You must absolutly make sure that you are eating enough food and taking in enough nutrients directly after you get done working out.  Dont wait any longer then 1 hour at the very most.  If you want to build more muscle you better follow this rule.  The body is in a state that it will actually suck up the calories and nutrients that you fees it after a workout. Failing to give yourself these nutrients will shorten your recovery time.  You should also be eating foods or a meal 1 hour before you work out also.  This will keep ypour energy up while you exercise.