Yes, they clearly mean that it doesn't work at a societal level. If you take a human and force them to exercise more and eat less, they're going to lose weight.

Yes, they clearly mean that it doesn't work at a societal level. If you take a human and force them to exercise more and eat less, they're going to lose weight. And everyone knows that, but pretty much every modern society is increasingly overweight. Ergo, "it doesn't work".