Here is my breakdown on priorities of warmth.
#1 be well hydrated. Blood flow is massively impacted by dehydration. Extremities and skin surface get chilled much quicker when your not as well hydrated.
#2 good calories balance between sugars, fats, carbs, and protein. Sugars warm you up, a piece of chocolate is great just before bed. Carbs and protein takes longer to break down and keeps the engine running. And fats like those in olive oil or butter can help to get the metabolic motor running.
#3 Clean, dry and and loose fitting clothes. Do not wear socks or base layers that fit tightly. If your socks are tight at all, even a little you are better off without them. Down socks can make a big difference in keeping the toes warm. As will a good warm hat.
#4 get up and take a leak when you need to rather than staying in the covers when you need to go. Your body has to maintain the warmth of that fluid and is expending energy on that. When you get up though take a drink of water, if your not in bear country (assuming you can keep food safe and readily accessible) a bite or two of chocolate and then hop back under the covers.
#5 Hot water bottle trick and or the cem hot packs. Put them someplace where they will help keep your core warm and pumping hot blood. I will sometimes put a hot cem pack on the small of my back near the kidneys if it gets really cold. You will be pumping good hot heat though your system. AHE now stocks high quality cem hot packs here: Heat Factory Warmer
The Adhesive ones are great for putting right where you need the warmth the most....Kidneys, feet, or where ever you feel the chill.
Once you account for these 5 factors you will stay warmer than if you ignore these cold weather priorities.
FlameThrower socks are the perfect companion to staying warm in the winter.
Insulate your lower legs with a high quality Foot Pad.
Keep your Head Warm. Our Bear Pillow gives you a warm spot to lay your head down nightly.
I hope that helps to keep you warm though the cold months.
Paul @ Arrowhead Equipment