I'm not sure I agree with the suing McDonald's (although I do believe these companies have to be held accountable) - but the fact is that fast food is addictive, and it is not the same food as if you or I were to grill a hamburger for ourselves at home. There are additives in the meat, the bun, the sauce, the sodas, etc that make that food highly addictive and since the caloric load is dense, of course it causes weight gain.
Did any of you see Supersize Me or Fast Food Nation?
My 2 cents.
DS