If you weigh 165 lbs long does weed stay in your system?

THC is stored in fat cells.

That being said, drug tests work by testing for a tolerance of 50 nanograms per millileter of THC (or whatever drug(s) the test is for) in your system.

Regardless of how much you smoke, for how long you've smoked it, or how much you weigh, you may test positive for marijuana for up to 90+ days. No, one hit will not leave you urinating dirty for 3 months, it's a proportional equation. The more THC in, the longer it stays.

The best way to remove THC from your system is to stop using the drug. To speed up the process, consuming 8+ glasses of water per day, plus a rigorous exercise program to help burn those fat cells would be ideal.

No, detox kits do not work. Nor do detox shampoos. If it's too good to be true, it's not true.
depending on your metabolism it will take 2 to 4 weeks for it to leave your system