Do I have to gain weight for a Brazilian Butt Lift?

Will I have to gain weight if I want to get a Brazilian butt lift? Right now I am 5ft 4inches and weigh about 120lbs. I feel pretty fit and healthy but I want to increase the size of my butt. I will do whatever it takes but it would be nice to know the correct steps to take before I start trying to gain weight.

Corinna-q

F, 35, California