yah you make a good point, if depends on if your running at high intensity and also depends on if your cutting, bulking or mantaining for example when I run i run for 30min and i get alittle over 5 miles in that so its pretty hard and im cutting so it wouldnt be a good idea for me to run on an empty stomach because i would primarily be using glycogen as an energy store (muscle) and since im consuming cals at a defecit i would probably lose muscle, if your trying to mantain it wont matter for the most part because your body will replenish what you've lost. however if your gonna run 3 miles at 8/9 min a mile then you dont have to worry at all and piece of fruit will sufice