For girls with flat butts that are getting a BBL, is it easier to obtain a heart or a shelf booty?

Thank you for your question. It is hard to provided with a valid medical opinion without photos.  I would suggest to be treated by board certificated plastic surgeon with experience in this procedure, to get the best desired results.
Kind Regards,Dr. Emmanuel Mallol Cotes.-

Hello, thank you for the question.
Actually this depends on your body type, but usually patients get a more heart-shaped look.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.
Best of lucks.
Dr. Luis Mejia

Hello, thank you for your question. Fat transfer to buttocks will give you more volume and a heart shape. I would recommend you a consultation with a  certified plastic surgeon to discuss the best options for you.