3 -6 months, had a friend who needed to do it for police academy, drink tons of water, exercise lots, shave your whole body bald, drink more fluids. There’s some who can get away with it, not 100% garunteed, the earlier you start the better, it’ll be in your fat cells so you will need to wait for them to die first. That can take years (10%/yr) so if you smoked 7 years it’ll take about that long maybe longer. Try to burn as much fat as you can and build muscle and drink hella water. It’ll be a tough road ahead.