Yes, it is true. If you feed your slaves the only food that is cheap, easy to produce and accessible then those slaves will die of clogged arteries.
After they have had a useful and productive life as slaves, of course. Slavery is not about retirement. It is about slavery.
Mummies found mysteriously wrapped in caramel bacon, cheesewhip and butter-fried marshmallows. Scientists puzzled to deduce what killed them. Carb-eating bastards. It's called the diet of Cain and it will turn your insulin into a system-wide grease-plug.