I think I read somewhere that pretty much if you are overweight or obese, you are leptin resistant. It's one of the reasons why losing weight, especially on the SAD, is so difficult.
Jack Kruse has some info on leptin resistance and how to reset it if you're interested on his blog.
As it relates to omega 3s, though, I'm not entirely sure exactly what you're asking. Do you mean going overboard on crappy fats? I'm positive that's all part of the SAD problem, too--partially hydrogenated oils and trans fatty acids.
There's info about omega 3:omega 6 ratios around the web and on this site, too. Tons of stuff available. Chris Kresser posted about that on his blog.