I've checked the book I recommended in the comment. It is written by a PhD Robert K. Cooper and is entitled "Flip the switch".
A simplification of what you could read there is as follows:
We have limited storage space for excess protein, and the amino acids from them remain in the bloodstream for only about 4 hours. thats a good reason to include proteins in every meal and to keep the amounts reasonable.
The author claims that the body may slow the metabolism when low on proteins, while an optimal amount of them can boost oxygen consumtion by 200-300%, indicating a higher metabolic rate. He points out that protein rich meals produce a greater and longer lasting sense of fulness than high-fat meals, as proteins break down slower than fat and carbs. He discusses the quality and sources of protein.
As for the timing of the meal. Obviously, you will be low on pretty much everything after 7h of sleep, so you shouldn't wait very long with your first meal of the day. In the books terminology, bright light exposure, calm but energetic action, small, high protein meal and some physical activity within 30min after the meal are all "switches" that help boost your metabolism. Citing thereasoning behind it would be actually too much work, but you can read the book itself.
If you check the bibliography for the chapter you'll see, among others, these papers:
- Studies by Callaway, W. Cited in Rodin, J. Body Traps
- International Journal of Obesity 28(2004)
- Leveille, T. "Adipose Tissue Metabolism: Influence of Eating and Diet Composition" Federation Proceedings 29(1970)
He quotes some studies etc. Anyhow, even tho I'm not sure all the contents of the book are 100% truth, and there may be some mistakes, it's still a worthy read, especially if you dont want to dig in to all the science behind it. If youre insisting on knowing the reason "why", I'm afraid you have to mail the author of the book you read or start educating yourself on nutrition, cause even the specialists don't seem to agree on the details ;)