It was Barry Sears in a Zone Diet book. In his first book, he advocated a diet whose calories consisted of 30% lean protein, 40% complex carbohydrates, and 30% healthful fats (for each meal, not just overall). In a later book, he said, basically, "Oh, everybody's not the same! Start with that and then adjust it as follows". I just checked the Wikipedia entry and it gives the original figures, not the how to adjust it. I'm somebody who does very very well with that ratio of protein to carbohydrates. I know other people who do very well eating a significantly higher % of carbohydrates and who don't seem to have any need to do the "balance each meal" thing.