Is it true that marijuana concentrates in the body fat?
Yes, some metabolites (break-down products) of marijuana concentrate in the body fat, but not much of the active ingredient, delta-9-tetrahydrocannabinol (delta-9-THC). These metabolites leak out of the body fat stores slowly, over days or weeks. Thus, urine and blood analyses can tell us that people have used marijuana, but it is very difficult to tell when they used it, since the available urinalysis methods measure primarily the metabolites of marijuana.
