I've always found that being active...particularly being COMPETITIVE, makes it harder for me to lose. Exercise makes me hungry, especially if I'm training hard for a race. I have never been able to lose weight when competition or many hours/week of activity are my focus. I have always lost weight when I'm exercising little, but really focusing on food/calories.

BUT -- keeping weight off. For me that's very much related to activity. Because I can't eat like a bird forever. I'm good eating at a deficit or low calories for only a month or two before I want to hurt somebody.