You were made in the image of God. How can that be ugly?
God tells us to love one another as we love ourselves. That doesn't work so well if we don't love ourselves.
"The purpose of having a will that is free is so that we can choose to love." Fr. John Riccardo
Research on happiness shows that once our basic needs for food, shelter and clothing are met, the only thing that truly makes us happier is love and connection with others. No amount of stuff (or thinness) will make us happy.
If love is ultimately our life's purpose, then we must work on loving ourselves. This includes lovingkindness toward your body.