Same concept, but you got some of the facts wrong. It's about this guy who goes on a 30 day McDonalds Diet. He suprisingly, survived all 30 days. He ate the same amount of burgers, fries etc. that a normal person would eat in 8 YEARS! rent the DVD, though. The extra features has this little thing where he puts various McDonalds burgers and a super size fries in individual glass domes. And after several weeks, the burgers are all rotten and moldy, while - suprise, suprise - the fries are perfectly ok! There's so much F-ing chemicals in the fries, that the bacteria pretty much die!
I was probably thinking of a different study.. because another guy did the same thing and the doctor told him to stop at day 14.