I actually gained 10 lbs, but I worked at it. It's a lot easier to eat when a) you aren't on like 7 meds and 5 inhalers, b) eating doesn't interrupt "smoking" time, LOL, and c) Food has this interesting thing called "taste."

I really had no idea what food could taste like after smoking for decades...
But, seems to me that the nic is the most likely "offender" when it comes to not gaining weight, since it's a stimulant. I do vape a lot of dessert flavors though, so when I gained weight it was mostly on healthy stuff, like vegan protein shakes with frozen fruit, yoghurt a raw egg (yes, I know, I even saw my little brother get salmonella, but it has been my observation that if you get good, free range eggs, it's fine) milk and OJ.... That and a bunch of raw veggies and fruits and stuff.
I'm happy to not be totally emaciated anymore, but (IMO) to gain weight while vaping, you do really need to Eat Moar.

Otherwise, it's pretty much a straight crossover for most people. IDK if 0 nic would work, but it would certainly fulfill the hand-to-mouth thing, so possibly. I also tend to exercise more than when I can't breathe, but I am super excited to return to my regular bra size, that is for sure....
Anna