Will you lose BBL results if you do a gastric bypass surgery 3 years later?

Hi and welcome to our forum!
Health trumps cosmesis. If a weight reduction surgery is being considered, it's purpose is to improve your overall health. 
Following a bariatric procedure, weight loss will be generalized. You WILL lose some or all of the BBL result (it is unpredictable).  The health benefits outweigh the BBL benefits by far.
Best wishes...

Hello dear!
Thanks for the question and provided information as well.
After a BBL, you lose or gain weight in the same way as before. So the answer is yes, if you lose a considerable amount of weight, the results of your surgery will be affected.
If you have any concerns, I suggest you to follow up close with your plastic surgeon.
Good luck :)

Thanks for the question.Whenever you lose weight, you never know what part of the body will get smaller.  Your health is more important so if you are considering losing weight via the gastric bypass, do it anyway and do not worry about the potential for fat loss from your buttocks.Best of luck.Dr T