Emily
I've been CADing for 8-10 years. Most years I've just lost the weight in summer that I put on in the winter due to the effects of SAD. However, since I've moved from Boston, MA to Washington, DC my SAD has gotten better and I've lost 150 pounds over three years including/accounting for my SAD increases every winter. I am sure that I will reach my goal in another 2 years or so.

As I said before, everyone's weight fluctuates from day to day and due to PMS and TOM effects as well. That is why the Hellers recommend that you weigh daily and average weekly. This allows you to see the true downward trend of your weight without freaking out over the daily ups and downs.