Not everyone can take a vacation from a ketogenic diet. If you need to maintain a certain ketone level for medical reasons, then there is no taking time off from the diet just because you are traveling.
Some national cuisines especially lend themselves to keto (such as French food, which has abundant fatty meat and cheese options), while others are more challenging, but can still be adapted.
Engaging with the local food culture is one of the greatest joys of traveling- but you will likely need some emergency rations to get you through. Here are some ideas:
1) Take protein and fat that is easily measurable without a scale and does not require refrigeration. The best products we have discovered for this purpose are biltong (a delicious, typically near-zero carb beef jerky from South Africa), vacuum packed plastic packets of tuna, and good old coconut oil. The biltong and tuna have grams of protein already listed on their packaging, and a tablespoon is all you need to accurately measure coconut oil. Using only these three foods, you could maintain your needed fat to protein ratios and ketone levels while on the road.
2) Be able to eyeball protein and overestimate fat. A serving of meat about the size of a deck of cards often contains around 25 grams of protein. Most restaurants and bars have shot glasses- ask for one filled with olive oil (or whatever oil is available), since you will know it contains two ounces and approximately 60 grams of fat. This is about a 2:1 ratio for your meal and you can obviously ask for more oil shots- ignore the strange looks! If you have no idea how much protein you’re taking in, your best bet is to apply yourself to taking oil shots throughout your meal.
3) Take your meter and test as frequently as you can without interfering with your activities. If your levels are adequate after eating certain meals out, you will get a better sense of what works.
Being aware of your levels doesn’t have to mean a less enjoyable trip, and will arguably improve it by giving you the energy and mental clarity needed to explore. Besides, there are few conversation starters as effective as being the guy at the bar pounding olive oil shots.