Yeah. Once or twice a month is what you'd want to aim for... for the average person.
Of course the real issue with nutrtion is that everyone is different and everyone has different body chemistries.
Really, your body will tell you the right amount to eat of anything... if you listen to it.
This is stuff pretty much EVERBODY already knows. He just wanted to harp on a point, make a movie that'd make him some money and set his girlfriend up for a cook book.
It'd be like if some healthy guy who runs marathons decided to smoke cigarrettes for a month and to stop running to see the health effects. It'd be negative.... very. People know that.
Most people just don't care though.
Or stupid enough not to ask questions when they see things like Supersize Me.
Fast food isn't good for you but it isn't the devil it's made out to be either (well except the ridiculous things like the double down).