How safe is the brazilian butt lift? is it long lasting ? and safe for someone who might be very unhealthy ? what age do you recommend to get it done?

More data: Generally, there is a lack of data on the chance of your being injured or dying from the specific procedure you discussed, but for cosmetic surgery in general, the risk is about 1 in 13, 000 for dying; and there is similar risk for general anesthesia, or being put to sleep for the surgery. There are many considerations before such a procedure; ask your primary care provider and a good surgeon.

It's still surgery!: No procedure is safe for someone who is unhealthy at baseline. See a board-certified plastic surgeon. All medical problems need to be looked at so the patient is in the best possible condition before the procedure. Surgery and anesthesia/sedation carry risks for everyone, but they're less for healthy patients. The surgeon will advise on age, timing of surgery, etc.

BBL is Surgery: A BBL is surgery and all surgery carries a degree of risk. If the person is "very unhealthy" they will likely not be cleared for surgery. When done correctly, fat grafts are permanent, success is highly dependent on surgical technique (surgeon) and following post-op instructions (patient). There are no real age requirements other than you should be 18 years old for elective surgery like this.