This idea is my final fat loss "enlightenment" that has made everything come together and make sense.
Imagine you are wandering around the wild, hunting and gathering. Or, more appropriately, the men have gone out hunting, and then women are gathering.
What foods are the women eating and finding mostly?
Berries, tubers maybe, nuts, seeds, herbs, and perhaps some greens
What are these foods made of? Carbs mostly
If you find nuts/seeds? Fat mostly
Each food has a primary macronutrient profile. It does not have carbs + fat + or protein in high quantities.
Now imagine you are hunting big game. You take down a bull or elk or venison.
What macros do you find? Fat and protein and zero carbs.
Now think hard in the wild nature. Find me food with carbs, fat, and protein from one food source.
When I started thinking about this idea, I was blown away. You need help finding it.
Most foods are carbs, fat, or fat and protein.
So the only time we can eat carbs, fat, and protein together is when we have an industrialized food system and bring these foods together.
Our ancestors weren't professional chefs. So they tended to eat single foods at a time. Maybe we had some fruit or tubers we could bring back and eat with a fresh kill. That happened sometimes, I'm sure, and it would have been a survival advantage if we could make it happen.
But much of the time, I envision us eating just tubers or fruit, animal fat and protein, and those being separately more often than not.
And this is why eating carbs and fat together is the most dangerous mix for modern humans: because it results in fat gain that is what we don't want today. In hunter-gatherer times, we def wanted fat gain. So we would have loved to eat carbs and fat and protein altogether. Today we don't want that. Our environments are mismatched.