The BRAT diet is Bananas, Rice, Apples and Toast.
Some sites like this first one add Yogurt.
http://www.mademan.com/mm/5-foods-stop-diarrhea.html
In this wikiHow, the A is applesauce and the Bananas should be green:
http://www.wikihow.com/Treat-Diarrhea-(BRAT-Diet-Method)
Wikipedia has the applesauce but doesn't specify green bananas.
http://en.wikipedia.org/wiki/BRAT_diet
About has BRAT, also adds yogurt, chicken, and blueberries.
http://ibs.about.com/od/diarrhea/tp/Diarrhea-and-Food.--04.htm
One site will say "Don't eat fiber." and yet the bananas are also explained as having fiber. Similar issues occur with sugars. So there doesn't seem to be a consistent approach.
Is the BRAT diet backed by any kind of scientific studies or evidence or is it more of a folk remedy passed down by word of mouth?