Current Marijuana Users Had 16% Lower Fasting Insulin and Smaller Waist Circumferences | Research

The takeaway

In a nationally representative sample of 4,657 adults, current marijuana users had 16% lower fasting insulin levels, 17% lower insulin resistance scores, and smaller waist circumferences compared to non-users.

Read this if you are interested in the metabolic effects of cannabis use.

16% lower fasting insulin and 17% lower insulin resistance in current marijuana users

What the researchers found

Using NHANES data from 2005-2010, researchers compared metabolic markers between 579 current marijuana users, 1,975 past users, and never-users. After adjusting for age, sex, race, alcohol use, tobacco use, income, physical activity, and BMI, current marijuana use was associated with 16% lower fasting insulin (95% CI: -26% to -6%) and 17% lower HOMA-IR (95% CI: -27% to -6%), an established measure of insulin resistance.

Current users also had significantly smaller waist circumferences. Past users showed intermediate values between current and never-users. No significant dose-response relationship was found among current users.

Why it matters

Lower insulin resistance is associated with lower risk of diabetes, cardiovascular disease, and metabolic syndrome. If the association with cannabis is causal, it could explain the epidemiological observation of lower diabetes prevalence among cannabis users and have implications for metabolic disease treatment.

The numbers in context

4,657 adults. 579 current users, 1,975 past users. Current use: -16% fasting insulin (CI: -26, -6). -17% HOMA-IR (CI: -27, -6). Smaller waist circumference (significant). No dose-response among current users.

How the study worked

Cross-sectional analysis of NHANES 2005-2010 data. 4,657 adults. Self-reported marijuana use in a private room. Fasting blood samples after 9-hour fast. Multiple linear regression adjusting for demographics, lifestyle factors, and BMI.

What this study cannot tell us

Cross-sectional design cannot establish causation. Cannabis users may differ from non-users in unmeasured ways (diet, lifestyle) that affect insulin. Self-reported cannabis use may be inaccurate. The lack of dose-response is difficult to explain if the effect is real. Adjustment for BMI may be over-adjustment if cannabis affects BMI.

How to read the evidence

Large nationally representative sample with appropriate adjustments; moderate evidence for metabolic association.

When this study was published

Published in 2013. This study generated significant interest and further research into cannabinoids and metabolic health.

The bigger picture

This is one of the strongest population-level studies linking cannabis use to favorable metabolic markers. The results are consistent with the endocannabinoid system's known role in metabolism and the finding of lower diabetes rates among cannabis users in other epidemiological studies.

Questions still open

Is the insulin-lowering effect caused by cannabis or by characteristics of people who choose to use cannabis? Would a clinical trial of cannabinoids in pre-diabetic patients show insulin improvement? Does the type or method of cannabis consumption matter?

Common questions

Does marijuana lower the risk of diabetes?

This study found that current marijuana users had lower insulin levels and less insulin resistance, both of which are associated with lower diabetes risk. However, this is an observational association that cannot prove cannabis prevents diabetes. People who use cannabis may be healthier in other ways that were not measured. Clinical trials would be needed to determine if cannabis actually improves metabolic health.

How could marijuana affect insulin?

The endocannabinoid system plays a well-established role in metabolism, appetite, and energy balance. Cannabis may modulate this system in ways that improve insulin sensitivity. Alternatively, the anti-inflammatory effects of cannabinoids could reduce the chronic inflammation that contributes to insulin resistance. The exact mechanism remains unknown.

Read the original research

The impact of marijuana use on glucose, insulin, and insulin resistance among US adults.

The American journal of medicine, 126(7), 583-9

View on PubMed ↗Publisher’s paper ↗

Citation

Penner, Elizabeth A; Buettner, Hannah; Mittleman, Murray A. (2013). The impact of marijuana use on glucose, insulin, and insulin resistance among US adults.. The American journal of medicine, 126(7), 583-9. https://doi.org/10.1016/j.amjmed.2013.03.002