I am more sensitive to cold than the average person, in fact more sensitive than anyone I know. I have very little natural insulation.

I find a single layer not enough at about zero degrees C, particularly when it is windy. However, as a woman, I have an option that might be too far out of the envelope for most men: nylon panty hose. They are remarkably warm, extremely light, quickly and easily washed, and dry quickly. Long johns -- sweaty, dirty, a pain to wash, ugh.

I have been comfortable hiking at -15 C with the panty hose layer under fleece pants. Just pretend you are buying them for your overweight sister; you will find something that fits.

I am more sensitive to cold than the average person, in fact more sensitive than anyone I know. I have very little natural insulation.

On the specific point about acclimitization: people vary a great deal on how quickly and how well they acclimitate. For example I would never, never, never acclimitate to -35 C to the point where I would not need an underlayer.

I find a single layer not enough at about zero degrees C, particularly when it is windy. However, as a woman, I have an option that might be too far out of the envelope for most men: nylon panty hose. They are remarkably warm, extremely light, quickly and easily washed, and dry quickly. Long johns -- sweaty, dirty, a pain to wash, ugh.

I have been comfortable hiking at -15 C with the panty hose layer under fleece pants. Just pretend you are buying them for your overweight great aunt; you will find something that fits.