As a fitness competitor I was wondering if it makes any sense to get a BBL?

A good candidate has enough fat available for transfer in the procedure. The amount of fat that can be transferred in a BBL depends on how much fat the patient has to harvest and the amount of space there is to move the fat into. It is recommended for the patient to have a BMI of 30 or less. If you are too thin, a Brazilian Butt Lift may not be possible.

During the procedure, fat from one area of the body is removed via liposuction, and then injected into the buttocks.  During the healing process, those fat cells make your derriere their home. They will fluctuate the same way fat in other areas of your body do with weight gain and loss.  There is no way to determine whether or not significant weight loss and subsequent weight gain will alter the effects of your procedure. Once the fat is lost, it is impossible to determine if will be gained where it was originally implanted.  Fat transfers also require you to have a certain amount of fat in your midsection, hips and thighs. Minimal fat in those areas will mean minimal fat transferred to your backside.  Furthermore, when excessive amounts of fat are removed from one area of the body (as would occur with liposuction), when you are in the process of gaining weight, fat is less likely to be stored in the areas where it was taken from.  This can lead to fat storage in alternate areas; areas where you may not have gained weight before.  My suggestion would be to consult with a Board Certified Plastic Surgeon with experience and expertise in BBLs.  They will be able to truly assess whether or not this procedure is right for you.  

No one can guaranteee results. If you lose weight the fat that is present in your buttock will shrink. The opposite will happen if you gain weight.