Try a protein shake about an hour before you work out, then have a proper lunch with salad or vegetables around 13.00 , and a small protein based snack before you go to work. Take a proper break even if it has to be at your desk. You will be more productive. Make it something lowish carb or you will be drowsy ... Maybe some chicken, with veggie sticks, and a few wholewheat crackers, and have a snack box with fruit, nuts, maybe a cereal bar, in case you find your energy drops. If you are hungry when you get home try a banana, or maybe a single weetabix, when I did strange shifts switching to smaller snack meals kept my energy and alertness levels higher than trying to fit in normal meals.