I work 12hr shifts and it can be quite hectic so probably burn off quite a bit during the day.
What works for me (other than the 10 miles fast commute each way) is only taking a limited food supply and avoiding the canteen where I can purchase as much food as tempts me!
Rarely have breakfast before the ride unless it is cold and I want something hot before leaving the house when I have porridge or just a coffee. Cereals with milk mid morning, couple of sandwiches and an Apple for lunch then a banana mid afternoon. Sometimes I only take one sandwich instead of two, because if that is all I have then I can't eat any more. I rarely miss the extra sandwich!
The main thing is to keep busy so you don't have time to think about food, and definitely don't snack! We have Klix dispensers at work that dole out choc and crisps if you put credit on your own Klix key. My Klix key was issued to me when I started 9 years ago and is still in the sealed pack it came in, unused
A bit of discipline helps....... and don't take any money to work