Cannabis Use Is Linked to Lower Obesity Prevalence, but the Study Cannot Show Why
A large U.S. survey found that adults with obesity were less likely to report recent marijuana use than adults without obesity. But the observational study does not show that cannabis prevents weight gain or causes weight loss.
The study, published in 2026 in Cannabis and Cannabinoid Research, analyzed responses from 735,921 adults who participated in the Behavioral Risk Factor Surveillance System (BRFSS) between 2016 and 2022. Researchers led by Ray M. Merrill of Brigham Young University examined self-reported marijuana use alongside body mass index (BMI) and other demographic and health factors.
The BRFSS marijuana questions were part of an optional module offered in selected states and territories, rather than the entire survey population. Participants were classified as current users if they reported marijuana use within the previous 30 days. Daily use meant using marijuana on at least 20 of the past 30 days.
Across the study period, adults with obesity reported current marijuana use at a rate about 35% lower than adults without obesity. The pattern remained after the researchers accounted for factors including age, sex, race and ethnicity, education, employment, tobacco-smoking history, marijuana legalization status, asthma, arthritis and depression. In 2022, the adjusted odds of current marijuana use were 0.68 among adults with obesity compared with those without obesity; the corresponding odds for daily use were 0.69.
The analysis also found a gradient across BMI categories: as BMI classification increased, the odds of reporting current or daily marijuana use generally decreased. Adults classified as underweight tended to report marijuana use more often than adults with obesity. These results describe an association between cannabis use and weight status—they do not establish that marijuana use produces a lower BMI.
Several explanations are possible. People who use cannabis may differ from nonusers in physical activity, diet, alcohol use, medication use, income, access to health care or other factors that were not fully captured in the analysis. The relationship could also operate in the opposite direction, with body weight or health conditions influencing whether someone uses cannabis. Because the study was cross-sectional, it cannot determine which behavior came first.
The study relied on self-reported height, weight and marijuana use. BMI is a useful population screening measure, but the CDC notes that it should be interpreted alongside other health information. In addition, the optional cannabis module was administered in different jurisdictions across different years, which limits how confidently the findings can be generalized to every U.S. adult.
The findings are consistent with other research from Merrill and colleagues examining cannabis use and physical activity. In a separate analysis of the same broad BRFSS period, the researchers found that cannabis use was not uniformly associated with inactivity and that the relationship varied according to whether use was medical or recreational. That study likewise measured associations rather than proving that cannabis changes exercise behavior or body weight.
Whatever its relationship with BMI, cannabis has established health considerations. The CDC identifies risks including impaired attention and decision-making, cannabis use disorder, cardiovascular effects and possible mental-health complications. Frequent use can increase the risk of dependence, and impairment can make activities such as driving unsafe.
The survey therefore raises a question for future research rather than offering a weight-management strategy. Longitudinal and clinical studies would be needed to determine whether cannabis has any direct effect on metabolism or body weight, and whether any potential effect differs by product, dose, frequency of use or medical condition. For now, the most defensible conclusion is that marijuana use and obesity were inversely associated in this large survey—not that cannabis protects against obesity.
