Garbage or dog food?

From an article on obesity in the National Post:

Children or teens would have to submit to psychological testing to rule out other factors, such as drug abuse, an underlying psychosis or a medical condition such as Prader-Willi syndrome, a baffling genetic disorder that causes such extreme hunger and over-eating, children have been known to eat garbage and even dog food.

That's kind of curious language. Am I to take this to mean that dog food is worse than garbage? If so, this gives added punch to the phrase "not fit for a dog." And if dog food is so horrible, why would we subject our pets to it? Even if you don't care about being humane, you have to admit it would at least be cheaper to feed your dogs garbage instead.