According to a report in the Los Angeles Times, I may have ended my burrito fast in the nick of time.
I read that a student at Harvey Mudd College in Claremont, California was told to eat only beans, rice, and tortillas for a week in order to produce a simulation of the kind of human waste one might expect to find in rural Guatemala. The project was abandoned after the unfortunate pupil became hopelessly constipated.
Fish and chips never tasted better.
(see 15 October disclaimer)