I am pre-op, but have read that the hunger can be stomach acid to be relieved by prilosec or something of that sort. Also, when you are hungry, drink water. It often is a signal that you are thirsty or dehydrated (that goes for pre-surgery hunger, too).
To avoid snacking, consider setting a schedule for consumption, i.e., your surgeon suggests 4 meals a day, so eat at 8am, 12pm, 4pm, 8pm (or whatever works for you, of course). If you feel hungry between those hours... drink water. Sometimes making rules to follow can help us follow our own guidelines, rather than being without boundaries.