Comment by Eliezer

Linoleic acid (a particular polyunsaturated fat) is possibly implicated as one of the major villains in skyrocketing obesity rates; eg, correlation between obesity and linoleic acid content in body fat, theories about it being a trigger for an archaic hibernation metabolic shift. (Its use has risen hugely over time, along with obesity, but of course you could say the same thing about global warming and pirates.)