To folks on a weight loss plateau ... WINTER COMMUTE!
I commuted in this morning in the 32 F degree weather, and I have to say its one of the hardest rides I have ever done. It took me 10 minutes longer than normal (in part because I didnt have a good breakfast, and Ive had a cold) but also because that cold just saps your energy. Its a real challenge, and frankly I think an excellent way to get yourself on the bike and force in extra riding.
It was one of those rides that you just know will knock weight off.
It takes a little experimentation for find out what clothing you need to be comfy riding your bike at lower temperatures. I don't find that I ride much slower when it is colder till the temps get to below 20F and air actually starts to burn your lungs. For riding in temps around 2 to 15 F I now have a XPolar face mask that captures the heat from the air I breath out and then helps preheat the air I breath in. That helps a lot. There is definitely a bit more resistance, but that is better than extreamly cold air rushing into your lungs. Do see the Winter Cycling forum if you are interested in riding through the Winter. There are lots of discussions on what to wear to be comfortable. Most people start out wearing far too much and get overheated.
The other thing that REALY slows me down are the studded snow tires. I just put them on this past weekend as there was frozen precipitation in the forecast for Monday and Wednesday. We didn't get anything bad on Monday, and the snow that is coming tonight will be well South of Buffalo so it won't affect me after all. Going from 700c*32 slicks to 700c*35 Nokia W106's is quite a drop in efficiency. I don't be riding as far in the Winter, so the extra effort makes up for less additional riding.