IMO, only those truly anal people follow those kinds of plans by the letter and encountering them in person scares me. I saw a guy at a McDonald's who was obsessing over the nutrition facts that were posted on his cheeseburger wrapper, scribbling them into a notepad and punching numbers on his calculator. One of the most extreme examples of this, if I ever saw one. This isn't normal behavior, or human at that.
I don't really log what I eat. I just cook and eat whatever is available, or whatever I feel like eating. I do the grocery shopping for the most part and sometimes I don't eat that third meal in a day. To me, it's enough to play it safe by eating a few fruits/vegetables and protein daily and that's about it.
Heheh, if you're classifying as slightly underweight I'd say eat more in a friendly way, of course.