No, lifting weights at an early age will not stunt your growth. On the contrary, weight bearing exercises promote tissue growth, including bone growth. Bone cells called osteoblasts increase in number when undergoing mild weight bearing exercises. Not to mention that exercises such as this promote physical fitness and burn calories. When you burn more calories during the day the result is that you will eat more because you will be hungrier. Eating more will in turn assist growth of all tissues. Just be sure to eat the proper foods such as items low in fat. Try a balanced diet such as deriving your calories from the major food groups. Look up MyPyramid, this is intake recommendations published by the government.