Do I need to gain weight for a BBL?

I generally do not believe weight gain pre-operatively is a good idea. This is true especially considering the fact that post-operatively some patients will struggle with losing the weight again. The optimum surgical candidate has reached a healthy and stable weight. 
This issue often comes up when discussing BBL and fat transfer. For these patients, adequate donor sites for harvest are necessary. The question of "adequate" will vary from one patient to the next. Your board certified plastic surgeon is uniquely suited to asses whether you have the reserves to meet your goals.
If you have reached a healthy stable weight (preferably with a BMI less than 30), the focus should be on maintaining. I typically do not recommend gaining/losing weight for the sake of surgery alone (weight loss for the sake of your health is a different story). It is important to remember that weight changes post procedure can potentially compromise the results of your buttock augmentation (as transferred fat can change with weight just as it could prior). If you plan on losing weight, I would do so before surgery and plan on maintaining afterwards. Weight gain should be discouraged unless you plan to maintain post operatively (or else the fat gained and transferred is typically the first to go post op).
Ultimately, decisions are based upon a patient's particular expectations. Some patients only want a subtle change and may be willing to accept a less significant result. But the rule still applies you have to have the fat to transfer the fat.
As always, discuss your concerns with a board certified plastic surgeon (ABPS).

While gaining weight before a procedure is not recommended, If you were to do this then it is important that you maintain the weight. If you were to lose the weight after then the results of the procedure would shrink as well. 

Hello cherrydoll, 
I appreciate your questions! Many of my patients who desire a fuller, beautifully rounded backside opt for Brazilian Butt Lift (BBL) surgery. One of the main considerations when evaluating a patients’ candidacy for Brazilian Butt Lift surgery is whether they have enough fat stored in their body so the surgeon can harvest enough fat cells to use during the fat transfer phase. For patients with insufficient fat deposits, the doctor may advice weight gain before the BBL to qualify for the procedure. Set up an in-person evaluation with an experienced plastic surgeon to assess your BBL’s candidacy and discuss your specific needs and aesthetic expectations. Good luck and may God bless you! Dr. De La Cruz.   

With a Brazilian Butt Lift, the amount of volume that can be added to the buttocks depends on the amount of fat you have in your abdomen, flanks, bra rolls and thighs to be removed via liposuction, and then transferred to your butt.  Even with minimal fat to transfer, a BBL is oftentimes possible as long as the client is looking for natural, athletic looking bottoms as opposed to a round, voluptuous one.  There are many different butt shapes, and if done correctly, a small amount of fat can add a subtle lift. Sometimes a small modification can make a big difference.
For my thinner clients looking to obtain a fuller derriere than what a BBL would provide, I typically recommend using fillers to enhance their butt size.  The use of an injectable poly-L-lactic acid helps stimulate the body's natural collagen production, which adds volume to the area. 
Always choose a board certified plastic surgeon with experience in these procedures.  Best wishes!

Hello dear!!
Thanks for the question and provided information as well. 
Unfortunately, without pictures is very difficult to give you a proper answer.
I recommend you to make an appointment with a board certified plastic surgeon for a good evaluation and to talk about your goals.
Good luck :)

Hello, and thank you for your question.  It is very hard to give you much of a reasonable answer without at least photos.  At your height and weight you may simply not have enough donor fat to transfer.  I have operated on women that appeared slight, and ultimately had more than enough fat to dramatically augment their buttock.  Butt Implants have become more popular and standard for patients who are not candidates for a BBL in recent years.  The scar is very well hidden, results can look very natural or be very large-dependent on the patient's desires.  The most important thing is to have realistic expectations and go with a procedure that will help you achieve your body goals vs what you may have originally had in mind.  All the best moving forward.
Dr. Grewal
Beverly Hills, CA 

Hello
It is hard to say what would be right for you without pictures.
You definitely must be evaluated first to coordinate with procedures
will fit your needs. Visit a certified plastic surgeon to accomplish
what you wished. Best wishes.
Regards
Dr. Israel Mañon
Certified Plastic Surgeon

Thank you for your question, When we do the patient examination, we ask the patient there expectation and accordingly we access there donor area. If the expectation meet the result we go ahead and if requirement is more and the fat at donor area is less we suggest them to gain some weight and come back, Though we explain the patient what can be achieved at her current body weight and the fat percentage that she has. If you are not very keen for weight gain you can also get a repeat procedure done as and when you feel.