Does Tetrahydrocannabinol (THC) store in body fat?

THC Storage in Body Fat

Yes, THC (tetrahydrocannabinol) is highly lipid soluble and accumulates significantly in body fat tissue, where it can be stored for extended periods and gradually released back into the bloodstream. 1

Pharmacokinetics of THC and Fat Storage

Absorption and Distribution

• THC is highly lipophilic (fat-loving), which allows it to rapidly distribute into adipose tissue after absorption 1, 2
• Bioavailability varies by consumption method:
  • Inhaled THC: 10-35% bioavailability, peaks in blood within 6-10 minutes 2
  • Oral THC: Only 4-12% bioavailability due to first-pass metabolism in the liver 2

Fat Storage Mechanism

• After absorption, THC is rapidly taken up by adipose tissue due to its high lipid solubility 2
• THC concentration in fat can be ten times greater than in any other tissue examined 3
• This storage mechanism serves as a protective function, limiting brain exposure to xenobiotics like THC 4

Retention and Release

• Plasma half-life of THC varies significantly:
  • Occasional users: 1-3 days
  • Chronic users: 5-13 days 2
• THC can persist in fat tissue for at least 2 weeks after a single exposure 3
• With repeated cannabis use, THC and its metabolites accumulate progressively in fat and brain tissue 3

"Reintoxication" Phenomenon

Conditions That Mobilize Stored THC

• Lipolysis (fat breakdown) can release stored THC back into the bloodstream, potentially causing "reintoxication" 5
• Factors that promote THC release from fat stores include:
  1. Exercise: Physical activity increases plasma THC concentrations in regular cannabis users, with greater increases observed in individuals with higher BMI 6
  2. Fasting/Food deprivation: 24-hour food deprivation can enhance blood THC levels in those previously exposed to the drug 5
  3. Stress hormones: ACTH (adrenocorticotropic hormone) exposure enhances the release of THC from fat stores 5

Clinical Implications

• THC release from fat stores during weight loss or exercise may explain unexpected positive drug tests in former users 6
• The slow release of THC from fat tissue contributes to the prolonged detection window for cannabis in drug testing 1
• In cancer patients, periods of adipose breakdown (common during cancer treatment) can lead to a gradual release of stored THC 1

Medical Considerations

Drug Interactions

• THC inhibits multiple cytochrome P450 enzymes (CYP3A4, UGT1A9, UGT2B7, CYP1A2, CYP2B6, CYP2C8, CYP2C9, and CYP2C19) 1
• High-risk drug interactions with:
  • Warfarin (very high risk)
  • Buprenorphine and tacrolimus (high risk) 1, 7

Special Populations

• Patients with significant weight fluctuations may experience unpredictable THC effects due to variable release from fat stores
• Individuals undergoing rapid weight loss programs should be aware of potential THC redistribution if they were previous regular users
• Cancer patients may experience unexpected THC effects during periods of cachexia or weight loss 1

THC's high lipophilicity and extensive storage in fat tissue explain why cannabis metabolites can be detected in urine for weeks after last use in regular users, and why effects may persist or recur during conditions that promote fat breakdown.