Don't assume dagga will make you fat

Even though marijuana triggers the "munchies" in many people, adults who use the drug tend to weigh less than nonusers, a new study finds.

The finding stems from data on the weight of 33 000 Americans, 18 and older. Researchers found that all gained weight over three years. However, those who used pot bulked up less than those who did not.

Modest weight difference

The study also found that new and persistent marijuana users were less likely to be overweight or obese than nonusers.

"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 lead author Omayma Alshaarawy. She's an assistant professor of family medicine at Michigan State University.

"Only 15% of persistent users were considered obese compared to 20% of nonusers," Alshaarawy said in a university news release.

The weight difference among users and nonusers was modest – about 2 pounds (0.9kg) for someone 5 feet, 7 inches (1.7m) tall who weighed about 200 pounds (90.7kg) at the start of the study.

"An average 2-pound (0.9kg) difference doesn't seem like much, but we found it in more than 30 000 people with all different kinds of behaviours and still got this result," Alshaarawy said.

Marijuana not a diet aid

Because the study only found an association between weight and marijuana use, several factors may explain why users are less likely to pack on excess pounds.

"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," Alshaarawy said.

"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," she added. "More research needs to be done."

Despite the findings, marijuana should not be viewed as a diet aid, Alshaarawy warned.

"There's too many health concerns around cannabis that far outweigh the potential positive, yet modest, effects it has on weight gain," she said. "People shouldn't consider it as a way to maintain or even lose weight."

The study was published recently in the International Journal of Epidemiology.

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