Why are marijuana smokers not overweight?

Many are overweight. Two research studies that made the news in 2011 found 14%-17% of marijuana users (3 or more times/week) were obese. Presumably, many other mj users were overweight but not obese. Their findings in people who did not use mj showed 22%-25% of non-users were obese. Perhaps people who tend to become mj users are less obese to start with, or maybe mj users use mj instead of food to soothe their stress.
Unclear. Baseline? . Recent studies have shown marijuana smokers on average to be less overweight than non-smokers, however this might be due to several reasons. Those who smoke pot are a different group to begin with at baseline (lifestyle, cancer patients), they may have different habits (substituting pot for "comfort eating"), or in some people pot increases activity.