That berry stuff doesn't means a Werewolf eats berries in the Wolf state.
Hell, the WW in question could have been living in the wild, living off berries and crap in the day, feasting flesh at nighty.
Oh, and do note:
There are two forms of a Werewolf, there is the kind from Daggerfall, which is capable of transformaing once per day, at any time, forced to transform on the full moon and invicible to anything but Silver, and then there is the kind from Bloodmoon.
Having played only the latter, i can say that THAT kind is bloodthristy. You almost died if you didn't kill something. I wouldn't say you lose TOTAL control, but rather, the urges are almost uncontrollable, that you feel as if you *must* obey them. But they can be resisted witth extreme effort.
Of course, so many people think its' unstoppable, they can't summon the will to not be a beast.