You have to eat foods high in nutrients. A calorie is not a calorie. In other words you have to eat foods that are dense in essential nutrients; you can eat less of these foods than say some sort of empty calorie food.
Make a list of food that you like to eat that is high quality in the protein/carb/fat area and stick to those foods. Make sure you get your phytonutrients in as well. Fish/Chicken/leanbeef/broccoli/spinach/olive oil/almond butter/Ezekiel bread/bananas/brown rice/wild rice/
Also I would not recommend eating just 2 times per day as when you get hungry you tend to 'binge' which obviously is not a good thing. Drink plenty of water in between meals and keep some almonds in your desk drawer and an apple each day for small break food.