Without access to your local supermarket or your favorite Pilates DVD, on your next trip you may find yourself subsisting on greasy fast food and abandoning your usual exercise routine to sit for long hours on planes or buses. Vegetarian, organic, low carb, low cal, low fat -- no matter what diet you're on, there's a good chance that it went down the tubes on your last vacation.

But believe it or not, it is possible to eat well on a cross-country road trip, to stay active without access to a gym and even to go on a cruise without gaining 5 or 10 pounds. You can eat healthy and stay active no matter what kind of trip you're taking.

On the Plane
There's no more captive audience than a plane full of air travelers, particularly those on long international flights. But just because you're stuck on a plane doesn't mean you're stuck eating the congealed meat and starchy sides the airlines call food. (That's if your airline serves meals at all.)

Your first line of defense against unhealthy airline menus is to bring what food you can from home. Airport security rules prohibit passengers from taking liquids and gels in excess of 3.4 ounces through airport security checkpoints, but solid snacks like bananas, apples, trail mix, nuts, carrots, celery sticks and energy bars should pass muster. Pack a few of these in your carry-on and skip the airline's salty snacks.

Once you've passed through security, anything you buy at the airport may be brought onto your flight, so this is your chance to stock up on bottled water and buy a salad or sandwich to eat on the plane. Many airports have begun adding more healthy dining options to their standard array of fast food; look for dishes with lots of vegetables and fiber, and skip the fried stuff.

In flight, avoid alcohol and soft drinks -- both can dehydrate you. Water is always your best bet for staying hydrated and sticking to your diet.

Healthiest Airport Food (and Airport Food to Avoid)

On the Road
Long hours of sitting in the car and eating fast food at every rest stop can derail a diet faster than you can say "road trip." How can you break the cycle? First, take McDonald's off the menu. Before you set forth on your journey, fill a cooler with healthy snacks like fruit, raw veggies and sandwiches from home, and then restock your stash along the way with offerings from local grocery stores. Don't forget the bottled water! (Save money and the environment by purchasing gallon jugs of water to use to refill your bottles.)

Bypass rest stops and seek out independent cafes and restaurants -- not only will you eat better, but you'll also meet locals and get a better flavor of the town you're in. For help finding healthy local eateries, try the VegOut app, which offers listings of nearby vegan, vegetarian and vegetarian-friendly restaurants. GoodFoodNearYou is another useful app that pinpoints the healthiest menu options at restaurants in your area, including fast food chains. You can also use our Rest Stop Survival Guide to choose the healthiest options from popular fast food menus.

On particularly long car trips, be sure to stop at least once a day for an exercise break. Check your road map or GPS for nearby national, state or local parks where you can go for a hike, or spend some time exploring a new town or city by foot.

The Eight Best U.S. Road Trips

At the Hotel
When choosing a hotel, look for one that offers a fitness center or pool -- and then use it once you get there! Many major booking sites, including Travelocity and Orbitz, allow you to customize your search to show only hotels that offer certain fitness amenities.

If your hotel doesn't have a gym, why not bring your own? We don't advise trying to squeeze a set of dumbbells into your suitcase, but it's easy enough to pack a resistance band or to download an exercise program onto your MP3 player so that you can work out in your room. (iTRAIN is one of several companies providing downloadable workouts.) As a lower-tech option, you can always jog around the local neighborhood, make your own exercise routine of jumping jacks and squats, or do some early-morning stretches or stomach crunches before heading out for the day.

You may also want to consider booking a hotel room with a kitchenette or even renting a house or apartment so that you can do your own cooking. This will save you money on food and give you more control over your diet. If you choose to eat at the hotel instead, be sure to take a careful look at what kind of dining options are available. Several hotel chains have eliminated trans fats from their menus in the past few years, including Loews and Omni.