Leg exercises do not target any of the fat that is specifically located on your legs. In order to get rid of the excess fat, you need to lose the weight. If you don't lose the weight first, and you start leg exercises and there is any fat, muscle will be built underneath this fat. You must then work on getting rid of that fat in order to see more "tone and definition." The only way to lose fat from ANY part of the body is through a combination of a proper diet and cardio exercise.