It seems counter-intuitive, given marijuana's reputation for giving people the munchies.  But a new study suggests marijuana users might actually gain less weight than non-users.

Researchers analyzed Body Mass Index (BMI) data for 33,000 participants in the US National Epidemiologic Survey of Alcohol and Related Conditions.  They compared the BMI of marijuana users and non-users over a period of three years.  They found a very small two-pound weight variance between users and non-users that held true across the entire study group of adults 18 years and older.

"An average two-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," said Dr. Omayma Alshaarawy, assistant professor of family medicine at Michigan State University and the lead author of the study.

Not only that, but marijuana users seemed to gain less weight over time than non-users.

"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," said Alshaarawy, "Our study builds on mounting evidence that this opposite effect occurs."

It could corroborate past studies that discovered similar correlations between marijuana use and lower rates of weight gain and obesity.  Now, "why" that happens is still an open question.  It could be that marijuana users adapt behavior to counter-balance the extra calories, or that cannabinoid compounds in marijuana might alter metabolism in the opposite way popularly assumed.