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Researchers say marijuana users actually gain weight more slowly than others. Getty Images

For decades, marijuana use has been associated with the “munchies.”

That stereotypical impulse to eat junk food would lead most people to expect that marijuana users tend to put on weight more quickly than those who don’t.

But new research suggests that may not be the case.

A recent study found people who used marijuana put on less weight, on average, than those who didn’t use cannabis products over a three-year period.

Everyone in the study put on weight. But those who used marijuana put on an average of two pounds less.

The researchers had expected the “munchies effect” to lead to greater weight gain, said Omayma Alshaarawy, a Michigan State University family medicine professor and lead author of the study.

But, she told Healthline, they weren’t “entirely surprised” by the results.

That’s because other studies have also indicated that marijuana users may be slower to gain weight. A 2011 study, for instance, found marijuana users were less likely to be obese than people who don’t use the drug.

Some studies have found cannabidiol, one of the compounds in marijuana, can help aid in weight loss. But whether marijuana use can slow weight gain — and, if so, why — is still an open question.

Studies like the new one try to take other variables into account, but they don’t always prove causation.

That is, marijuana hasn’t been proven to be the cause of slower weight gain — just that people who use it tend to gain weight slower.

So Alshaarawy cautioned that the notion marijuana might cause slower weight gain is only speculation.

If it does, though, it might be due to something in the way marijuana affects the body’s metabolism.

Or it might be due to something in how it affects the user’s behavior — like causing them to try to avoid that old munchies stereotype.

“It might be a behavioral effect as cannabis users are aware of the munchies effect and might therefore restrict their caloric intake when they are not using,” Alshaarawy said. “Further studies are needed.”

The biggest takeaway from research like this is to produce a hypothesis — that marijuana might slow weight gain — that future studies can then test.

That could be useful as governments examine how to regulate marijuana and products made from it.

The drug is now legal for recreational use in 10 states and the District of Columbia. Medical marijuana is allowed in another 23 states.

But research on whether and how it affects weight gain is still lacking.

That leaves us to fill in the image of a marijuana user as a lazy guy on his couch eating junk food, said Jamie Corroon, ND, MPH, founder and medical director of the Center for Medical Cannabis Education in Encinitas, California.

“I think that the image that we have in our heads of the marijuana user may be a little outdated,” he told Healthline.

That stoner image from movies and television, he says, doesn’t necessarily hold true today.

He said people are using marijuana and still are physically active or as an aid to recovery so they can get back into action.

“So it could be that marijuana user are more likely to be active,” Corroon said.

He also would like to see more differentiation between types of marijuana users.

The study separates into those who had never used it, those who had quit, those who had recently started using it, and those who use it regularly.

But the frequency with which people use it might vary a lot within those categories.

So examining questions like whether users are more active than previously assumed would be the next steps he’d like to see the research take.

That’s partly what Alshaarawy has in mind.

She said her team is planning on using animals to look into “potential mechanisms linking cannabinoids and body weight.”

And they want to know more about whether marijuana users’ food intake “is a behavioral mechanism” — like the munchies, or lack of it.