You might think that maintaining a healthful diet while vacationing is impossible thanks to all-you-can-eat buffets, poolside bars, and gas station cuisine. But we're here to bust that myth once and for all.

Below, you'll find tips on how to eat healthy while on vacation. Follow this guide to travel nutrition the next time you head out by plane, train, or automobile.

Plan, plan, plan.

If you want to avoid dooming your diet during vacation, you need to plan. 

• Look at menus ahead of time and figure out your meal (and stick to it) before heading to the restaurant. 
• Pack non-perishable, healthful snacks in suitcases, briefcases, purses, and cars. (More on this below.)
• Choose accommodations that have a small kitchen so you can cook healthier meals during your stay. (You'll save money, too!)
• Drink plenty of water.
• Organize activities that don't revolve around food. Think hiking, swimming, tennis, golf, and the like.

Planning also involves mental planning as well. For example, remind yourself of the reasons why you should make healthy choices, such as decreased GI symptoms, weight management, and increased energy.

Not sure how to navigate a menu? Avoiding fried food is going to narrow down your choices to the healthier options right off the bat. No matter where you are, they're going to have some sort of grilled chicken or turkey or vegetarian option. Those will automatically be lower in fat and calories than chicken nuggets, pizza, or fried clam plates.

Pay attention to your side dish selections as well. Choose rice over French fries and onion rings. Another tip: always ask for the vegetable of the day, even if it's not listed on the menu.

Indulge mindfully.

Yes, you can enjoy the occasional treat or indulgence, as long as you go into it mindfully. 

For example, if you've been looking forward to a fried clam plate (and fries!) that you get once a year during your Cape Cod vacation, go for it. Savor and enjoy. Like so many things in life, the key to indulgence is moderation. An occasional indulgence is fine. What you want to avoid is overindulgence. So have that fried clam plate one evening, but focus on more balanced choices throughout the rest of your day—and for your other nighttime meals. 

Another strategy for avoiding overindulgence? Portion control. Buffets can be danger zones for this reason. Skip the buffet altogether and order off a menu whenever possible. But if that's not an option, or you're really looking forward to the buffet, make a mental pact that you'll only make one trip through—and that you'll fill a good portion of your plate with more healthful options, like fruits, veggies, nuts, beans, and whole grains, before adding in that special treat. 

The same is true with salad bars. It's easy to trick ourselves into thinking we're having a healthy meal—it's a salad, after all! But if we pile creamy dressings, croutons, bacon bits, and tons of cheese onto the lettuce and kale, we'll end up consuming many more calories, fats, and salt. 

Speaking of portion control, choose small or kiddie sizes whenever you have the option. Portions are so huge nowadays that the small size will be just fine. This helps satisfy the craving for whatever the treat is without going overboard on portions.

Another good strategy: Don't fall into the "all or nothing" trap. Unless you're dining in a place known for its authentic cuisine (like Italy), then the food choices available to you on vacation are also available to you at home. So you don't need to think, Well, I need to eat this now because this is the only time that I can have it.

Technically, you can have that food whenever you want. And so sometimes if you can just kind of take the power away from that 'I need it now' mentality by reminding yourself that you can have it any time, you might be less likely to overindulge.

Keep in mind that overindulgence has consequences that go beyond our clothes feeling snug. If we eat heavy, processed, and/or fried foods for a week or two, our bodies are going to feel sluggish (and possibly constipated!) when we return to the office. Which defeats the purpose of having that downtime to begin with. 

And if advice like "indulge mindfully" is too vague and you want a more concrete directive, follow the 80/20 rule. If you follow your healthful diet 80 percent of the time, the other 20 percent can be for treats and special occasions.

Always have a stash of healthy, travel-friendly snacks handy.

A favorite go-to snack is nuts (provided you don't have a nut allergy). Nuts are so portable, nutrient-dense, and packed with protein. (Like everything else, be mindful of portions.)

Nuts that come in single-serving pouches make snacking and portion control even easier. And they travel like a breeze. Plus, you can usually find nuts everywhere—from gas stations to convenience stores to airports.

Fruits with thick skins are great options while traveling, too. Think bananas, oranges, and apples. And don't underestimate the value of good Tupperware containers for other types of fruit.

Protein bars are easy to pack and travel well also. Be aware, however, that not all energy bars are created equal. Pay attention to sugar and fat. Three brands to consider: Perfect Bars, RXBARS, and KIND Bars. 

A good snack option that might surprise readers: turkey jerky. RDs don't normally promote processed foods. But you can find low-sodium jerky options that are high in protein. These can also be an option to curb your appetite for a little while. (A low-sodium option to check out: uncured pepperoni turkey sticks from Vermont Smoke & Cure.)

Don't forget the H20.

Hydration matters, especially on planes and during hot summer vacations. Water is certainly very important, and it can be easy for us to not drink as much when we're on vacation, often because we're busy or it's not as practical as when we're home. A lot of times, people complain about getting constipated when they're traveling, and a lack of water can often be the reason. Always bring your water bottle with you. 

What should your daily fluid intake be? Here's a good rule of thumb. Divide your weight (in pounds) by two. The resulting number is the recommended fluid intake (in ounces) from all sources—your daily coffee, fruit, soups, etc., not just water.

When it comes to other beverages during vacation, stick with water as much as possible. Or if you must have something else, choose sparkling water and unsweetened iced tea or coffee (rather than sugary sodas or sugar-filled frozen drinks that tend to be staples of most convenient stores.)

Watch your alcohol intake.

If you drink more alcohol during vacation, you may be in for a double-whammy in terms of consequences. Sure, alcohol like beer and wine can increase the calorie load. But vacation time is famous for signature cocktails that can often have added sugar and creams. (Think frozen mudslides and daiquiris, for example.) 

Not to mention, drinking alcohol often affects our good judgment when it comes to what we eat. Suddenly that appetizer of loaded nachos sounds perfect!

Monitoring how much you're drinking is important because the more alcohol we drink, the more we tend to make unhealthy food choices. So then not only will you be drinking more calories from alcohol, you'll also be eating more calories via food. A good approach: Aim to have a glass of water in between each alcoholic beverage.

Be kind to yourself.

If you fall off the healthy-eating wagon for a week, don't beat yourself up. You can't change what happened last week, but you can focus on getting back on track this week. Drink plenty of water, get plenty of sleep, and focus on choosing healthier options as you move forward. You got this!