I definitely was thinner when I had ACTIVE UC. The reason I say it like that is because we all have a tendency to gain weight as we get older. That said I remember never really gaining weight when my UC was acting up, we're talking 10+ years. As soon as my UC got under control I notice I retain more weight. Not prednisone like weight. When I eat more I wiegh more, when I eat less I can lose the weight very quickly. I guess my body is retaining all the nutrients in regards to what I eat. When I just start losing weight and it's free falling it's usually when my UC is out of control.
MyUC