What should my BMI be for a BBL?

There is no ideal BMI, but I look for one below 32.  You can realize significant results if you select a board certified plastic surgeon who specializes in liposuction and BBL for thinner patients.
Kenneth B. Hughes, MD, Board Certified Plastic Surgeon
Los Angeles, CA

Patients interested in BBL often ask questions of the necessary volume for transfer or the weight gain needed for a particular result. Ultimately, the answer is two pronged and based upon both patient expectations and the nature of fat graft themselves.
BBL and fat transfer is ultimately dependent upon the long term viability of the fat grafted. That being said the resorption rates of fat transferred can be significant. Clinically this translates to a progressive loss of grafted volume in the months following the procedure.
I tell patients that they can expect resorption or graft loss on the order of 50% (at most; prepare for the worst and hope for significantly better). Additionally some harvest volume is lost in processing the fat graft prior to transfer. Thus I generally recommend that patients seeking even the most minimal volume increase have adequate reserves for grafting of 500 cc per cheek (at minimum).  This means that harvest will usually exceed 1 liter (assuming for processing loss).
However, it important to remember that these are recommendations and can be amended 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.
With regards to your specific question, it is difficult to comment on candidacy without photos. However, at your height and weight it is unlikely that you will have significant reserves for transfer. The best candidates are healthy and have reached a healthy stable weight (preferably with a BMI < 30).
As always, discuss your concerns with a board certified plastic surgeon (ABPS).

BMI, or Body Mass Index, is used in surgical risk assessment and a quick calculation notes that you're your BMI indicates you are a good surgical candidate (based on that alone).As for using BMI as an indication of whether you have enough fat for a Brazilian Butt lift, that depends on where and how the fat is distributed and what your specific goals actually are. Look to find before and after photos that include patient information (height and weight specifically) to gauge what kinds of results might be possible. And, as always, be sure to consult with board certified plastic surgeons experienced with fat grafting procedures who can listen to your desired outcome goals and advise you as to whether those goals are achievable given your case specifics.Best wishes!