Physiologically it is not possible to target a particular area to reduce fat.The fat loss will be from your overall body including breast fat this can be achieved by cardio or aerobic exercises.Along with aerobics,toning exercise for the chest area is also needed.Toning exercises for upper chest include decline push ups,incline dumbbell flies,incline bench dumbbell press etc,middle chest includes barbell bench press,dips,push ups,narrow grip push ups etc,lower chest includes swiss ball push ups,decline barbell bench press etc.With exercises,diet is also important to be taken care of.