I met YC when I was living in Japan. He is from China, and makes delicious gyoza. But, since I only eat halal meat, I don't eat the gyoza he made.
To YC, my food restriction practice is "mendokusai". Mendokusai is the Japanese word for "troublesome". His opinion didn't come as a surprise, even expected actually - at one time he told me of the Chinese saying - "anything under the sun that can be cooked, can be eaten"...
Anyway, regardless of his sentiments towards my dietary practice, YC at one point began making two kinds of gyoza - one with meat, and the other filled with scrambled eggs (just for me). What a sweet heart!
Practicing food restrictions, for whatever reasons (e.g. religion, medical, belief, principle) while in a foreign country, would appear to those uninitiated or unfamiliar to it as mendokusai or even challenging. I suppose that was how YC looked at me - a Muslim who eat only halal food, living in Japan, where Muslims make up a very small minority.
I come from Malaysia, and I am used to easy access to halal foods in my country - halal foods is available everywhere and clearly flagged by the halal logo. Thus, to some extent, I do agree that practicing food restrictions in a foreign land is not easy. But I won't go so far as to regard it as challenging. You just need to put in a little bit more effort to find what you can eat, that's all.
Here are some things I learnt on my travels (mostly while eating chocolates)...
There are many variations of the vegetarian symbols on food packages. Specifically, in my travels to India, I got acquainted to the green dot - the vegetarian symbol applied in India. It became the best friend that I would refer to when buying food items at the hypermarkets.
The green dot on a food package indicates that its ingredients are plant-based and can be eaten by a person who practices vegetarianism. One thing to note is that milk and dairy products are also marked with the green dot. The other important symbol is the brown dot. It indicates that the food item is non-vegetarian in nature.
While Muslims eat halal foods, Jews eat kosher foods. Food that is kosher is flagged with the K symbol (note that there are other variations of the kosher symbol).
Without going too much into the theological aspects, it is suffice to say that Muslims can consume kosher foods as a substitute to halal foods since the kosher rules (especially with regards to the animals of which meat can be eaten and how they are prepared) is very much aligned to the halal rules, if not stricter.
So, food restriction practice is mendokusai? Not really, methinks...