I was losing weight steadily when I was sitting on my ass recovering from surgery. I stopped losing weight when my training plan kicked into gear. I am tracking my food religiously (I am still trying to convince myself to give up the food journal: I can't quit you!). I know my calories are in check.
My husband stopped losing weight as soon as his running was picking up and his long run was over two hours.
Is exercise slowing our metabolism? Are we becoming more efficient?
Or, another possible explanation is "set point" (excellent explanation from Lyle McDonald linked here). Both of us are now at weights that we have maintained for some time in the past, for better or worse.
Both of us want to lose 10 lbs before the Pittsburgh marathon (him) and half marathon (me) this May.
Back to the drawing board......