The study that made the national headlines was just another questionnaire-based, epidemiological study (at best, they only show that two things happen together--they tell you nothing about cause and effect). The only thing I'd like to add on the subject is that for a year or so, I was a contributor for a major data-collecting company. (A weak moment led me to take pity on a nice lady who was trying to make her quota of sign-ups.)
When she gave me the instructions for filling out the forms, she told me, "if none of the answers fits, just pick one." They sent me $5 for every completed questionnaire. More often than not, the truth was not among the multiple choice answers, and there was seldom even a "not applicable" option. They usually asked me to recall and describe in detail such things as where I ate and how much I spent and what I spent it on in the last week, month, or year. (I'm doing well to remember what I had for breakfast this morning!) I finally became so frustrated that I quit returning the forms. I didn't want anyone making ANY decisions based on my default answers.
I've listed the response from Denise Minger first, in case you don't have time to read them all. (Yes, the study has been Mingered!)
(C) 2012, Judy Barnes Baker,www.carbwars.blogspot.com