Other than skin, fat is the most commonly manipulated tissue by plastic surgeons. Most people think of fat removal by liposuction when they think of plastic surgery by fat transplantation by injection is becoming increasingly popular. But when fat cells are removed or transplanted the questions are whether they will come back or do they survive and grow? The basic science of fat cell biology helps answer these questions.
Fat cells are created during the last three months of pregnancy and during puberty and are influenced by the estrogen and testosterone hormones. The development of fat cells and their distribution are the same in male and females until puberty when the surge in hormones changes their bodily distributions. After puberty, fat cells do not generally replicate or are created (fat cell hyperplasia) and their number remains fairly stable for the rest of one’s life. One may get heavier or get bigger in certain body areas because fat cells gets bigger taking on excess calories. (fat cell hypertrophy) This is best illustrated as to what happens in the bariatric surgery patient where extreme amounts of weight loss occur…their fat cells merely get smaller but not less in number.
Liposuction removes fat cells but leaves many fat cells behind. No liposuction treated area removes all the fat cells. If one gains weight after liposuction, those remaining fat cells can get bigger. Thus one cal potentially wipe out any body contouring benefits from the procedure. When fat cells are transplanted, those that survive have the same characteristics from whence they came which is usually the stomach area. With weight gain those transplanted fat cells can get bigger or with weight loss those same fat cells can get smaller. Thus fat injected areas can grow or get smaller after transplantation.
Fat cells are well known to release a large of cytokines (adipokines) that help regulate energy homeostasis and overall body fat mass. (leptin, tumor necrosis factor and many others) Leptin, for example, is a hormone produced by fat cells to help regulate body energy balance. Higher levels of leptin release favors energy burning rather than storage. Bigger fat cells release higher amounts of leptin than smaller fat cells which tell the brain to have one stop eating and burn more energy. But in the obese patient their brain is more resistant to this leptin message and is one reason they may continue to gain weight or can’t keep it off.
Conversely, smaller fat cells send out very low levels of leptin telling the brain to store energy rather than use it. This simplistic hormonal science would lend support to the fat cell homeostasis concept which in the liposuction patient could mean that removing large amounts of fat cells and mass, with resultant less circulating leptin, may be inadvertently inducing the body to try and put the fat back. However, whether the brain/body responds to fat cell number loss by increasing preadipocyte conversion and/or differentation in an attempt to maintain the fat mass it had is still a theoretical response.
While these fat cell behavior concepts seem straightforward and a bit contradictory, the variability of body type and fat mass must surely play a role in how these body fat responses are played out. If one divides body types into five main groups (lean, average, overweight, obese, extremely obese), it is clear that a change in body type is associated with a similar change in fat cellularity. (one who is obese has bigger fat cells than one who is lean and most likely has more fat cells as well) Research has clearly shown that obesity presents with different types of cell changes with severe obesity having increased numbers of fats as well as a fat cell size problem.
This would intuitively seem to change the dynamics of fat mass equilibrium in lean vs obese individuals even though their cell turnover rates may be the same. It just simply harder to keep fat off the more fat mass one has. This would also lend credence to why ‘liposuction is not a weight loss method but a spot reduction technique.’ Liposuction just simply does not work well in overweight or the obese individual. Not because it often doesn’t make much of a visible difference (which it often won’t in an obese individual) but that the fat has a much greater propensity to hypertrophy or even be induced to make new cells due to the stimulation of the traumatic fat injury and loss. In essence, liposuction in obesity appears to be metabolically challenged or even doomed. As unfair as it may be, liposuction in leaner body types is not only more visibly rewarding but may be more sustainable long-term as well provided that a good energy balance is maintained.
While subcutaneous fat makes up about 80% of all body fat, it is suspected that it is not all the same. The fat around the abdomen and waistline is clearly more of a depot type fat than that of the neck or knees for example. (metabolic diversity) Fat accumulations occur in the abdomen either first or preferably in unfavorable energy balances. (the visceral intra-abdominal fat aside) Whether this is due to a greater number of fat cells per cm2 of tissue or a greater susceptibility to be stimulated for volume acquisition by increased receptors, or both, is not known. Such localized fat mass differences may account for why ‘liposuction may be more sustainable in some body areas than others’ once the cell numbers are decreased. For example, once the inner knees are reduced even in an obese patient, it is unusual to ever see much if any accumulation later. Certainly the same can not be said for subcutaneous abdominal fat removal.
In search of addressing the simple question of whether fat will return after liposuction…our current understanding of fat cell biology does not permit a clear biologic answer. That may not be satisfying to a prospective patient but is reflective of what we currently know. Current fat cell science suggests that:
Liposuction should not be viewed as a permanent or lifelong body contouring procedure. One may or may not get years of aesthetic benefit from localized removal of fat but the factors contributing to its long-term sustainability are not yet known.
It is sound biologic advice to maintain one’s weight after liposuction. This is the best way to prevent a subsequent increase in fat cell volume.
Liposuction works best in near weight appropriate individuals both in visible changes and in a greater likelihood of a sustained result. When a plastic surgeon tells a patient to lose some weight (or be within 20% of less of their ideal body weight) before being a good candidate for liposuction, that advice has some biologic merit and is in the patient’s best interest.
Obese individuals appear to be a biologic setup for a complete relapse for fat re-accumulation, most likely quicker than in a lean or weight appropriate individual.
Fat reaccumulation after liposuction, when and if it does occur, may develop from whence it was removed or may have tendency to occur elsewhere. This appears to vary by the individual. It is does not exclusively occur one way or the other and there is no scientific evidence that it does.
Much of body contouring surgery employs well known methods of liposuction whose effectiveness is based on the removal of fat cells and their lipid contents. While lipoaspiration is highly successful in the short-term, as evidenced by endless before and after pictures from plastic surgeons, patients understandably want to know what is it’s long-term effects. In short, are the fat reduction results sustained and will the fat come back?
In reality, the long-term effects of liposuction in terms of sustainability has not really been studied in any prospective controlled manner. Much of what is said about this issue is based largely on anectodal observations as well as numerous unfounded truths or myths that are propagated amidst the general public. (not to mention doctors as well) Suffice it to say that studying fat and body mass behavior is difficult due to many variables such as genetic make-up, environment influences and lifestyle. There are few if any truly homogenous liposuction patients other than that they have all agreed to undergo the surgery.
But the biology of fat cells and what happens to them over one’s lifetime has been extensively researched and new insights into their behavior have been gained in the past decade. Granted much of this fat work has been done from the perspective of obesity and not liposuction per se. But what can be gleaned from fat biology research that may at least partially address what may happen after liposuction?
There is an historic belief that you are born with a certain number of fat cells and they remain constant throughout life. I have heard this said many times, even from plastic surgeons, and this perception undoubtably serves as the basis for the belief that ‘once liposuction removes fat cells they can not come back’. (implying a permanency to the procedure) The reality is that this statement is both true and false. The number of fat cells increases up through puberty but actually remains relatively constant throughout adult life. This is supported by numerous studies that have demonstrated that after weight loss over months to years fat cell volume decreases but fat cell number remains constant. Even in cancer cachexia severe volume depletion occurs but not cell number. Conversely, significant weight gain results in an increase in fat cell volume but not number. Thus weight gain in adulthood is primarily the result of changes in fat cell volume.
Once could thus conclude that at some point in one’s development the final fat cell number is established and no further fat cell activity occurs. However, this static viewpoint of the fat cell population is incorrect. Fat cells are now known to be a very dynamic tissue that is far from a mere quiescent depot of lipids. They are a highly regulated cell population that undergoes significant turnover. Old adipocytes are constantly replaced by new ones such that it has been estimated that half of all fat cells are replaced every eight years or so in humans. (roughly 10% cell renewal every year) These replacements come from the progenitor cells (preadipocytes) in the stromal vascular fraction of fatty tissue.
How this process is regulated is not precisely known but it appears that these preadipocytes are stimulated to become an actual fat cell to keep pace with those fat cells that are dying, thus keeping fat mass in constant flux but the fat cell numbers constant. This fat cell homestasis effect gives potential credence to a contrarian liposuction effect that ‘whatever fat cells are removed will be replaced and the fat removed will eventually return’. Whether it returns to the same place from whence it came or accumulates elsewhere is an extension of that viewpoint.
These initial fat cell biology concepts pose completely opposite views about the long-term effects of liposuction. Much clinical evidence, an even that from patients, favors more of the fat mass homeostasis effect of which the surgical reduction in fat cell numbers can be overwhelmed by eventual fat cell volume hypertrophy.
Dr. Barry Eppley is an extensively trained plastic and cosmetic surgeon with more than 20 years of surgical experience. He is both a licensed physician and dentist as well as double board-certified in both Plastic and Reconstructive Surgery and Oral and Maxillofacial Surgery. This training allows him to perform the most complex surgical procedures from cosmetic changes to the face and body to craniofacial surgery. Dr. Eppley has made extensive contributions to plastic surgery starting with the development of several advanced surgical techniques. He is a revered author, lecturer and educator in the field of plastic and cosmetic surgery.