Despite their reputation for getting the 'munchies', people who regularly toke weigh less than others, a new study has found.
Researchers examined weight data belonging to more than 33,000 people over three years, and found not only did marijuana users gain less weight than others in that time, they weighed on average just under a kilogram less overall.
"We found that users, even those who just started, were more likely to be at a normal, healthier weight and stay at that weight," said study leader Omayma Alshaarawy of Michigan State University.
"Only 15 percent of persistent users were considered obese compared to 20 percent of non-users."
She said while the difference - about 900g - isn't much, it showed up "in more than 30,000 people with all different kinds of behaviours".
It's not clear why, but weight paranoia is one explanation.
"It could be something that's more behavioural, like someone becoming more conscious of their food intake as they worry about the munchies after cannabis use and gaining weight," said Dr Alshaarawy.
"Or it could be the cannabis use itself, which can modify how certain cells, or receptors, respond in the body and can ultimately affect weight gain."
No one should start smoking weed just to lose weight, she warned.
"There's too many health concerns around cannabis that far outweigh the potential positive, yet modest, effects it has on weight gain."
The study was published in the International Journal of Epidemiology.