Heyhey,
It's always harder to maintain the physique with constant traveling. If you cant prep, then whenever you go to eat outside or something like that, try to always pick the healthiest choices out there. If eating fast food, its so easy to go in calorie surplus since everything is packed with so many sugars and fats, that's why many ppl out there gain fat so fast also, they overeat without even knowing it, cause its easy with such foods.
Your best bet is to prep as much as possible still, if goals are important for you, then you'll figure it out how to do it, get at least some whey or high protein snacks to get daily protein in or get some cleanest stuff out there from some grocery shop. Protein shakes & bars are your best bet, but you can't only eat them, you need some meat and food also. You can always get some premade veggies & potatoes/rice + some decent meat if you're willing to search a bit around the grocery shop.
There must be always something out there that is ready to eat and ain't so bad, or visit some restoran from time to time and pick healthiest thing u can, again there must be something, like clean chicken, veggies & rice etc.
The thing with the fast food is that, some of them can have decent macronutrients, so you can fit them in easily, when you pick the right stuff, but you really lack micronutrients e.g vitamins, minerals etc, which you would get much more from clean and healthy food.
But if you really wanna go with fast food, then make sure to look at the food labels before buying them, if not possible then go to some fast food homepage and you should see each food calories & content there. Just make sure you don't overdo it e.g instead of buying some full meal (soda+burger+fries), try to take burger with just chicken/beef and some veggies + water and maybe throw some protein shake in after meal with water to get the recommended daily amount and feel more full rather than eating all the fast food. Some of the chickens are overfilled with oil, overly fried etc which adds a lot of fat again try to pick the one that has good protein/fat ratio, again try to pick the cleanest and best stuff out there.
Edit: Search up "hodgetwins" on the youtube, one of the best fitness channels out there. Every kcal is calculated, everything, and its not hard at all if you once learn it. They eat a lot of fast food, but the thing is, they know when to stop with it.
Eating fast food and losing weight, its mostly all about calories in -> calories out.
Always look at the food label before buying if you go with fast food, so you know how many kcals & protein, carbs and fats you eat with every bite and how much you need daily. It gets much easier later on when you have learned it and you know what to prefer to eat and what not to, and even if you eat junk, you know when to stop.
Goodluck!
