Bread and choc won't do you much good. Read the Carol Vorderman detox diet! Eat low GI foods which are high residue and fill you up for longer- take a bag of them with you and graze throughout the day when you get hungry. Things like porridge and banana for breakfast, oat cakes, rice cakes, peanut butter, houmous, honey, nuts, seeds, fruit, also wheat free pasta made into pasta salads in a lunch box. Cereal bars from Holland and Barratt are good- usually the pure fruit ones rather than the added sugar ones. Also rye bread if you like it. Drink lots of green or camomile tea. Not only will this keep your blood sugar ticking over, you will be the healthiest person at work!