I think the previous postings are pointing out a very important aspect of winter camping. That is, “Sleeping bags and thick clothing do not MAKE heat, they PRESERVE heat.” Only your body can MAKE heat.
It does this by minor flexing of the muscles or, in the case of the shivers, major flexing of the muscles. Anything that involves the use of muscles is work and work requires energy. Where does energy come from for the body? …. Food. So, it is critically important to take enough of (and the right kind of) food to provide the needed energy. I for one would love to read more articles at BPL about nutrition/energy foods for cold trips.
The second part of the equation is “energy used.” In the summer, we can hike until we are panting like a dog and then sleep like a baby all night. However, if we don’t plan our winter trips considering the amount of exertion required, there may not be enough energy left over for heat production at night!
So, it seems to me that gear list planning for winter excursions needs to consider the choice of food just as importantly as the choice of a sleeping bag and, trip planning needs to strive to keep enough energy reserves for a good night’s sleep.