All responses above make complete sense! I workout at least 4 days a week and give myself 2 days off for several reasons. 1) I get bored with working out, so getting away from it clears my head... have a life! 2) your body needs rest and recovery. It's so important as it helps to restore muscles and then you are ready to get back to working out.
I also mix in cardio so 1/2 hour first with cardio (treadmill, stepper, etc) something to warm your body up and then go another 1/2 with weights. Here is a schedule that I follow: MON\TUES (cardio\weights) - WED(cardio) - THUR\FRI (cardio\weights) - SAT\SUN (rest and recovery).
Again... it all depends on your goals. I also stay away from white processed sugars, white flour, artificial ANYTHING!, no greasy sh!t and eat balanced meals.