The Effect of Legalized Marijuana on Weight

Does increased legal access to marijuana mean we will become slimmer or heavier?

Posted Apr 02, 2019

Marijuana munchies seem to have been around as long as s’mores, a gooey, melted marshmallow, chocolate and graham cracker creation favored by marijuana inhalers. Indeed, gobbling fatty-sugary or fatty-salty crunchy foods seems to be the inevitable aftermath of marijuana use. Now that more and more states are making this drug legal, and shops selling it as ubiquitous as Starbucks, will consumption of junk food increase to new heights? And will the weight of the country follow? 

The effects of smoking two cigarettes of marijuana or a placebo on food intake and weight was studied more than twenty years ago. Six male volunteers lived in a residential research facility for 13 days and their food and activity monitored after marijuana inhalation or placebo. Smoking marijuana increased daily calorie intake by 40%, and the calories came primarily from junk food like candy bars and potato chips. The subjects’ weight increased as well. 

Current market research on the sales of junk food in states where marijuana use is now legal seems to confirm the results of this early study. An article in Medical News Today March 2019 reported a relationship between states where recreational marijuana use is allowed and sales of junk food: Monthly sales of ice cream, cookies, and chips increased from 3 to over 5 percent, respectively, compared to sales before recreational use of marijuana was legalized.

The Internet is filled with suggested snacks for those whose mouths are yearning for sugar and fat, and there are even snacks for the keto folk who prefer their fat with protein.  Research has identified one of the many components of marijuana, tetrahydrocannabionol ("THC"), as responsible for triggering hunger. Indeed, the effect is so potent that clinicians have suggested its use in stimulating appetite in patients who have none, such as cancer patients.

Yet before pot shops start selling clothes in extra large sizes to meet the needs of their customers, it is important to note that marijuana may have an entirely opposite effect on appetite and weight. A review of studies looking at weight change with marijuana use did not find data unequivocally confirming increased food intake and body weight among users. The authors report the results of studies in which marijuana was used to increase weight among patients with HIV or cancer, and found that although appetite seemed to be stimulated, the weight gain was not clinically significant.  Conversely, studies looking at large populations of users found them to have lower body mass index than non-users. Explanations for this disconnect between increased appetite and lower weight seem to include everything from how often marijuana is used, whether substance abuse of alcohol and/or other drugs is involved, the presence or absence of mental disorders and THC dose or concentration.

Conversely, there is now a substantial amount of evidence that specific components of marijuana might protect against weight gain. Two large national surveys looked at weight in populations of users and non-users and their results were summarized a few years ago. The two surveys from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC 2001-2002) and the National Comorbidity Survey-Replication (NCS-R, 2001-2003) both found that marijuana users had a significantly smaller prevalence of obesity than non-users.

This ambiguity over the weight-changing effects of marijuana is due in part to the differing effects on appetite of two components of the plant. THC seems to be responsible for munchies, along with the psychoactive effects of cannabis. CBD, or cannabidiol, another of the approximately 100 identified phytocannabinoids, seems to counteract the mood-changing effects of THC and decreases hunger. In June 2018, an FDA approved drug, Epidiolex, that is now used to treat two pediatric seizure disorders, has as one of its side effects decreased appetite. Cannabidiol is the purified component of this drug.

The differing effects the marijuana on hunger has an eerily similarity to what the Caterpillar, in the book Alice in Wonderland, told Alice about a mushroom on which he was sitting. “…the Caterpillar got down off of the mushroom…merely remarking as it went ‘One side will make you grow taller and the other side will make you grow shorter.’ “  Alice nibbles on one side and shrinks; she eats from the other side and grows.

If one smokes or eats, or uses the oils from one component of marijuana, will one get fatter and then switching to the other component, grow thinner?

As expected, the Internet is now filled with pictures and descriptions of various types of marijuana that may help with weight loss. But the recommendations as to how to use these leaves to lose weight could come right out of any weight-loss program: eat healthy, exercise, get plenty of sleep, watch portion sizes. So far, CBD has not been purified and tested in large clinical trials to see its effect on weight and, as important, its effect on acute and chronic side effects.  Nor have there been other studies examining whether CBD might decrease emotional overeating by decreasing anxiety. Should such studies be carried out, they must meet the standards used in testing any weight-loss drug for efficacy and side effects.   

For decades people struggling with their weight have been looking for the “magic pill” that allows them to lose weight easily without the need for will power and self-discipline. Is marijuana the magic pill that will allow some who need to gain weight do so and others lose weight? The answer is still in the future. 


“Effects of smoked marijuana on food intake and body weight of humans living in a residential laboratory,” Foltin R, Fischman M and Byrne M, Appetite, l988; 11: 1-14.

“Marijuana and Body Weight,” Sansone R, and Sansone L, Innov Clin Neurosci. 2014; 11: 50-54.

“Obesity and Cannabis Use: Results from two national surveys,” Le Stat Y, and Le Foll B. Am J Epidemiol 2011; 174:929-33.