We finally figured out why the main floor of our house was a freezer while the top floor was hot as an oven and the basement felt like a sauna. It turns out two of the four vents were either closed or blocked off by stuff carelessly plopped over the vent by our tenants. We cleared it up and the main floor got warmer within a day. But try as we might to balance the temperature throughout the house, there are still some problem cold spots...Cranking up the heat for your entire house just to warm up a small area for yourself is equivalent to starting your car engine just to charge your cell phone. It's a huge waste of energy when all you really need to do is heat your own body.
Why heat up the entire house when you're just occupying a very small portion? Invest in a small/cheap space heater to keep you warm without spending tons of money on the heating bill.
Keep the Heat In and the Cold Out
Particularly in older homes, sometimes the heat is just escaping out energy inefficient windows and doors, poor seals and cracks, crappy insulation, and any number of ways that old (or poorly constructed builder grade) homes waste energy. If a renovation is out of your budget (or out of the question), look into draft seals that slot in between your windows and doors to help block the wind from penetrating your house. Curtains help block drafts as well. Try adding caulking or sealant to cracks. Big rugs help provide further insulation - and think about checking the insulation in your attic/crawl space.
Make use of that treadmill you bought as a new years resolution and get some exercise. No more excuses that the layers of fat are just there to help you keep warm! Or just stay active in general - clean up the house or some other task you've been putting off and get your blood circulation going.
Throw A Sweater On
Invest in a big warm bathrobe, throw on a sweater, put on some slippers, toss on a hat, and pull on some mittens. Low tech and low cost, sometimes no-tech really is the cheapest/easiest/most elegant solution.