Hey. Well eat healthy foods that your body processes easily. Like fruit, whole grains, vegs ect. But fruit should be 3 or less servings a day. I find popcorn with salt on it a really good snack as it has only about 100 calories for 3 cups.Or veg sticks and humps eg carrot sticks, cumcuber,calerely (0 calories) Or heathies has yum chips, rice wheels that are from 60-80 calories and heathly.For food wraps are good 130 caloriesplus ffillings.you can grill wraps with topping and make heathly pizza :)
You should try to get up from your desk for a few minutes every couple hours and walk around, do some stretches, etc. You can do leg lifts in your chair, various arm exercises, etc. Try a google search for "chair exercises".
Here's one I found that has really good work place exercises:
http://www.webmd.com/fitness-exercise/features/exercise-at-your-desk
Here's another one:
http://www.forbes.com/pictures/efkk45efdje/best-exercises-to-do-at-your-desk-2/
Of course, there are certain exercises that you won't want to do when wearing a dress and if wearing high heels, you'll probably want to take them off; also most of those done in a chair, were chairs with wheels, so you'll have to make sure to lock the wheels of your chair if possible, or brace it against a wall, etc so the chair doesn't slip from under you and cause an injury.