Amps Read a thing this week about how mind bendingly deadly vegetable oil is. In terms of death rate / life span, having fast food that has been deep fried is the equivalent of smoking 20 fags.
But the important bit for you @-si- is the fact that veg oil is an inflammatory and will massively fuck over your joints. So switch to plain butter and swerve the fast food or anything else that will have been cooked in veg oil of any sort. Trickier than it sounds.
So my request for Amps to “show his source” for this was justified, given that as per he’s likely misrepresented whatever material he’s reading from and missed any nuance.
Obviously in general food which is deep fried is likely to be unhealthy and should be avoided.
However, the extent of the potential negative health effects from fried food greatly depends on: the specific type of oil used; the temperature of the oil; and how long the oil was heated for.
Also, your comment “swerve […] anything else that will have been cooked in veg oil of any sort” is misleading - it’s true that any blend or generically labelled “vegetable oil” should be avoided, and most individual types of vegetable oil should also be avoided, but there are a few individual types of veg oils which can be fine, i.e. canola/rapeseed oil, safflower oil (not sun), and flaxseed oil.
Two of the main things which you need to consider based on the issues you’re referencing when picking your oil are:
%age of the oil which is Omega 6 fatty acids (linoleic acid), as it increases the toxicity of the oil when fried (linoleic acid when fried increasingly releases toxic aldehydes with more time and heat). The cigarettes article you (Amps) read was likely referring to the production of these aldehydes.
ratio of Omega 6 to Omega 3 fatty acids in the oil. The aforementioned Omega 6 fatty acids are generally considered inflammatory and so should be avoided in high quantities (though there is still some debate about the extent to which they are actually inflammatory, see ‘insider’ article below). Meanwhile, Omega 3 fatty acids are generally anti-inflammatory. Generally a balanced ratio of the two is recommended for a healthy diet, but if you’re @-si- and worried about inflammation then you should perhaps encourage your Omega 3s a bit more, including maybe supplements.
(P.S. I won’t get in to the separate saturated vs unsaturated fats issue here as it’s even more nuanced and personal, and less clear-cut.)
Here are some easy summary charts to illustrate which oils to pick based on the above points.
Firstly, avoid the oils in the below chart with the high blue (Omega 6) percentages, e.g. sunflower oil, corn oil, soybean oil and cottonseed oil); and if said item is deep fried then avoid like the plague:

This chart has a few more types of oils (again, regardless of the saturated vs unsaturated issue, you want to avoid the high Omega 6, this time purple). The chart has an added Omega 6 : Omega 3 ratio on the right-hand side.
- Oils such as flaxseed and salmon (generally fish) oils are higher in anti-inflammatory Omega 3s (and have ratio numbers less than 1). (Worth pointing out you can’t cook/fry with flaxseed oil though due to its low smoke point; it can be used in say salad dressings though)
- Canola oil is relatively balanced while being marginally higher in Omega 6 (and has a lowish 2.2 O6 : O3 ratio).
- As a side-note, if you were to just look at the olive oil O6 : O3 ratio it’d be a bit misleading as although it’s a fairly high number you’ll also see it has hardly any O6 anyway. Plus it also contains a lot of antioxidants which are considered anti-inflammatory.

Finally, this graph illustrates how significant a differential effect the type of oil and the length of time frying has in creating damaging aldehydes (2,4-decadienal is a type of aldehyde).
The “vegetable shortening” oil was specifically a blend of sunflower, cottonseed, and palm oil (the first 2 of which are high Omega 6).
The ’Frying Batch" is the numbered batch of fries cooked in the same continuously heated vat of oil.

https://www.healthline.com/nutrition/optimize-omega-6-omega-3-ratio#TOC_TITLE_HDR_5
https://www.gbhealthwatch.com/Science-Omega3-Omega6.php
https://www.ift.org/news-and-publications/food-technology-magazine/issues/2018/may/features/do-cooking-oils-present-a-health-risk
https://www.insider.com/seed-oils-arent-worse-than-cigarettes-despite-keto-claim-2020-7