It used to be a truism that when people stopped smoking, they were likely to gain weight, but the reasons for it were cloudy. Did people replace the mechanism of smoking with candy and food, or did nicotine suppress body weight gain independent of food intake. In other words, was it speeding up metabolism
A new paper in Nicotine&Tobacco Research using rats says it is the latter. Caution is always warranted in these sorts of studies, since mainstream media tends to hype animal model findings without ever noting that rats are actually not little people.
In rats self-administering a maximally-reinforcing dose of nicotine, body weight gain during the 20-day study period was attenuated by ~40% despite no change in food intake.