Congratulations on your journey. An in-person exam will ultimately help determine whether you are a good candidate for a feminizing BBL, as well as the degree of improvement you might achieve. Looking at your photos, you are indeed quite lean, and your expectations would need to be adjusted accordingly. That being said, even a small amount of transferred fat, strategically placed, often can yield favorable results — in your case, since you have overall good buttock volume and shape, fat transfer to the hip dips, and possibly the flatter buttock area if additional fat was available, would be a priority. In reviewing your photos, it does appear that there are some fatty deposits, likely from the HRT, around the umbilical area that may be usable. Often, there are some hidden deposits in the axillary region, and it looks like you may have a little there, as well. Both of these sites would experience contouring benefit from the fat removal. There appears to be some fatty deposition in the inner thighs and upper hip-lower flank areas. These deposits are actually feminizing in an attractive way when they are not excessive, and removal would be counter to your goals. Another consideration, in isolation, or as an adjunct to a BBL, is a “non-surgical BBL.” This would entail the Off-Label use of a product (meaning the product is being used outside of the FDA-approved indications, and has not been investigated and deemed safe for the altered use by the FDA), called Sculptra, in which a micronized, powdered substance, similar to the make up of a particular absorbable suture used in surgery, is injected into the deeper skin/upper soft tissue level. The body’s inflammatory response to this ultimately substance induces collagen production, which may provide limited volume and structural support. Results do take months, and repeat treatments (as well as maintenance treatments) are usually required. Regarding whether one should gain weight prior to a BBL does not have a simple answer. No doubt, additional fatty deposits would give more treatment flexibility and optimize results and volume. However, the added weight may or may not accumulate in areas most conducive to liposuction removal. For example, being genetically male, a considerable proportion of the added fat could be deposited as visceral fat, which is internal and not accessible. Also, there may a disproportionate deposition in the flanks and chest area. The flank fat would be readily accessible to liposuction, but this fat tends to be more fibrous and may be of more inferior quality for fat transfer compared to other regions. Fat deposited on the sides of the chest would be good fat for removal, but likely fat on the from of the chest would be preserved to help maintain a feminine look. The other dilemma of pre-BBL weight gain is planned post-BBL weight loss to address the undesirable fatty deposits not conducive to weight loss. Any successfully transferred fat will be responsive to weight gain and weight loss, and the subsequent loss of volume is likely. Wishes for a successor surgery and a speedy, uneventful recovery should you decide to proceed.