Jane that's a tough one. Sounds as if you need to be super-organised and plan how you're going to fit some healthy food in each day. Can you take sandwiches, or a pasta salad or something to snack on when you're busy?
I've got into the habit of taking an apple plus a little tub of strawberries, grapes or blueberries to work. I have them for my "afternoon tea" when everyone else is eating biscuits and chocolate.
Also, check out the porridge thread (if you can find it) - a good helping before you go to work will keep you going for ages without feeling hungry. Good luck!
