http://www.imperial-library.info/content/hircine
"The hunger or the Bloodlust of the Lycanthropes is legendary. Unlike Vampires that can survive without blood for a period of time, the Lycanthropes cannot. They have to kill once they have turned to beast form otherwise they would die."
http://www.uesp.net/wiki/Lore:On_Lycanthropy
"My conclusion is that they do not need to attack and devour humans to survive. Yet, for some reason they do."
So which fact is correct? Obviously the first one. Both Daggerfall and Bloodmoon shows that a werewolf must kill a living person to wake up healthy in the morning. Otherwise they will die, so the book is incorrect on that matter.
Both are. In DF, not killing would kill you eventually. In Bloodmoon, you wouldn't die, but you would gain penalties to stats.