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How Does Fat Transfer Work?
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How Does Fat Transfer Work?

Episode 22: How Does Fat Transfer Work?

How does fat grafting work? Well, let's back up for a second and talk about what fat grafting or fat transfer actually is. So fat grafting is the process by which we harvest fat from one part of the body and use it in another part of the body. Now this is essentially a form of cellular transplantation, meaning we're taking tissue from one part of the body, in this case, it's fatty tissue or adipose cells, and repurposing it to serve a function elsewhere in the body. The difference between fat transfer and what you might classically think of as organ transplantation, like a kidney transplant or a liver transplant, is that with those operations you are taking a kidney and its blood vessel and hooking that blood vessel up to the blood vessel at the recipient site, so that blood can pump from the recipient site into the end organ, in that case the kidney.


How do fat grafts stay alive?

Whereas in a fat graft or a fat transfer, you're not hooking up any blood vessels. You're dealing with individual cells. So initially we are relying on the environment of those cells to be able to provide the same services as blood vessels. So we need those cells to get oxygen from their environment, and we need them to be able to get rid of waste products without the direct connection of a blood supply. So they do that by essentially releasing waste products into their environment and taking in the nutrients and oxygen that they need from their environment for the first several days after they're transplanted. Ultimately new blood vessels do grow into these cells and they start to function like many organ transplants once they do have an independent blood supply. So sorry for getting into the weeds there with the science, but all of this is to say that fat transfer or fat grafting is essentially a form of cellular transplantation from one part of the body to another.

What is fat grafting used for?

Fat transfer or fat grafting has had all kinds of uses. It's very popular in breast reconstruction. If we need a little more volume in the reconstructed breasts, we simply harvest fat from one part of the body and add it to the breasts to make them a little more voluminous or to improve their shape. We can use similar strategies in breast augmentation, either to enhance the appearance of a breast implant-based breast augmentation, or to do a breast augmentation with fat grafting or fat transfer on its own. Both of those things are fairly popular now. One of my favorite uses for fat grafts is in facial rejuvenation, and we can use fat to rejuvenate the face in several different ways. One of the main things that leads to the classic appearances of facial aging is the loss of facial volume. So instead of using fillers to increase facial volume and improve facial structure, we can actually use fat grafts and transfer fat from elsewhere in the body to the face to create a more youthful appearance.

We can also use fat grafting for facial rejuvenation in combination with a facelift. So where a facelift is excellent for dealing with skin laxity and we can reposition the deeper tissues of the face, there's a limit to how much volume change and volume repositioning we can do with the facelift because if you've already lost a lot of fat from your face, you can't create that fat from nowhere. Whereas with fat grafting, you have a whole new kind of flexibility. So you can reposition the facial foundation with the facelift. You can re-drape the skin to be exactly where you'd like it to be to have a nice youthful contour. But now you have this really great source of volume in the form of fat from elsewhere in the body, and we can do fat grafting at the same time as a facelift to both build that foundation and also increase facial volume, build a really nice youthful appearance.

How is fat grafting performed?

So in terms of the nitty gritty of how does fat transfer work or how does fat grafting work? We perform liposuction from what we refer to as the donor site, which is the area that we're going to grab those fat grafts from. So that's often the abdomen or the waist or the inner thigh, or anywhere with a little extra bulk that you'd like us to steal. We can often do that very gently. We don't need the power assisted liposuction for this, and we can often do it with a tiny incision, often smaller than the size of a pencil eraser so the fat is gently harvested causing almost no discomfort. We then process that fat. When I say process the fat, the goal here is to make the fat into a paste that will have a very small particle size so that it easily glides into the donor area and it can have accessibility to all those nutrients that we were talking about earlier without being caught in big clumps of fat.

We do this by passing the fat in syringes through a device that essentially exposes the fat to smaller and smaller diameter channels. So these are almost like funnels that have progressively smaller diameters. So in order to get through, the fat particles have to get smaller and smaller, and over time by doing multiple passes like this, we form that fat graft into a nice uniform, smooth paste for fat transfer into the donor site. After we've done this and we've gotten out the extra oils and other fluid that we don't necessarily want as part of our fat graft, and we do this by gently rolling the fat graft over special absorbent pads, we take that fat, load it into very small syringes, and we fit those syringes with very small diameter, fine cannulas, which are blunt tipped, and they have the lumen or the hole off to the side.

So this provides a very safe, comfortable injection experience. We then simply deposit these processed fat grafts into the recipient site. Depending on the area that we're targeting with these fat grafts, we're using extremely fine cannulas and the access points to insert these cannulas are often made with a needle. So there is really often no visible scar at all at the recipient site for a fat graft. Once that fat graft has been placed, it's essentially a waiting game.

We need to provide an optimal environment for those fat grafts, those individual fat cells or adipocytes, to be able to take on nutrients from their environment like we were speaking about earlier until new blood vessels grow to supply them directly. The key to doing this well is to, again, be using a very small fat particle size and placing only very small quantities of fat with each pass of the cannula to ensure that it's exposed to the largest surface area possible of surrounding tissue so that it can, on the one hand take in as much oxygen and nutrients as it needs, and also on the other hand, get rid of as much waste as it has to until it has its own dedicated blood supply.

How much of a fat graft will survive?

Because these fat transfers, these fat grafts are essentially cell transplants or tissue transplants, it's not guaranteed that all of the fat that we transfer is going to survive. In fact, in most cases and in most locations, we say that about 50 to 60% of the fat that we transfer on average is going to survive permanently. So in a lot of instances, we'll end up deliberately overgrafting or overfilling the recipient area so we get the result that we're looking for once that fat does partially resorb. So fat grafting is a very dynamic process. What we like to say is that by about six months after the procedure for fat transplantation or fat grafting, that's when you can really get a sense of what the final result will be like.

So no matter how much fat you're putting in, you're going to lose a percentage of it. Like we mentioned, about 40 to 50% isn't going to make it. By the time you get to about six months, you have a good sense of what that final result is going to look like. We often go into fat grafting procedures with the expectation that we're going to have to do a second round of fat transfer after six months or so, so that we have the flexibility to evaluate the result and then add a little extra fat here or there to tweak things and really get it perfect.

How does a BBL work?

I didn't mention one of the really most popular kinds of fat transfer that's done right now when I was speaking about where we're doing fat transfer a little earlier in the episode, because this kind of fat grafting really stands on its own as its own procedure. That is fat transfer to the buttocks or the Brazilian buttock lift or BBL. This is where we're taking fat from elsewhere in the body, often large volumes of fat from the abdomen or the waist or the flanks, and we're then transferring it to the buttocks. This is different because this is a very large, often, volume of fat transfer. The goal here is to improve the shape or the size of the buttocks or their projection or their perkiness. While the same principles do hold here for Brazilian buttock lift or BBL as with the other kinds of fat transfer we were discussing earlier, it deserves to be singled out and highlighted because this is a procedure that is actually a lot more dangerous than a lot of other aesthetic surgery procedures, including other kinds of fat grafting procedures, and the reasons for this aren't completely understood.

But part of the issue is that there are very large blood vessels in the buttocks and when large volumes of fat are injected into the buttocks, this can cause a fairly steep pressure gradient or put a lot of pressure on the buttocks. That can force fat into those large blood vessels in the buttocks, which can then travel to the heart and be very dangerous, even lethal in the form of what's called a fat embolism. A fat embolism is when fat gets into the circulatory system and cuts off blood supply to other parts of the body. So the Brazilian buttock lift or BBL or fat transfer to the buttocks is a unique procedure in that its risk profile is much higher than the risk for fat grafting to other parts of the body or other cosmetic surgery procedures in general. So it just deserves to be mentioned on its own. When you are considering having this procedure, it's especially important to go to a board-certified plastic surgeon who has real expertise in fat grafting and a proven safety track record, specifically with this procedure.

How much does fat grafting cost?

The other question we frequently get with regards to fat transfer is how much does fat transfer cost or how much does fat grafting costs. This is something that varies a great deal. As we've discussed with other procedures, the factors that come into play here is the experience level of your surgeon, the geography of where you're having your procedure performed, the volume of fat that you're having transferred, the location of the fat that you're having it transferred to, and the overall complexity of the procedure.

But to make things simple by way of comparison, I think it's reasonable to expect to pay in Manhattan, and that's what I'll use for reference because I have a New York City based plastic surgery practice, for a focused area of fat grafting, let's say somebody wants to use fat grafting to augment their cheeks, and the procedure is done under local anesthesia, that's something that I think you can reasonably expect to pay anywhere from $3,000 to $6,000 for, again depending on the experience level of your surgeon.

How does fat grafting of the breasts work?

Another area that I'd like to touch on specifically here is fat grafting of the breasts. This is a topic that requires special mention because the breasts obviously are usually a paired structure, meaning you have a right breast and a left breast. We've previously mentioned that we don't know for sure how much fat is going to survive with a given fat grafting procedure. So if we're using fat to augment the breasts, it follows that we can't be sure that even if we put the same amount of fat on both sides, we're going to have the same amount of fat permanently survive in each breast.

So to make sure we get good symmetry, you really need to go into one of these fat grafting procedures to the breasts with an open mind to having a secondary fat grafting procedure. The other thing to know about fat grafting to the breast is that, while it's very appealing in a lot of ways to look at fat grafting as a primary way to do a breast augmentation, maybe you don't need a breast implant if you're using fat, it really takes a significant amount of fat to increase your breast size as much as you might like to. So as a framework for reference, we usually say that to increase the breasts by a cup size, you have to increase the volume of the breast by 100 to 150 ccs or milliliters. That is a significant amount of fat. For example, in a standard liposuction case of the abdomen, I'm usually taking between 600 ccs or milliliters and a liter of fat from the abdomen.

After processing, about half of that fat is actually useful for transplantation. So if we're taking at most a liter of fat out of the abdomen during a liposuction procedure, we're going to have about 500 ccs or 500 milliliters of usable fat for fat grafting. Assuming we're going to be grafting the breasts pretty much symmetrically that gives us 250 ccs or 250 milliliters per side of fat. And then if we remember that we said that about half of that fat on average is going to last in a permanent way, that means that just 125 ccs of fat is going to last in a meaningful way. So in a standard liposuction case where we're taking a significant volume of fat from the abdomen, that's about a liter, we're going to end up with about 125 ccs of fat that's going to stick around on each side.

If you recall on average that to go up an entire cup size, we need between 100 and 150 ccs of fat, that means that for this fat grafting procedure where we're taking a fairly hefty amount of fat from the stomach, a whole liter, we're only going to be able to go up a cup size. So again, the fat transfer method when used in isolation for breast augmentation might be okay for those that want a modest improvement. But if you're looking to go up significantly in your breast size, for the most part you should really be looking at an implant-based breast augmentation, which can certainly be augmented by a fat graft if you want to manipulate specific aspects of the breast shape. For example, sometimes people will have an implant-based breast augmentation and then have fat grafting to the upper pole of their breasts to really highlight that fullness, but fat transfer on its own may not be the best approach to a breast augmentation if you're looking for a really large increase in breast volume.


So there you have it. That is more or less the skinny on fat transfer or fat grafting. We hope that that's explained how fat grafting works, specifically fat grafting for breast augmentation and fat grafting for facial rejuvenation or facial volume, and also fat grafting to the buttocks in the form of a Brazilian buttock lift. So fat grafting is a very powerful procedure, but we really have to understand the nuances to make sure that we're delivering the optimal results that you want to be seeing.


  • Darren M. Smith MD
  • Darren M. Smith MD
  • Darren M. Smith MD

All photos are of models except before and after images.

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