Set a very specific feeding schedule and feed each cat in a separate room. They don't have to have food left out all day for them. Decide how much each cat needs at a serving (breakfast and dinner) and what time of day you can consistently offer both. Put each cat in its space with its dish of food...give them 20 minutes to finish...and then take up whatever is left. Don't give them anything else to eat until their next feeding time. If they're used to having food left out all the time, they may not eat a whole serving at once...but after just a couple times of having it taken away, they'll get the message and eat quickly.