Two years ago when I started heavy travel for my job, I put on a few pounds. It was too easy to pick up fried foods, ice cremes, and calorie filled flavored coffee drinks. I discovered a book written by Peter Greenberg that tells you how to eat better, exercise more, and have a good time traveling.
I quickly learned and went to the restaurants that Mr. Greenberg wrote about. When I flew American via Chicago there was a great Portobello Mushroom Sandwhich. When I would fly United there is a small frozen yogurt stand in Terminal C. I would look for Subway, have a McDonalds Sandwich, or go without cheese at Quiznos.
If there was ever a delay (I know, right) I would walk around the terminal. Several times in Minneapolis, Detroit, or Chicago I would visit every gate possible and got a decent walk out of the deal. It was a great way to pass the time.
You can pick up Peter Greenburg's book The Travelers Diet at any bookstore.
Plus, there is a new article from MSNBC about how to travel healthy.
How to find healthy airport food
Peter Greenberg Worldwide