I have found upping your water consumption will help a lot. A rumbling tum will usually mean that you are craving some water, or actually hungry.
Drink at least a litre of water before 12 noon, if you work a normal 9-5 shift. It’ll get you off your seat nipping to the toilet at the very least!
Also, it’ll stop the nagging feeling that you are hungry. I brought my cereal into work so that I commuted to work via train, got in early and then settled down with a bowl of weetabix before cracking on with my work.
If you keep to a routine in an office, you can slowly stop your colleagues from eating all that rubbish in front of you as well!