I'm not sure if vaping curbs my appetite, but the benefit for me is that when I'm sitting around at night watching TV, instead of snacking to try and make it to the next commercial for a smoke, I can just sit there and vape; I only have to get up at the commercials if I want something more to drink, or need to go let out what I've already drank -- tea does have that effect, even decaf.
That's a huge plus, because I used to go thru some serious quantities of chips, cookies, and various other snacks, none of them healthful! Well, maybe some canteloupe now and then.
I don't think my metabolism has really changed much from switching from smoke to vapor, but in general, it's declining, due to my age. Which sucks, but definitely beats the alternative.
Andria