It can be really easy to eat junk when you are traveling. The junk is RIGHT there. There are big macs, french fries, and chocolate donuts at almost every exit. You don't need to eat them though. You can stay healthy while traveling.
1) Preparation is the key - you NEED to pack snacks!
We usually start long car trips either very early in the morning, around 3 a.m. This way we can drive for a while before we need to feed the kids breakfast. In theory they would fall back asleep after being put in the car but my kids are always so excited to be traveling that they stay awake for hours. When bellies start grumbling we pass out cheese sticks, homemade trail mix, raisins, apples, bananas, and/or nuts (chopped for the little one to avoid a choking incident). This usually holds the kids for awhile.
2) Choose your restaurants carefully.
At some point we usually end up at a restaurant. We can get the kids dressed (remember, they were plucked from their beds still in their jammies), teeth brushed, get out our wiggles, and eat a somewhat healthy meal. We always choose a sit-down restaurant over fast food. A real restaurant usually has a larger menu with more options and are willing to customize a meal. For breakfast, Cracker Barrel is a good choice. They offer a low carb meal that has eggs, bacon, and tomatoes. It oddly comes includes bread too - just leave that alone. Most restaurants serve some sort of salad for lunch or dinner. Just make sure you order meat (chicken, shrimp, steak, etc.) on top of the salad or you will be starving by the time you are back on the highway. If you really must eat fast food choose Chipotle. Here is an excellent post on how to order at Chipotle.
3) Bring bubbles!
Sitting for long amounts of time isn't good for you but is near impossible for little ones. Bring bubbles, balls, and frisbees to use at rest stops. When Hannah was 23 months old I drove (with the help of my mother-in-law) from Colorado Springs to Northern VA. That is 30 hours of driving! We stopped at rest stops along the way so that Hannah could run and chase bubbles. When it rained we stopped at Walmart and let Hannah walk around until her little legs were tired. If there are no other options you can stop at a fast food restaurant with a play area to play for awhile. There is no rule you have to eat there just because you are using the play ground.
How do you stay healthy while traveling?