I don't think you can really dismiss macro-nutrient allocation as a factor. The metabolic pathways for fats and carbohydrates are just way different. For some reason people think that this stuff works like a gas tank, where all that matters is how much fuel you pour in, but the evidence clearly shows that what kind of fuel you pour in is incredibly important.

If you think about how incredibly complicated things like nutrients and proteins are, and how insanely complicated the body is, it makes sense. We've evolved so that we can eat almost anything, but that doesn't mean that we should eat anything. The evidence seems to point towards carbohydrates being something that should be eaten when there's a large energy demand and otherwise should be kept low.