Eat like you normally do.
You might be on vacation, but you still don’t want to come home with an extra five pounds under your belt. You can (and should) eat the delicious foods that your vacation destination is famous for, but don’t overindulge in them. Some easy ways to prevent yourself from doing this at a restaurant include sharing a dish with someone else, ordering an appetizer as a meal, or guaranteeing leftovers by limiting yourself to eating half of your meal. Some restaurants will even pre-emptively let you doggy-bag half of your meal before it arrives at your table.
Enjoy the food and the environment.
Science has shown that slower eaters tend to consume less food because it takes about twenty minutes for your brain to register feelings of fullness. So take your time eating a large margherita pizza in Florence, and soak in the wonders of the city around you. You may find yourself full before you finish the meal, then you’ll save yourself money and calories by having leftovers for lunch the next day.
Sightseeing usually requires a higher than normal amount of walking, so even if you eat unhealthy foods on your vacation, you can usually walk off a lot of the calories throughout your day. There’s an even bigger bonus if you’re in a foreign country without your own car to drive. Resist the urge to take a taxi everywhere, and, if your destination isn’t too far, skip the metro as well.
Balance it out.
There’s nothing wrong with enjoying beignets for breakfast in New Orleans or clam chowder in New England, but those foods still don’t have to ruin your eating plan. The key is balancing out your meals so you aren’t eating what would be ‘cheat meals’ for every meal. Want to have an unhealthy breakfast? Go for it, but then eat a healthy lunch, like a grilled chicken salad or a turkey sandwich.
Pack travel meals and snacks.
The actual traveling portion of your trip is usually the most difficult when it comes to eating well. Airplane food is infamous for being not only unhealthy but pretty flavorless as well. And it’s tempting to just stop at Taco Bell for dinner on road trips because it’s easy and cheap. Packing your own nutritious meals and snacks will save you money and calories, so bring along some trail mix, veggie sticks and low-fat ranch dressing, and lettuce wraps for tasty food on the go.
Some people make the mistake of skipping meals to save calories on vacation, but this rarely works since you’re then more likely to overindulge the next time you eat. Instead, eat a small, low-calorie lunch and some nuts or dried fruit every 2-3 hours between meals. These small snacks are easy to pack in your purse or backpack, so you can chow down at the beach, park, or wherever you happen to be when hunger strikes. Then you won’t be ravenous by dinnertime and will be less tempted to eat the entire bread basket yourself.
Make healthy substitutions.
if you really want a delicious, greasy cheeseburger from the famous Bachi Burger in Las Vegas, don’t deprive yourself, but do consider swapping the fries it comes with for something else, like celery sticks or a salad. You can still steal a few fries from your companions, but you’ll save a lot of calories by skipping your whole share of fries.
The burger is probably the main thing you’re craving anyways, so you can still eat that cheesy, beefy goodness and feel less guilt about it. If you’re really bold, you can also ask them to trade your bun for some lettuce and have a tasty, low-carb dinner.
Limit your cocktails.
Sugary cocktails are laden with empty calories that will add up pretty quickly if you don’t watch yourself. All of these fancy cocktails will probably cost you a hefty amount of cash too, so there are two good reasons to stop after one or two drinks. However, if you really want to have a fun, carefree night out, opt for dry or semi-dry wine or light beer as your drink of choice for the night.
Between hopping on and off public transportation and strolling through cities, you’re bound to get thirsty. It can be a pain to carry around a water bottle, but you should carry a disposable one with you anyways. Even if you have to pitch it to enter a museum, buy another one as soon as you leave. Being hydrated is essential for maintaining your health for many reasons, and one of those reasons is that your brain can misinterpret signals of thirst as hunger. In that situation you're more likely to go ahead and eat something when your body actually needs water.
Maintain a normal sleep schedule.
If you’ll be doing a lot of sightseeing on your trip then you’ll probably be waking up early in the morning to get going. If this is the case (and even if it’s not), resist the urge to stay out and bar hop all night long. Studies have shown that even a single night of poor quality/not enough sleep drastically increases hunger hormones, which can make high-calorie foods more tempting as soon as you roll out of bed.