Fat people are at higher risk of reintoxication from cannabis

Mar 2

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Is someone who fails a urine test despite claiming months of abstinence lying, or just unlucky? The answer is complicated. In some cases, stored THC metabolites can cause a positive test long after use has stopped.

When cannabis is consumed (smoked, vaped, or ingested), the primary psychoactive compound is Δ9-tetrahydrocannabinol (THC). This compound is metabolized in the liver via cytochrome P450 enzymes (CYP2C9, CYP2C19, and CYP3A4) into 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC), which is still active. This is further converted into 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH)—an inactive but highly fat-soluble metabolite.

Unlike THC, THC-COOH is not psychoactive, but it binds to fat cells, where it can remain for weeks or even months in chronic users.

A Real-World Example: The Fat-Burning Effect on THC Storage

Imagine an addict who has been consuming 1 gram of 22% THC cannabis per day for a decade. Suppose this person has a high body fat percentage (30% for men, 40% for women) due to years of heavy use and a sedentary lifestyle.

Now, they quit cannabis in mid-September. By October, their urine tests turn negative. However, in January, they begin a "New Year, New Me" fitness routine—joining a gym, dieting, and losing weight.

Since THC-COOH is stored in fat cells, weight loss triggers fat metabolism, releasing stored THC-COOH back into circulation. This re-release can cause a positive urine test, despite months of abstinence. In extreme cases, someone could test positive nearly a year after last use if they lose significant weight.