[andor]

"Vegetable oils require an industrial process of extraction - with high temperatures and hexane"

You're talking about refined oils. This method of extraction has a higher yield and is therefore less expensive. It also increases the smoke point of the oil, making it more suitable for high-temperature frying and deep frying.

While I don't know what's available to consumers where you live, solvents and other chemical treatment are not required for vegetable oil production. Seeds can be cold extracted. The result is much more expensive though.

"the output is novel to humans on evolutionary scale"

This is true for all oils and all other highly processed foods.

"they come from inedible waste which for millions of years has been discarded - seeds etc"

Seeds are not waste. Do you think bread is made from waste?

The notion of using "waste" comes from the production of refined oils. The seeds are initially pressed, resulting in oil and meal as the byproduct. The meal still contains some oil which is extracted with solvents. After the solvent treatment, the meal is used as animal food.

[m0llusk]

There is a detailed four article series about this which was recently shared here on Hacker News. The first article is here: https://www.jeffnobbs.com/posts/what-causes-chronic-disease , but the second and third articles probably address this most directly.

>> "the output is novel to humans on evolutionary scale" > > This is true for all oils and all other highly processed foods.

That is not true. There is evidence that humans have sought out fats and oils for most of our history. Lard and other rendered fats are made from heating animal fats directly with modest heat being sufficient to liquify animal fats. Butter is made from churning milk. Olive oil and Coconut oil are made by squeezing fruits. All of that is quite different from modern vegetable oil processing which requires high temperatures which in turn convert a fraction of the oil into transfats. When oils refined in these ways are then used for cooking they become increasingly dangerous as they are heated.

[imtringued]

And when food is deep fried, the oil is often being reused and reheated repeatedly until it is no longer fit for human consumption at all.

This has then lead to the popular misconception that fat inherently makes you fat.