My two-year-old cat has gained over a pound in three months and developed an obvious rotundness around the middle. I have three cats and I suspect he is dominating the other two (younger) cats by eating their food. If he's been fed and wandered off for a nap then he'll come back to the kitchen when I feed one of the other cats, muscle them out of the way, and eat some or all of their food. Is this a normal cat behaviour?