For many years, and I'm 46 btw, I would put on 10-15lbs from Sep through March and then lean out in the summer. When I hit 35, I'd put on 10-15lbs in the winter, and not lose any in the summer. I think I started using winter as an excuse to eat whatever I wanted get as fat as I wanted, but age and metabolism didn't let me get away with that for too long. I started Primal in Jan 2011, and lost 60 lbs this year, and am happily at my goal weight and in a 'normal' BMI for the first time in 20 years. As this winter came on, I found my old habits creeping back.
So, for the rest of the winter, I've decided to yoke my carb intake to the sun. As we get closer to Dec 21st, my carb intake will decrease to nearly zero carb and as the daylight gets longer after that I will add more carbs back in. I think this is a natural progression of carb intake as our ancestors would have had less starchy foods to choose from in the winter (at least my northern Euro ancestors, anyway).