"warmth in extremely cold weather"

They couldn't keep my legs warm for a 90 minute walk in 30 degree Michigan weather (windchill 25ish). Wearing these definitely keep me warmer than not wearing these, but I don't understand how they could keep anyone warm in extremely cold weather unless the person were running.

BTW: I'm 6'4"@175lbs and size M of these fit okay. Because they have to stretch so long to cover my legs the crotch pulls down a bit far, but otherwise the fit is not bad at all.

UPDATE:
Despite all my complaints about these I have worn them just about every cold day since I've bought them and they've made all the difference this winter. Without these I would be miserably cold.