Allow me to answer your question as best i can based upon your photos. However, please keep in mind that an in-person consultation with physical exam is first necessary before any legitimate evaluation or final surgical recommendations can be made. That being said, your are way too lean for fat transfer and it will be a guarentee failure. The only way to correct this much volume asymmetry is with a buttock implant, custom design if necessary. Buttock implants also provide a permanent result whereas most fat transfer melts away within the first 9-12 months. Finally, do not let any surgeon tell you to gain weight for fat transfer as this always fails as well unless you are willing to stay 20+ pounds overweight post-operatively forever. Hope this helps.