The Brazilian butt lift can be done in patients. This procedure is a liposuction and fat injection. What you're doing is changing storage areas of fat. The problem areas are the areas gain weight 1st and lose weight last. This happens because these areas have a higher concentration of fat cells in the normal area next to it. With the fat transfer remaking the buttocks primary storage. another reason why Brazilian butt lift can work in a thin patient is because when you narrow the waist with liposuction the buttocks looks bigger.
I have done this procedure on thin patients have had very good results, taken patients with little shape and made them curvy with an hourglass figure. You don't always have to have a lot of fat to make a change in the figure.