Polyunsaturated fats are more susceptible to oxidation both in external environments and within the body compared to monounsaturated and saturated fats, due to the presence of multiple double bonds in their chemical structure, which increases the potential for oxidative damage.

Study: The energy savings-oxidative cost trade-off for migratory birds during endurance flight

The study shows that birds burning more polyunsaturated fats had more oxidative damage, which supports the idea that these fats are less stable and more likely to cause damage when used for energy.

Study: The Influence of Dietary Fat Source on Life Span in Calorie Restricted Mice.

The study found that mice on a low-polyunsaturated fat diet lived longer, which makes sense because these fats can go 'rancid' more easily in the body, causing damage.

Study: PUFA-dependent alteration of oxidative parameters of a canine mastocytoma cell line.

The study shows that when cells are given polyunsaturated fats, they produce more harmful molecules linked to damage, which supports the idea that these fats are more likely to oxidize and cause harm in the body.