April 19 (UPI) -- The joke is that smoking marijuana can cause weight gain because users might get the munchies, but new research suggests that pot smokers weigh less.
The average 5-foot-7 person who smokes marijuana weighs two pounds less than someone who does not, according to a study published in the International Journal of Epidemiology.
The researchers caution that cannabis shouldn't be thought of as a weight-loss aid, but they say the data is clear.
"Over a three-year period, all participants showed a weight increase, but interestingly, those who used marijuana had less of an increase compared to those that never used," Omayma Alshaarawy, assistant professor of family medicine at Michigan State and study lead author, said in a news release. "Our study builds on mounting evidence that this opposite effect occurs."
Researchers compared body mass index, BMI, for 33,000 people over age 18 collected as part of surveys for the National Epidemiologic Survey of Alcohol and Related Conditions. The surveys included computer-assisted personal interviews on cannabis use, body weight and height.
"We found that users, even those who just started, were more likely to be at a normal, healthier weight and stay at that weight," Alshaarawy said. "Only 15 percent of persistent users were considered obese compared to 20 percent of non-users."
Alshaarawy added that "an average 2-pound difference doesn't seem like much, but we found it in more than 30,000 people with all different kinds of behaviors and still got this result."
A 2011 study also showed that obesity among marijuana users was lower, at 17.2 percent, than among those who didn't smoke, at 22 percent.
Still, the researchers warn people not to view marijuana as a weight loss aid. Other studies have linked smoking pot to having a bigger appetite, higher caloric intake and high blood pressure.
"There's too many health concerns around cannabis that far outweigh the potential positive, yet modest, effect it has on weight gain," Alshaarawy said. "People shouldn't consider it as a way to maintain or even lose weight."