There's a growing movement claiming saturated fats(coconut, palm, animal) are not as bad as once thought and that high levels of polyunsaturated fatty acid(like Omega-6) found in seed oils(canola, soybean, sunflower, etc) are very bad. Hopefully we can get more research into this.
Any kind of food can be harmful when eaten in excess, even when it is required for surviving, but in smaller quantities.
Oils with high content of linoleic acid (omega-6), like cold-pressed sunflower oil (which is also very rich in vitamin E) are very healthy in smaller quantities, e.g. 15 to 20 milliliter per day, but they can become harmful in too large quantities, e.g. more than 50 milliliter per day.
For instance, a combination of 50 milliliter per day of EV olive oil with 20 milliliter per day of cold-pressed sunflower oil gives a fatty acid profile that is close to optimal, according to the current knowledge.
Eating only olive oil would require a much greater quantity of oil for providing enough linoleic acid and vitamin E, which would provide too many calories for a sedentary lifestyle.
Eating only sunflower oil in an amount enough to provide an adequate fraction of the daily calories would provide too much linoleic acid.
So only a mixture can satisfy all criteria.
With saturated fats, the effects are similar, in smaller quantities they are healthy, but in large quantities they can be harmful. Olive oil, avocado oil and various kinds of nuts, e.g. almonds, hazelnuts, cashew, pistachio and a few others have a good balance between oleic acid and saturated fats.
There's a growing movement claiming saturated fats(coconut, palm, animal) are not as bad as once thought and that high levels of polyunsaturated fatty acid(like Omega-6) found in seed oils(canola, soybean, sunflower, etc) are very bad. Hopefully we can get more research into this.