Ancel Keys postulated that saturated fat was the main driver of increased cholesterol and heart disease, while John Yudkin believed sugar was the primary driver.

“the that debate was hardly even a debate basically Ancel Keys won the battle there's a very famous time cover that shows ansel key is in the heart and that solidified the what's known as the lipid hypothesis and at that time they were looking just at total cholesterol predominantly but what helped to make it very intuitive is that when you when you cut open are is that have been clogged you find that indeed there is cholesterol in those arteries things that they call fatty streaks which is basically the first visible sign that there actually is after us grossest and throws grossest being the build-up of plaque in the arteries and because of that it seemed pretty obvious that well actually and I should say this ansel kids was first saying just unadjusted cholesterol eventually that morphed into saturated fat in particular seems to increase cholesterol in the blood but regardless whatever brought in more cholesterol in the blood was likely a culprit from their perspective as to why it is that you would die more from heart disease”