Fried food kills^Wincreases the systemic inflammation and chances to get atherosclerosis and probably other chronic diseases. The mechanisms are: Malliard reaction/advanced glycation end-products; accumulating in CNS and inducing inflammation: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4496742/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6251169/ 10.1007/s00726-010-0776-z https://en.wikipedia.org/wiki/Advanced_glycation_end-product Lipid peroxidation; those bind to proteins/lipids/DNAs and play a role in disease, but it's unclear whether the dietary peroxides are big enough factor for otherwise healthy humans, as the body plenty of mechanisms for dealing with them. Those with existing chronic conditions demonstrate elevated inflammation markers in response to dietary lipid peroxides: 10.1007/s11746-017-2958-2 https://en.wikipedia.org/wiki/Lipid_peroxidation Surprisingly, trans-isomerization of fatty acids is minor even at the extreme conditions observed during deep-frying. Unless you repeatedly use the same oil, of course, as might be seen in fast food chains and other popular mass production of fried foods: https://pubmed.ncbi.nlm.nih.gov/22668846/