You need to establish strict principles about meals (and not only meals) at the work, if you do it, you will achieve your goal. I know some people, who don't smoke during the work shift for certain reasons, and they've been successful at it.
But you need to respect some rules and after the work, don't seek a lot of meals after work, especially on evening time.
That's not an easy task :) especially if you are 24/7 are surrounded by the food you like... But if you really want to loose weight - then no doubts - only strict diet and take allowed food (like salads and fruits with you, to have something allowed to eat).