I do not recommend gaining weight for a BBL as this will only make your fat cells get injured and die during the transfer process. This is because when you gain weight, the fat cells get larger in size thus making them prone to injury as they travel through the small holes of the cannulas used to harvest fat.
The definitive technique for you, since you are thin, is ultrasound-assisted liposuction which should be performed by a high definition body contouring specialist. Additionally, the use of our Buttock Assessment Tool to determine the ideal buttock shape and size for you is critical.