"The average American today is between fifty and seventy pounds overweight," said Dr. Charles Reardon, author of the study. "That means that a terrorist who hopes to fit in here would have to eat like a pig to do so."
I'm not sure whether this will work against terrorism though; the words "Semtex fatsuit" come to mind. (via Richard)
And Al Qaeda's fattest commander has already been detained: http://www.smh.com.au/articles/2002/06/19/1023864455929.html