‘John was clothed with camel's hair, and with a girdle of a skin about his loins;’ – he seemed like Elijah – ‘and he did eat locusts and wild honey.’ Mark doesn't say that he only ate these things, but he lived out in the wilderness, and he lived very simply, and his life was a rebuke to the people.
Our lifestyle must be consistent with our message, otherwise our lives undermine and weaken our message. A person whose message does not even affect himself can hardly expect it to affect others. The preacher cannot be someone who is given to excess and worldliness and then preach that men and women should turn their backs on the world.