Walk up stairs, don't take the elevator. After all 5 minutes of high intensity training is better than an hour of low intensity training.
Cook your own meals. Restaurants survive because people love the taste of butter. If you've never worked in a restaurant or don't know a chef, ask about it. Butter makes everything better, except your waistline.
Move to Europe and don't buy a car. Just having to get around is more exercise than most Americans get.
Well, at least the first two are easy.
Read "The Zone". The first one, not the cheesy simple dumbed down later versions. Its the most accurate explanation of how the body deals with food in popular literature that I've come across. (I have a strong biology / endocrinology background, oddly enough) Follow its tips on how to eat and you will see improvements. Don't worry about following it to the letter. Focus on learning major concepts, like what is "glycemic index".
I take regular breaks from the computer and jump rope, jog in the park across the street, or some other quick 15 minute activity. Not only does it make your mind work better, keeps you healthy. Try it!
Wellington commented about laws going into place about food, while commendable given the epidemic of obesity in the States, I really don't see this as being the role of government. Education perhaps, and parents teaching better eating habits...