I thought it was protein https://www.livescience.com/43839-too-much-protein-help-canc...

Makes sense since excess protein is converted to glucose anyway. So ultimately, too much protein equals too much carbs, plus a bit too much of substances typical of mass farming.

Too much of any macronutrient causes a negative effect.

The amount of "too much" for fat is however greater than for the other two, and for most people it's difficult to overeat willingly with fat.

i'm also unsure how much is too much, but fat does affect insulin sensitivity

the issue would be to reduce fat consumption as much as humanly possible, while taking regular blood sugar measurement, only diabetics do this and it's already late by then.

https://www.ncbi.nlm.nih.gov/pubmed/15297079

The abstract of that study doesn't mention carbs. That's a very important detail. If you're eating a "normal" amount of carbs (like in the vast majority of studies of this type, even "low" can mean 25%), it is true that saturated fat makes it worse. But in other studies it has been shown to be the opposite with a fully ketogenic diet, i.e. when the body can't make glucose from carbs or protein and resorts to fat instead. Insulin _must_ be low for ketosis to happen. Insulin is also triggered by low sodium.

I cannot find a single study showing insuline resistance due to high fat consumption when consuming <5% of calories in carbs and <25% in protein.

it mentions insulin a lot, and you cannot metabolise carbs without it.

During ketosis there's barely any carbs to metabolize anyway. That's why I mention carbs at all: they cause the problem and saturated fat just makes the problem worse. A lot of these studies (esp the ones more than a decade old) show this correlation and makes the mistake to attribute the problem to fat.

Our ancestors only found carbs accompanied by lots of fiber. Fiber causes satiety. Carbs cause insulin secretion, which indirectly converts carbs to fat and puts the body in fat storage mode. Storing fat was an advantage to our ancestors because they couldn't ever store fat all year round. But nowadays 30% of calories in carbs is considered "normal" or even "low", but it's actually absurdly high considering the rest of the diet (low fiber, way too much fructose) and our activity.

The study is not as finished as the title may make it sound. The three major killers don't have one cause, but many.

However I agree in that sugar and carbs are a big factor, and one can go a long way avoiding them.