i find it difficult to believe that there is anyting about vaping itself that could cause weight gain. i would think that it simply has to do will cigarettes ability to speed up your metabolism and once you stop smoking, your metabolism slows back down (to normal) and thus if you make no other lifestyle or diet changes you might begin to gain weight.
i have been vaping for about 2.5 months, and i have gained a bit of weight, but i don't attribute it to vaping, i attribute it to not eating like i should, not enough activity, and eating more because food tastes better now!
i am begining to count my calories again, so it will be interesting to see how this goes. this is the first time in my life i have tried to loose weight and did not have cigarettes around. i am looking forward to it. weight loss + vaping = much healthier life.