I am 70 years old in good shape. Am I a candidate for a Brazilian But lift?

Thank you for your question. There is not a specific age, but first, for safety reasons, to be a good candidate for the procedures you want at the same time, your labs and  cardiovascular preoperative evaluation must be optimal.
Kind Regards,Dr. Emmanuel Mallol Cotes.-

Your age by itself will not prevent you from having a BBL  or achieving lasting results.  Your general health, genetics, exercise habits, dietary habits, weight, and other factors must be considered.  Most plastic surgeons prefer that the BMI be near 30 and a stable weight maintained for several months prior to the surgery to lower the risks of complications during and after surgery and to provide maximum results.              
Liposuction will remove the excess fat on your sides, abdomen, and back and make the waist as small as possible. The fat harvested can be transferred to the buttocks to improve roundness and projection as well as hourglass shape.