How can i safely lose weight for ballet?

I have been dancing for a year and a few months now. I have really strong muscles and have gained 12 pounds in 2 years. I am lean and a bit short and wanted to lose weight, maybe a pound for ballet because lately ive been feeling a little bit less lean and partly is because of my muscles but i still want to lose a little weight. I am 13 years old and besides wanting advice in losing a little weight i would also like to know what to eat before practicing ballet for about 2 hrs, i want it to be light and yet give me energy to dance... Please help!