I am 5'4", 135lbs. Is 1200 cc per butt cheek a drastic change? 1 week post-op.

About 50% of the fat that is transferred lives and becomes a part of you.  This will hold stable as long as there is no weight fluctuation.  The transferred fat will not move, but losses in weight will distribute differently.  The fat that lives in the buttocks from the procedure will get larger with weight gain and smaller with weight loss.  High protein content after liposuction is a good idea, but caloric restriction may not be the best idea for rapid or best healing. 
The results immediately following surgery will be the largest due to swelling and lack of fat resorption.  The buttocks will continue to decrease in size for the first few weeks.   I have observed that between 4 and 6 weeks the buttocks tend to stabilize in volume.  Usually by 3 months, the swelling is minimal and totally resolved by 6 months.  

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

Dear 12312345123,I instruct my patients not to sit for 2 solid weeks. We provide them a specialized pillow that our patients can sit on during that time. They can sleep on their stomachs or sides. Fat viability depends a lot of surgeon technique. The fat has to be placed back into the buttocks as soon as possible so that it has a greater chance of survival. It has to be placed carefully so that not too much fat is placed in only one area.Daniel Barrett, MD, MHA, MS 
Certified, American Board of Plastic Surgery  
Member, Am. Society of Plastic Surgery

Don't do anything in an attempt to kill off the fat as you can change the shape. You may lose up to 50% of what was injected. 600cc per side is not that big, so just be patient. Fat loss can occur for up to 6 months after the surgery. At one week you are swollen and have not lost any volume yet.