How long after BBL can I go back to heavy weight training?

Always ask your plastic surgeon about specific activities and when they can be resumed after surgery.
However, if you are asking this question hypothetically, my response is working out may increase the muscle mass and in turn improve the shape.  I usually ask my patients to wait from 4 to 6 weeks, depending upon healing.  
As a bodybuilder, I understand the need to return to the gym, but healing should be far enough along to reduce the incidence of complications.  As a board certified plastic surgeon, I advocate continued weight lifting and exercise after a BBL as long as you do not lose body fat.  Keep an eye on your weight, and decrease the amount of exercise as warranted.

Kenneth Hughes, MD, Board Certified Plastic Surgeon
Los Angeles, CA

This is different depending on your doctor. You should definitely ask them what their recommendation is. I tell my patients to wait 4-6 weeks before working out. When they start back, they are to start slow and then work their way up to the hard/heavy stuff over several weeks/months. If anything is uncomfortable, I tell them to back off and try again in a few weeks. 

I usually allow patients who have had BBL  to start exercising within 3-4 weeks after the procedure. Best to ask your doctor.