It's so easy to fall into unhealthy habits when you travel. Heavy restaurant meals, little scheduled exercise, strange sleeping arrangements and late nights exploring new towns can lead to feeling rundown.

To keep your immune system in tip-top shape (and to keep from returning home five pounds heavier!), it's important to maintain your at-home healthy habits even when you're on the road. Consider these six tips to do just that:

1. Wash your hands a lot! One of the most important ways to reduce infectious disease transmission is to wash your hands carefully and frequently with soap and water, according to the Centers for Disease Control and Prevention. Hand washing--or using hand-sanitizer gel with alcohol--will help stop common cold germs in their tracks, too.

2. Stay hydrated. Although the World Health Organization says that low humidity on airplanes does not cause internal dehydration, it's still healthier to ask your friendly flight attendant for a cup of ice water instead of caffeine-filled sodas or alcohol. Make sure you have plenty of bottled water in your hotel room and drink it throughout your trip.

3. Pack healthy snacks. In your carry on, bring some apples, dried fruit, protein bars, peanut butter crackers or small tins of nuts, so you won't feel the need to make a purchase at one of those ubiquitous mega-cinnamon roll stands in the airport.

4. Make smart choices at restaurants. If you eat healthy meals at home, there?s no reason why you can?t at restaurants, as well. Skip the bread basket, order lean meats and veggies, and if you must have dessert, propose ordering one for the whole table to share.

5. Work out at your hotel or cruise-ship fitness center. If you have a choice among hotels, find one with cardio equipment, strength-training equipment or a decent-sized pool for lap swimming. Nearly every cruise ship these days has a fitness center or track on an outdoor deck. You've got no excuse! But you could also consider bringing along an exercise band for strength training; doing simple push-ups, squats and lunges in your room; scouring the television listings for a cable yoga class; or taking a jog around your hotel neighborhood. Heck, even a walk on the beach is good for you!

6. Get good shut-eye. This is easier said than done, especially if you want to see and do everything on vacation! But do your best to hit the sack early so you can have loads of energy for your days full of sightseeing.