Check out the work of Dr. Cate Shanahan. Many interviews on YouTube. In short it's to do mainly with the linoleic acid (omega-6) content of those oils, these f

Check out the work of Dr. Cate Shanahan. Many interviews on YouTube. In short it's to do mainly with the linoleic acid (omega-6) content of those oils, these fats are highly unstable / subjected to oxidation. When they get integrated in our own body fat it wreaks havoc. Can't burn fat / inflamed / chronically hungry / tired etc. I don't have a reference but I read a study showing how the fatty acid profile in people's body fat has gradually shifted to more and more polyunsaturated fat. This is not normal and as Dr. Shanahan explains, the integration of seed oil fats in human body fat is unprecedented and a massive experiment for which we're seeing the results for some decades now, but are slow to realize.