance you know? And here's the thing, I don't understand football at all! I know how to play Basketball, Baseball, Soccer, Tennis, And even Badminton! How do I convince her to let me quit? I honestly H-A-T-E football :'(