Key Point

• Long ignored or thought of as packing material filling the space between skin and muscles, fat is finally getting its recognition as essential to human health and a part of the fascial system massage therapists tend to every day.

Our culture has a big “fat problem,” and it’s not the global obesity epidemic. Fat is among the body’s most vilified and ignored tissues. Yet, as bodyworkers, it’s one of the tissues we manipulate the most in our clients, regardless of body size. Whether you use more superficial modalities or your intentions run to deeper tissues, fat is right under your hands in every massage. But how much have you been taught about fat as a tissue? Probably not a lot, which is understandable, because a lot is still being discovered about it. Research from the past few decades is rewriting the story of fat tissue as a major endocrine organ, essential to human health, and a fascinating part of the fascial system that we massage every day. It’s time for a reintroduction to fat—welcome to Fat 101.

The “Fat Problem”

When fat is given attention, its importance is summarily reduced to this question: How much fat is there? And that’s frequently followed up with: How do we get rid of it? This disavowal permeates every level of our culture and has dangerously made its way into health care. While weight bias among medical professionals is starting to get some long-overdue attention, the problem runs deeper than clinical interactions—so deep that it’s embedded in our understanding of fat tissue itself in human anatomy and physiology.¹

A recent study on weight stigma in medical training offers a glimpse into how this is playing out in medical school anatomy labs. In one setting, medical students routinely complained about “difficult,” larger-sized donor bodies (cadavers). The students resented dealing with all the fat before—in their words—“getting to the real anatomy.”² It’s tempting to shake our heads at the weight bias running rampant in these anatomy classes, but the reports reveal another bias that goes beyond size—an accompanying fat bias shaped their views about what tissues count as “real” anatomy. What does “real anatomy” even mean? Clearly, fat didn’t make the list.

What happens, though, if we shift the focus and put aside our culture’s insidious obsession with “how much fat” and instead get curious about fat as normal and essential anatomy in all bodies? As it turns out, fat is fascinating, dynamic, and complex.

Curious Massage Therapists

What would it be like to encounter fat in the dissection lab, in a setting where curiosity can flow—with no pressure of exams, no preset curriculum, ample time to explore, and from the perspective of massage therapists?

Let’s imagine for a moment that we’ve joined a group of curious massage therapists in the dissection lab. Carefully observing, we make our way through the skin’s epidermis and dermis. Passing through the skin, bright yellow fat tissue appears. Full of plump, round lobules, the fat is striking in color and distinct from the densely packed dermis above and the tougher fascia below. While many of us haven’t seen fat lobules uncovered, their texture is perhaps familiar to us as the dimpling of cellulite on our—or our clients’—bodies.

As this sea of yellow comes into view, we reflect on how those medical students wanted to get past the fat to the “real anatomy.” Fat is easy to dismiss as a bunch of blobs, while the muscles and deep fascia beckon to us from below. But when we pause and get curious as massage therapists, new questions come up: What happens to the fat when we put pressure on it, squeeze it, and massage it? How does the fat move under our hands? Can we feel its texture through the skin? How do we access deeper tissues through the fat? Does the fat make muscles feel softer or bigger than they really are?

Perhaps more foundational questions would emerge: What is fat, really? And what’s it doing here
under the skin? 

Physiology: What Is Fat?

Although we talk about fat like it’s one thing, fats are an entire category of biological molecules, also known by
the technical term lipids. The role of these fat molecules
is essential. 

Fats: Essential Molecules

Fats encompass a broad range of biological substances, including our massage oils and familiar dietary fats such as olive oil, coconut oil, and butter. While they got a bad rap in the low-fat diet craze of the 1980s, fats are essential parts of human physiology. They serve as the foundation of important hormones, including estrogen, testosterone, and cortisol. They allow for the absorption and transport of fat-soluble vitamins, such as vitamins A, D, E, and K. They even create the nervous system’s insulating myelin sheath and form the cell membrane of every one of the trillions of cells in the body.

Energy Storage: It’s Essential

Fat molecules play another familiar physiological role—energy storage. When we eat extra energy (calories), the body saves some for later in the form of fat molecules. This is a remarkably efficient way of storing energy. Most organisms, even insects and trees, use some type of fat-storage mechanism, ensuring an energy source even when food is scarce. 

Though humans aren’t the only organisms that use fats for energy reserves, we are one of the best at it. Fat is so critical to human survival that by just 14 weeks gestation, we are already storing fat—earlier than most mammals. This is well before many other systems in the body are up and running. Baby fat is more than cute; it’s essential.³

Adipocytes: Cellular Fat Managers

Energy-storing fat molecules are housed in specialized cells called adipocytes. These cells each contain a large droplet of fat molecules that takes up most of the inside of the cell. The fat droplet is like an energy savings account; we can add or withdraw fat molecules from it on a daily basis. Each of us is born with a starter set of about 5 billion fat cells, growing that number to perhaps 20 to 40 billion by adulthood. As we gain additional body fat, our fat tissue expands by first increasing the size of our fat cells (i.e., by storing more fat molecules in each cell) and then by adding new fat cells. 

Adipokines: Fat is Busy 

For most of the last century, adipocytes were seen as an inert and passive place to store our energy reserves. Eat some extra calories and the body will store them in fat cells until needed—end of story. About 30 years ago, this narrative completely changed. Working with a new strain of severely obese mice, scientists realized these mice were missing a protein normally circulating in the systems of other mice.⁴ The discovery of this protein initiated an avalanche of further discoveries of similar molecules, now known as adipokines. Produced and secreted by the fat cells themselves, adipokines were communicating with cells throughout the body—with the liver, muscles, bones, and even the brain. This discovery was a game changer in the fat story. Not passive at all, fat was actively and dynamically involved in critical metabolic processes such as food intake, insulin sensitivity, and insulin secretion. 

Endocrine Organ 

Because of these recent discoveries, fat tissue has been redefined as an endocrine organ and a central player in human metabolism and energy homeostasis. Accordingly, in many research circles, the obesity conversation is being reframed. The focus is shifting from “getting rid of fat” to instead defining the features of healthy versus diseased fat tissue. Many researchers argue that larger fat reserves are not, in and of themselves, in a diseased state; health problems arise when fat’s endocrine function is compromised.⁵

While the dynamic adipocyte is the star of the show for the research community, massage therapists don’t touch individual fat cells; we touch tissues. Let’s zoom out to the tissue level to understand more about the fat we massage. 

Anatomy: Where Is Fat Tissue Found?

Fat is found throughout the body, both in places we can and cannot reach with our massage. When fat cells have a particularly big job to do, they are organized into fat tissue, a type of connective tissue also known as adipose. 

Fat Pads

In specific regions, adipose is packed together as fat pads. Some of our most important organs have their own cushioning and insulating fat pads, including the heart (epicardial fat pad) and kidneys (renal fat pads). High-impact regions such as the knees (infrapatellar fat pads) and the soles of the feet (plantar fat pads) are also reinforced with adipose, as are the sensitive palms and fingertips we use to give massage.

Neurovascular Cushions

Fat can be a signal in the dissection lab that you’re approaching an important structure. Neurovascular bundles travel through our tissue in clouds of protective fat so that if you sink in over them with compression, they are sheltered from your pressure in a nest of cushioning adipose. Because of the functional and protective role of cushions and fat pads, they are not first in line when the body needs to tap into its fat reserves for energy; the body has designated storage zones for that. 

Fat Depots

The body’s larger energy reserves are extensively distributed in expanses of adipose tissue called “fat depots.” Depots? Yes, fat has storage depots, just like trains, office supplies, and home improvement tools. In humans, there are two major fat depots—subcutaneous fat (storing fat under the skin) and visceral fat (storing fat around the organs). Together, these depots serve as the physical storage warehouses of the body’s energy reserves. The subcutaneous fat depot, or subcutis, is of particular interest to us as massage therapists—not because of its fat-storing role, but because it’s the fat we feel when we massage.

The Subcutis Zone

The subcutis is continuous under the skin, everywhere on the body. While some areas are more familiar than others (such as the abdomen and over the glutes), you’ll also find this fat tissue under the skin on the nose, the sole of the foot, the elbow, and even the scalp. Beyond housing our fat reserves, the subcutis is a vibrant zone that plays both important physiological and mechanical roles. It supports our skin and creates a buffer separating the external surface from the deeper layers. Richly innervated and highly vascularized, it serves as a major communication hub and provides extensive pathways to lymph vessels. 

All these jobs are made possible because of how the subcutaneous fat is organized as a tissue. A fibrous support network runs throughout the subcutis zone. Without this structural organization, fat would have no stability for functioning; the simple act of leaning against a door frame or the squeezing action of a massage stroke would push the fat cells from one place to another and significantly distort our tissues. Fat can’t do its job alone; it depends on its structural framework.

New Paradigm: Superficial Fascia

The fibrous support network of subcutaneous fat gained the attention of researchers who turned to technology to zoom in closer. High-definition ultrasound and microscopes brought the support network prominently into view and revealed its organization all over the human body. What did researchers see? Fascia. Careful examination revealed a honeycomb-like, three-dimensional, collagen-based fascial network surrounding every fat lobule and reaching from the skin down to the deeper layers.⁶ With this new perspective, fascia researchers reframed the subcutis as a fascial layer and part of the human fascial system (Image 3). This structural organization transforms the energy-storing fat of the subcutis into a multitasking tissue. Within its collagenous frame, the supported fat creates the protective cushioning that massage therapists encounter with every stroke. 

A Different Type of Fascia

While the subcutis looks like one uniform layer of fat, it is really two distinct fat layers loosely divided by a fibrous membrane: the superficial fascia (Image 4). This is not the same fascia that wraps around every muscle, nor is it the same force-transmitting fascia that creates the IT band and thoracolumbar fascia. That’s the deep fascia that works as a unit with our muscular system. This lesser-known superficial fascia creates a functional unit of our skin with the subcutaneous fat. It organizes our fat to create a vibrant, active zone that supports all the subcutis’ physiological and mechanical jobs. And it helps explain how the subcutis moves with the skin under our hands
in massage.

Sliding Layers, Anchored Layers

However, the subcutis doesn’t always move as one unit under our hands.⁷ The layers have some strategic, built-in gliding capacity between them. A shearing massage stroke might move the skin and cushiony fat but glide right over the deeper tissues. Why would the tissue be organized this way? Movement. To accommodate our moving bodies, the superficial and deeper tissues need to move somewhat independently from one another. If not, movement would be awkward, limited, and painful, with the skin and muscles pulling on each other. Engaged effleurage, petrissage, and even skin rolling rely on this subcutis gliding capacity.

Our subcutis layers aren’t always organized to promote gliding between layers. In some regions, they are anchored for stability. In these areas, minimal fat can accumulate, and the superficial fascia membrane adheres strongly to the deep fascia below. This creates an anchored “no-glide zone” in areas like the palms of our hands or along the body’s midline.

Emerging Questions

Reframing the subcutis as a fascial layer is key as we start to understand just how important it is for massage therapists to understand fat tissue. It shifts our attention from the amount of fat to the fibrous honeycomb network organizing it, raising so many questions: What role does the superficial fascia play in health? In pathologies? Can we change it with our hands? Is it innervated? Might it be involved in our clients’ experiences of pain? 

New research is emerging on many of these fronts. Let’s turn our attention to a few that have particular relevance to massage therapy: innervation and scar tissue.

Fat Can Feel: Innervation

Some of us are a little sensitive about our body fat, but as it turns out, our subcutaneous fat is pretty sensitive itself. Recent studies have found that the fascial layer under the skin is one of the most innervated tissues in the body. This is a big deal, considering that our subcutis fat layer was traditionally assumed to be just a bunch of packing material filling in the space between the skin and muscles. Knowing that a particular tissue is innervated confirms it’s not inactive or passive. Quite to the contrary, that tissue is actively communicating with the rest of the body via the nervous system.

Ranking No. 2 in Sensitivity: While most of the earlier findings on fascial innervation have been about the deep fascia, the new details on the subcutis are expanding the full fascia innervation story.⁸ Wanting to understand pain better following hip surgeries, a group of researchers compared the innervation of multiple tissues injured during these surgeries from the skin at the surface to as deep as a joint capsule. Not surprisingly, the skin was the most innervated. What was surprising, though, was that the second-most innervated tissue was not the muscles nor the deep fascia but the same superficial fascia that organizes the subcutaneous fat. With this new information, they zoomed in specifically on the superficial fascia and confirmed its extensive level of innervation.⁹

Fight-or-Flight Fat: While the physical presence of nerves is part of the story, the type of nerves fills in more details. A significant concentration of nerves in the superficial fascia are from the sympathetic nervous system—the system controlling the fight-or-flight stress response. Some of these nerves control the extensive blood network, but not all of them, prompting researchers to ask if chronic stress might impact our subcutis. 

Sensitive Fat: Significantly, research also found sensory nerves in the form of free nerve endings known to respond to temperature and mechanical stimulation and gather information on potential tissue damage. These findings suggest the superficial fascia and subcutaneous fat could play a role in nociception. Researchers are curious if this helps explain why scars can be more painful when the subcutaneous tissues are also injured.

Respect the Fat: What do these findings mean for us as massage therapists? Fat needs to be respected as a sensitive tissue. It’s not inert and it’s not extra. The presence of nociceptors in the subcutis opens the possibility that these tissues can be involved in the pain our clients are experiencing. Even if the subcutaneous layer is not our target tissue, we should be mindful that important sensory information could be coming from the fat layer itself. 

Fat Can Heal: Scar Tissue

As massage therapists, we meet a scar at the skin’s surface, but our hands know that scars can have immense depth, continuous through the layers of the subcutaneous fat beneath (Image 5). As the subcutis is reframed as a fascial layer, new conversations are opening about its role in scar formation. It turns out that scarring doesn’t just happen to the fat layer; the fat layer might actually be driving scar formation. 

Driving the Healing Process: Recent evidence indicates that in wounds deeper than the skin’s dermis, fibroblasts from the superficial fascia rise to the surface to build the scar.¹⁰ Dragging along the superficial fascia with its nerves, macrophages, and blood vessels, these fibroblasts create a “patch” for the wound that serves as a scaffold for the newly forming scar. Exploring this mechanism in mice, researchers found that when the superficial fascia was removed from an injured area, wounds did not heal at all.¹¹

While these new findings don’t offer us new treatments, they do affirm what our hands feel: The scar we see at the surface is often just the tip of the iceberg. It can be helpful to reframe our exploration of that deeper scar tissue as a disruption in the multilayered honeycomb network of the subcutis, better guiding our hands as we explore these changes beneath the surface. 

Changes in the Network

Scar tissue is not the only change in the subcutis we can feel with our hands. Aging, gravity, weight gain, and weight loss all put strains on the fibrous network, and sometimes we can feel this in our clients’ tissue.

Changes Over Time

As we age, our overall subcutis may feel softer and more lax because of changes to the fibrous network, regardless of the actual amount of fat reserves. Just as the skin’s dermis loses elasticity as we age, so can the honeycomb network that supports our subcutaneous fat. While aging might bring laxity, the fibrous network can also become more fibrotic and reinforced with changes that accompany injuries, surgeries, medications, and some pathologies, including diabetes.

Cellulite: It’s Not All Fat

Cellulite is a familiar and benign dimpling appearance of the skin’s surface. While it offers a masked glimpse of the fat lobules below, cellulite is not simply fat; it’s a reflection of the relationships between the skin, fat lobules, and the honeycomb fibrous network. The dimpling appears when either fat lobules press up against the dermis or the fibrous network more strongly tethers the dermis down around the fat lobules. Increased fat lobule size (weight gain), increased interstitial fluid (edema), or changes to the fibrous honeycomb network can all create the dimpling appearance. Cellulite also can appear over time as the normal aging of the skin’s dermis reveals the underlying structure of the fibrous network and fat lobules below, even in people with an unchanging body-fat composition. 

Adipose Disorders: When Fat Hurts

When changes in the subcutaneous fat can only be conceptualized as excess fat, people with adipose disorders like lipedema and Dercum’s disease suffer and spend years searching for answers.¹² Both these adipose disorders are grossly underdiagnosed and regularly dismissed as obesity. Yet, no amount of dieting or exercise reduces the fat deposits in these conditions. Primarily affecting women, lipedema is characterized by an abnormal buildup and distribution of subcutaneous fat and fluid, often disproportionately in the limbs; as it progresses, it can be increasingly painful and disfiguring to the point of affecting daily activities. Dercum’s disease results in palpable, nodular subcutaneous lipomas that can continue to grow into painful masses. Both these diseases are progressive, and although there is no cure, there are treatment options, including manual therapy. Massage therapists who specialize in lymphatics provide relief by addressing the nonfat elements of the subcutis. 

What’s Next for Fat?

The rewriting of the sensitive, soft, fatty, fibrous, scar-making fascial layer under our skin is still unfolding as new research continuously adds more to the story. What is already certain is that for our hands as massage therapists, the quantity of a client’s body fat is just one detail, and perhaps not even the most interesting one.

Massage therapists are making great strides in drawing attention to weight bias and creating body-positive and size-inclusive practices. The next step is bringing fat tissue into our anatomy education and reframing it as normal and essential tissue in all bodies. While this should be important to all practitioners working with the human body, it’s particularly important to us as massage therapists, given how much fat influences our palpation of the deeper tissue below.

There might be something more personal at play for all of us. Remember our medical students who wanted to get past the fat to the “real” anatomy? The study also found that these students’ self-image worsened by the time they had completed the class. Several had started diets and were making disparaging comments about their bodies. As we reframe how we teach, study, and massage the fat tissue in our clients, we are also signaling to our students, colleagues, and ourselves that even our own body fat is normal and essential tissue worthy of being massaged. If you are curious about fat, find a dissection lab experience that supports curious massage therapists. 

Notes

1. Aaron M. Cypess, “Reassessing Human Adipose Tissue,” New England Journal of Medicine 386, no.  8 (2022): 768–79, https://doi.org/10.1056/nejmra2032804; Evan D. Rosen and Bruce. M. Spiegelman, “What We Talk About When We Talk About Fat,” Cell 156, nos. 1-2 (January 2014): 20–44, https://doi.org/10.1016/j.cell.2013.12.012.

2. Adeline L. Goss et al., “The ‘Difficult’ Cadaver: Weight Bias in the Gross Anatomy Lab,” Medical Education Online 25, no. 1 (March 2020): https://doi.org/10.1080/10872981.2020.1742966; Kevin Patton, “Weight Stigma! The Difficult Cadaver—Journal Club,” May 17, 2021, in The A&P Professor, episode 93, https://theapprofessor.org/podcast-episode-93.html.

3. For a fascinating exploration of the evolutionary history of human fat, see Daniel Lieberman, The Story of the Human Body: Evolution, Health, and Disease (New York: Vintage Books, 2014). For more on different types of fat tissue, including white, brown, and beige, see Paul Cohen and Bruce M. Spiegelman, “Cell Biology of Fat Storage,” Molecular Biology of the Cell 27, no. 16 (August 2016): 2519–631, https://doi.org/10.1091/mbc.e15-10-0749, and Rachel K. Zwick et al., “Anatomical, Physiological, and Functional Diversity of Adipose Tissue,” Cell Metabolism 27, no. 1 (January 2018): 68–83, https://doi.org/10.1016/j.cmet.2017.12.002.

4. Leptin was the first discovered and named adipokine. For a history of the discovery of adipokines, see Philipp E. Scherer, “The Many Secret Lives of Adipocytes: Implications for Diabetes,” Diabetologia 62, no. 2 (February 2019): 223–32, https://doi.org/10.1007/s00125-018-4777-x;  Aaron M. Cypess, “Reassessing Human Adipose Tissue.” 

5. Scherer, “The Many Secret Lives of Adipocytes: Implications for Diabetes;” Rosen and Spiegelman, “What We Talk About When We Talk About Fat.”

6. For the most comprehensive exploration of the subcutis as a fascial layer, see Carla Stecco, Functional Atlas of the Human Fascial System (Edinburgh: Churchill Livingstone Elsevier, 2015), and M. F.  Abu-Hijleh et al., “The Membranous Layer of Superficial Fascia: Evidence for Its Widespread Distribution in the Body,” Surgical and Radiologic Anatomy 28, no. 6 (December 2006): 606–19, https://doi.org/10.1007/s00276-006-0142-8.

7. For a deeper look at the sliding and anchoring of the subcutis, see Carla Stecco, Functional Atlas of the Human Fascial System; Luca Lancerotto et al., “Layers of the Abdominal Wall: Anatomical Investigation of Subcutaneous Tissue and Superficial Fascia,” Surgical and Radiologic Anatomy 33, no. 10 (December 2011): 835–42, https://doi.org/10.1007/s00276-010-0772-8.

8. Caterina Fede et al., “Fascia and Soft Tissues Innervation in the Human Hip and Their Possible Role in Post‐Surgical Pain,” Journal of Orthopaedic Research 38, no. 7 (July 2020): 1646–54, https://doi.org/10.1002/jor.24665.

9. Caterina Fede et al., “Innervation of Human Superficial Fascia,” Frontiers in Neuroanatomy 16 (August 2022): 981426, https://doi.org/10.3389/fnana.2022.981426.

10. Dongsheng Jiang and Yuval Rinkevich, “Furnishing Wound Repair by the Subcutaneous Fascia,” International Journal of Molecular Sciences 22, no. 16 (August 2021): 9006. https://doi.org/10.3390/ijms22169006.

11. Donovan Correa-Gallegos et al., “Patch Repair of Deep Wounds by Mobilized Fascia,” Nature 576, no. 7787 (December 2019): 287–92, https://doi.org/10.1038/s41586-019-1794-y.

12. K. Beltran and K. L. Herbst, “Differentiating Lipedema and Dercum’s Disease,” International Journal of Obesity 41, no. 2 (February 2017): 240–45. https://doi.org/10.1038/ijo.2016.205.

The Subcutis in Cross Section

Looking at the subcutis in cross section helps us understand both the individual parts and see how each layer is interconnected from the skin through the fat all the way to the deep fascia.

Honeycomb Network (A)

Tiny bands of connective tissue known as skin ligaments dynamically anchor the skin to the tissues below. Skin ligaments create compartments that encase each fat lobule, ensuring that our fat reserves are not floating around under the skin. Together with the superficial fascia membrane, they form the three-dimensional honeycomb network that interconnects all the subcutis layers. 

SAT: Fat that Cushions (B)

The fat layer closest to the skin is the superficial adipose tissue (SAT). Strongly connected to the dermis, it’s highly organized, with well-formed, rounded fat lobules. Mechanically, it offers cushioning every time we bump up against a table and when we spend the afternoon sitting. For bodyworkers, it enhances the softness we feel under our hands in our clients’ tissues. It’s what moves with the skin in every effleurage stroke. 

The Superficial Fascia   Membrane (C)

The membranous superficial fascia divides the two layers of fat. This fibroelastic tissue manages much of the tissue tension in the subcutis. It’s organized to absorb and disperse mechanical loads coming from multiple directions. Running in a plane parallel to the skin, it provides stability and anchoring to the surrounding tissues, including vasculature, nerves, and lymph vessels.

DAT: Fat That Glides (D)

The deep adipose tissue (DAT) is nestled between the superficial fascia and the deep fascia. Much less structured, the lobules are often elongated and oval-shaped; sometimes, they don’t even look like lobules. The DAT’s fibrous element is frequently more loosely arranged, which supports an important job: gliding. Rich in hydrated, loose connective tissue, DAT creates a slippery, gliding surface between the subcutis and the musculoskeletal system. To our hands as massage therapists, DAT is not as easy to palpate as SAT, but our hands know it is there when the subcutis easily glides in relation to the deeper layers.