Stroke - often hungry

One thing I do not understand is why I feel hungry so often, yet do not put on weight.

I recently had a bowel cancer check and that was all clear. I eat a very full breakfast (Weetabix, half a banana followed by a cooked breakfast cooked in very little oil) and I have a good lunch and tea, but already I am hungry again! My weight has been pretty constant for over a year - maybe a few pounds heavier. I drink very little alcohol these days and have no sugar in tea or coffee, but I guess there is sugar in the chocolate drinks I have.