“There are limited data regarding the relationship between cannabinoids and metabolic processes. Epidemiologic studies have found lower prevalence rates of obesity and diabetes mellitus in marijuana users compared with people who have never used marijuana, suggesting a relationship between cannabinoids and peripheral metabolic processes. To date, no study has investigated the relationship between marijuana use and fasting insulin, glucose, and insulin resistance…

Conclusions

We found that marijuana use was associated with lower levels of fasting insulin and HOMA-IR, and smaller waist circumference…”

http://www.amjmed.com/article/S0002-9343(13)00200-3/fulltext