It's a bit early for me to be sure (only been vaping for two weeks today), but to add some more anecdata, I think in my case it seems like vaping will lose me some weight. Much too much of my usual calories comes from a hardcore Dr Pepper fixation. But, since I've been vaping (especially inside where I couldn't smoke before), it seems like I don't have the urge to drink Dr Pepper anywhere near as often, and when I do, I'm much more willing to settle for the Diet Dr P rather than the real thing. I'm supposing that the sweet sweet e-juices are satisfying my sweet tooth, and/or it's just that urge to be doing something like that hand-to-mouth thing. Of course, this is dropping my liquid intake big time, which I guess I should start compensating for.
Now, just waiting to find some Dr Pepper-flavoured e-juice....