I've seen my friend today, and asked him how the vaping went. He said he vapes 3 or 4 puffs whenever he feels a pang of hunger, and that suppresses it. After vaping, he feels "a ball in his stomach as if he was both hungry and full" (sic) and, a few minutes later, the hunger goes away. He said he hasn't snacked outside meals since he's started vaping. Amazing!
He's still on his first tank and it's still 3/4 full after a few days. At that rate, the 2 bottles I got him will last him a year. Very economical

The only downside of vaping for him is, he reports waking up with a sore throat and stuffed nose every morning. But he seems happy with it.