> I've heard only anecdotal reports of this, on one of the lowcarb
> "technical" lists.  I.e., some people have done extended Atkins
> induction/ketosis and had thyroid function tested and found that it
> slowed--very possibly the "winter mode" effect you mention.

"Anecdotally", I have noticed this "winter mode" in myself. It is much
harder for me to shed fat in the winter than in the summer, regardless of
activity levels. In fact, I would say that during the summer it *almost*
doesn't matter what/how much I eat - I lose excess fat very easily then.

I think an internal mechanism exists that attempts to preserve fat stores
during fall/winter months when food sources were generally inconsistent.