What are the factors one would not be a candidate for BBL?

Hi... thank you for the question... A Brazilian Butt Lift in my practice is not done:Patient do not have fat to be harvestedHave a history of silicone gel injection on the buttock area Other cases can be done without problem. 

Hello dear!
Thanks for the question and provided information as well.
Your BMI is within the recommended range, but unfortunately, without pictures, it is very difficult to give you a proper answer.
In general, you need to be physically healthy and at a stable weight, have realistic expectations, be a non-smoker and your BMI needs to be 30 or less.
l recommend you to make an appointment with a board certified plastic surgeon to talk about your goals and anything you need to know.
Good luck :)

If a person does not have enough fat in other areas of their body to transfer to the buttocks, then they would not be a good candidate for a BBL.  

Do not lose any weight just make sure you are at your comfortable weight; this is the weight that you don't have to stress about. Remember that your BBL will transfer the fat from undesirable areas to your more desirable buttocks region.  At 5'0" and 160 pounds, you should have enough fat to achieve excellent results.