I read in a book that in a prison in bangkok (think the book was called "The Damage Done")
But they were given dirty rice to eat and that was it....so some of the guys who had been in there for a while showed the main person what they did with the rice...

They lifted up the floorboard and there were apparently massive roaches under there.....they fed their rice to the roaches to fatten them up....and they had managed to get some salt and oil.....then when the roaches were fat enough they would crush them up into a paste with some oil and salt and eat that instead of the rice....

I thought that was pretty disgusting.....