A thin person can sometimes be a candidate for a BBL, but the result is usually more limited than in someone with more donor fat. At 5'4" and 120 lbs, the key question is not only your weight, but where you carry fat that can be safely removed with liposuction. Some patients have enough fat in the abdomen, waist, flanks, back, or thighs for a modest shape improvement, while others may not have enough donor fat for a noticeable volume change. A consultation should focus on your exam, skin quality, natural pelvic shape, and whether your goal is subtle contouring or a major size increase. For a very slim patient, a skinny BBL may be more about waist and hip contour than dramatic buttock enlargement. Gaining weight only for surgery is not always predictable, because the fat may not go to useful donor areas, so it is better to be evaluated at a stable, healthy weight.