I have not touched on the challenges of travel and living in hotels, which I do quite a bit. As long as I have a small refrigerator and access to at least a convenience store, it has not been a problem. I also carry a small store in my backpack, now (various nuts, protein bars, and low-salt chicken jerky). Those portable packets of tuna, along with the jerky, are perfect travelling protein, when you are not cooking; do not forget the plastic utensils.
My opinion is that what I am recommending involves putting the control on you rather than turning it over to some external thing: your endless computer and phone apps, your fitbit recorder, your Atkins Diet, your Weight-Watcher program, your standing desk. All of these things are great, but why ignore the fundamentally simple idea of looking at the input of food into your body, which is a thing you have total control over. And even if it is not actually controlled, monitoring it to know, if only to you in complete privacy, is worth knowing.
Maintaining and manipulating a detailed spreadsheet is also probably not for everyone, either, but I am figuring that if you are still reading this, you can handle it. Someone other than me can try to develop the way to automate it, but I have a sneaky suspicion that automation leads to externalization of control. In a critical way, I think that having to pound the numbers and think about every detail are actually critical to the psychology of this approach. I also love to cook, and invent and adapt meals. If a person did not like to cook, or had to deal with feeding a family, this would all be much more challenging (not the recording, mind you, but the changes).
I knew calories. I knew labels. I knew portions. I had a good idea of what to avoid. But I did not figure it out until I really had to, and when I put all of the pieces into one place. And (frankly) I was shocked at just how easily a normal trip to the grocery store adds up in an unbalanced way. I think there are entire aisles from the grocery store that I will not eat from any more, even when I move my calorie count up to a weight maintenance level.