Why does iodine react with the molecules in certain oils e.g; olive oil, peanut oil, soya oil & sunflower oil?

Iodine reacts with some oils because they have some double bonds in the molecules.


I would think the reaction is electrophillic addition because of the negative region in the oil.


I'm hoping these particular oils are quite thick and gloopy, otherwise it would be more likely that they are fats!