I've lost almost 40 pounds since I started vaping. I have a craaazy sweet tooth, and vaping dessert flavors has really quelled that. When I crave sweets now, I don't even think about eating the real thing anymore. I just look for the eliquid. One time, I had Blueberry Pie from TV and the real thing in the fridge - the real thing ended up going bad, cuz the eliquid was so much better!
Also, my lung capacity greatly improved after just a few weeks, so I'm able to work out more now. I went from 5-10 minutes on my HealthRider when I smoked to about an hour with weights (built up over a year), and can painlessly/effortlessly climb stairs.
I think what's really worked for me is that giving up smoking has pushed me into improving other things in my life that were bad, like how I eat (I'm a vegetarian now), how much water I drink (I never drank enough before), and how much I work out (1+ hours every other day). I say use it as a tool to better your health (it's quite effective), and the weight loss will happen on its own (if that's what you're going for).