I do not really know of a way to free feed and still watch the diet of one. All my guys eat in their own area (be it a carrier or a separate room) so that the amount that they eat is measured by me. I feed twice a day and this way I can give special food to those who need it and the correct amount to each according to their size. I also know IMMEDIATELY if one is not eating properly, no doubt in my mind as no one else can reach their bowl. Yes, it is an adjustment, to you and the cats, but they CAN learn. (if you want them to)