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New study suggests pot smokers are skinnier

Updated May 17, 2013 at 2:54pm ET

Updated May 17, 2013 at 2:54pm ET

Could marijuana be the secret weapon in solving America's obesity problem? A surprising new study published in the American Journal of Medicine suggested the health benefits of smoking pot may extend beyond pain relief.

Researchers at Beth Israel Deaconess Medical Center, the University of Nebraska and the Harvard School of Public Health conducted a study with 4,657 adults from 2005 to 2010–out of which 547 identified themselves as current marijuana users and 1,975 admitted to smoking at least once in the past (but more than a 30-day window). Participants got tested on their waist size and glucose, insulin and insulin resistance levels.

“We looked at their ability to handle carbohydrates, the ability of the body to handle sugar, and how well the body metabolizes it," Dr. Murray Mittleman, one of the authors of that study, told msnbc's Lawrence O'Donnell.

The results? The study indicated that current pot smokers have much smaller waist circumferences -- by about an inch, on average -- compared to those who have never lit up, even after taking things like sex and age into consideration. Insulin levels for marijuana smokers compared to non-marijuana smokers were slashed by 16% and insulin resistance went down by 17%. And their "good"cholesterol was higher by three points.

“Several prior studies, actually, have indicated that marijuana users tend to be leaner, despite the fact that they do tend to consume more calories," said Mittleman. “One of the caveats, I would say, about our findings is that it was based on self-report.  And really at this stage, we need much more solid research, including experimental studies, to really provide doctors with the evidence base to make recommendations.”

Support for legalizing marijuana has grown in the past few years, according to a new Pew Poll. The majority of Americans, or 52%, now favor legalizing the use of marijuana. When you break it down by party lines, Democrats’ support increased by 11 points, from 48 to 59%, and Republicans’ support jumped by 13 points, from 24 to 37%.

Right now, 18 states along with the District of Columbia allow the use of medical marijuana. But Illinois may be the next one to join that group.

On Friday, the state's Senate approved legislation that permits doctors to prescribe medical marijuana, sending the bill over Gov. Pat Quinn to sign into law.