Fat & all its Facets
In 2022, the New England Journal of Medicine published a review article titled “Reassessing Human Adipose Tissue.” They begin with:
Adipose tissue is an underappreciated and misunderstood organ…. Too many people are confident that they know what fat is: an undesired body appendage that they strive to reduce over their entire lives. For those who struggle to lose weight, fat is often a source of misery, not marvel. Among medical professionals, it had been disregarded to the extent that fat has merited little attention in curricula and does not even feature in atlases of anatomy. Fortunately, the past three decades have witnessed a revolution in our understanding of and perspective on this tissue.
Fat, also called “adipose tissue,” has made the naughty list for far too long. At best it’s treated as a fuel storage organ, at worst it’s treated as a lifelong nemesis, and hardly ever treated like the fundamental endocrine organ that it is. It’s time we, doctors and patients alike, start thinking and talking about adipose tissue like we do all other organs which serve a function. We wouldn’t call the thyroid a “bad” organ, but we also work to make sure it’s not under or over-functioning. Adipose tissue is an organ to be nourished, supported, and sometimes balanced.
In this blog, we’ll dive into what composes adipose tissue, the differences between the two major types, the functionality of this complex organ, how optimal health includes having healthy fat tissue, and what that might entail.
Fats or “lipids” are a type of macromolecule that is composed of fatty acids. Lipids contain a lot of energy within them. Organisms of all kinds require lipids for different functions, but at the core, lipids simply make for a great fuel to store for future energy needs. In humans, lipids are stored in big sacs within adipose cells. Each adipose cell contains one fat sac, and that fat sac can grow according to how much is being stored within it.
Fat as a tissue, called “adipose tissue,” goes beyond just the adipose cells. It contains blood vessels, immune system cells, and precursor cells.
White adipose tissue
Adipose tissue comes in two major types–white adipose tissue (WAT) and brown adipose tissue (BAT). WAT is the form that stores extra calories for later energy use and has two categories of location. One location is when WAT surrounds our vital organs, called “visceral fat,” and the other location is when it is located just below our skin layer, called “subcutaneous fat.” In both of these locations, WAT’s role is to store energy as fat, or triglycerides, to be used as fuel for nearby cells. This is how WAT gets its name, it appears light in color due to what it mostly contains. WAT also acts to retain heat and insulate our bodies & organs and be a physical protective barrier to whatever it surrounds.
Brown adipose tissue
BAT gets its name because instead of primarily containing stored fat, it contains tons of mitochondria–the powerhouse of the cell. This clues us in that BAT is an extremely metabolically active tissue, and it turns out that BAT acts as a sort of furnace for the human body. BAT still stores fat though–that’s the fuel that it’s burning. BAT’s activity can put a fire (figuratively speaking, as the furnace that it is) under our metabolism’s butt, kicking it up a notch to burn more stored fuel.
Infants are born with more brown fat, percentage-wise, as it helps to warm the tiny, new bodies. In adults, BAT is only found in very specific and limited areas–in the neck, along the chest cavity, and in the abdomen close to the kidneys. In comparison to WAT, where WAT comprises 30-40% of total body mass in women and 15-25% in men, BAT makes up 0.1-0.5% of total body mass.
There’s also a possibility to encourage WAT to act more like BAT, which scientists refer to as “brite” adipose (brown + white), or as some other scientists (who were more into color theory than just wordplay) call beige adipose!
Adipose tissue as an endocrine organ
Endocrine organs are organs that send messages via hormones throughout the body to turn on or off different processes. Endocrine organs are critical for maintaining proper functioning throughout the body. Our fat tissue, both white and brown, act as endocrine organs throughout the body–influencing metabolism, energy use, and even sex hormone levels. This means that keeping the human body healthy means keeping the fat tissue healthy as well.
Insulin, estrogen, leptin, and adiponectin are the primary hormones WAT responds to and/or secretes. Insulin is the hormone that drives glucose (blood sugar) into the cells. This is important for our body to be able to utilize the sugar that’s circulating, instead of letting it get too high in the blood, which can cause diabetes. Estrogen is a sex hormone that is central to the female hormone cycle and should be balanced in male hormone health as well. Leptin is involved in hunger and satiety cues and communicates between fat stores and parts of the brain to achieve this. Adiponectin is a hormone involved in balancing fat and glucose uptake in organs like skeletal muscle and the liver. Beyond this, adipose tissue can also regulate the immune system by producing compounds called “adipokines”.
Just like any other endocrine organ–the thyroid, the testes, the adrenal glands, the pancreas–we want to make sure the hormones that are secreted by our adipose tissue are balanced, not too much, and not too little because either end can lead to disease or dysfunction. For example, when the pancreas has been overstimulated and produces too much insulin, our body will stop responding to this incessant signal, called “insulin resistance”. Similarly, when we have too much leptin in circulation from excessive WAT, we can develop “leptin resistance”.
Supporting healthy adipose tissue
All types of adipose tissue are important. There are severe, severe health consequences with too little adipose tissue. Just like there can be serious health consequences with too much of any type of adipose tissue. But this is based on the endocrine functionality of this fat tissue, not just its presence, so it is important for us to support, nourish, and keep in balance, our adipose tissue.
The overwhelming attitude towards adipose tissue in the larger medical world is weight loss at all costs. Instead, our focus should be on supporting a healthy metabolism and endocrine homeostasis for each and every body. This includes proper nutrition, with nutrient-dense and minimally processed foods, and varied & enjoyable movement/exercise which is incorporated into a person’s lifestyle. Another factor influencing the health of adipose tissue is the presence of obesogens in one's life.
Obesogens are a subset of endocrine-disrupting chemicals that we are exposed to in our lives and throughout past generations of our families. This theory upsets the leading assumption that weight gain and weight loss are strictly based on calorie surplus and calorie deficit. Obesogens are chemicals that change our white fat tissue cells so that they not only proliferate, but they store more fat than they normally would. Furthermore, the effects of obesogens last beyond exposure, fat cells affected by obesogens will hold onto this stored fat, even with a change in diet.
It's not only the change in the fat cells storing more fat that is of concern with obesogens. Obesogens may also disrupt the way in which fat cells, which we know are endocrine cells themselves, secrete hormones that affect our metabolism. Fat cells produce an enzyme that converts testosterone into estrogen and they secrete hormones called adiponectin and leptin. With excess estrogen, we may have menstrual-related symptoms. Adiponectin is involved in modulating inflammation and insulin sensitivity, and leptin affects appetite and weight control. If and when these hormones & enzymes are affected, our fat tissue and weight control may be disrupted outside of the control of our diet & nutrition. Obesogens include food additives, alkylphenol surfactants, sunscreen additives, phthalates, bisphenols, and gas additive mixtures. Food additives are compounds that help preserve food or change its qualities. Alkylphenols are organic compounds that belong to a class of synthetic surfactants widely employed in the manufacturing of detergents, adhesives, cosmetics, emulsifiers, and household cleaners. Sunscreens include benzophenone which has been found to be an obesogen.
How does this look in terms of healthcare?
If you’re looking to work with a provider regarding your health in the context of healthy adipose tissue, it should look way different than just being told to lose weight, getting prescribed a diet, and then heading back out into the world. Here’s a general list of what should really be happening…
Revised goal setting. Goals are things that you have direct control over achieving. While having a goal of weight loss is something that some folks have, there are many factors at play that influence body weight. Goal setting should instead be on initiating certain behaviors, such as meal prepping a certain amount of times, or going for a walk each day, not how much weight is lost or gained.
Labs! Adipose tissue is hormonally and metabolically active, so it’s important to see where those levels are at.
A thorough discussion about nutrient-dense foods with strategies of how to incorporate them.
Brainstorming methods of movement and exercise with a focus on sustainability and enjoyment.
Review sources of obesogens in the diet and environment.
Vitamin and mineral support for optimal metabolic function. Certain supplements may be indicated based on lab values or gaps in the diet.
Holistic support for the liver, adrenals, and nervous system. These are organ systems that are critically important to a healthy metabolism!
Analyzing and supporting a balanced microbiome.
Adipose tissue is an amazingly complex organ. Often villainized for its presence and almost completely misunderstood in how to balance its functionality. The more we understand about this critically important organ, the better we can support everyone who has it (which is all of us, by the way!).
Dr. Olivia Froehlich ND
References as PMIDs:
35196429, 29320711, 31903450, 30193906, 30287946, 30234364, 24328657, 25790393, 26579524
References as citations:
Bombak A. (2014). Obesity, health at every size, and public health policy. American journal of public health, 104(2), e60–e67. https://doi.org/10.2105/AJPH.2013.301486
Cheng, L., Wang, J., Dai, H., Duan, Y., An, Y., Shi, L., Lv, Y., Li, H., Wang, C., Ma, Q., Li, Y., Li, P., Du, H., & Zhao, B. (2021). Brown and beige adipose tissue: a novel therapeutic strategy for obesity and type 2 diabetes mellitus. Adipocyte, 10(1), 48–65. https://doi.org/10.1080/21623945.2020.1870060, PMID 33403891
Marlatt, K. L., & Ravussin, E. (2017). Brown Adipose Tissue: an Update on Recent Findings. Current obesity reports, 6(4), 389–396. https://doi.org/10.1007/s13679-017-0283-6, PMID 29101739
Montanari, T., Pošćić, N., & Colitti, M. (2017). Factors involved in white-to-brown adipose tissue conversion and in thermogenesis: a review. Obesity reviews : an official journal of the International Association for the Study of Obesity, 18(5), 495–513. https://doi.org/10.1111/obr.12520, PMID 28187240
Penney, T. L., & Kirk, S. F. (2015). The Health at Every Size paradigm and obesity: missing empirical evidence may help push the reframing obesity debate forward. American journal of public health, 105(5), e38–e42. https://doi.org/10.2105/AJPH.2015.302552
Saito, M., Matsushita, M., Yoneshiro, T., & Okamatsu-Ogura, Y. (2020). Brown Adipose Tissue, Diet-Induced Thermogenesis, and Thermogenic Food Ingredients: From Mice to Men. Frontiers in endocrinology, 11, 222. https://doi.org/10.3389/fendo.2020.00222, PMID 32373072
Scheele, C., & Wolfrum, C. (2020). Brown Adipose Crosstalk in Tissue Plasticity and Human Metabolism. Endocrine reviews, 41(1), 53–65. https://doi.org/10.1210/endrev/bnz007, PMID 31638161
Ulian, M. D., Benatti, F. B., de Campos-Ferraz, P. L., Roble, O. J., Unsain, R. F., de Morais Sato, P., Brito, B. C., Murakawa, K. A., Modesto, B. T., Aburad, L., Bertuzzi, R., Lancha, A. H., Jr, Gualano, B., & Scagliusi, F. B. (2015). The Effects of a "Health at Every Size(®)"-Based Approach in Obese Women: A Pilot-Trial of the "Health and Wellness in Obesity" Study. Frontiers in nutrition, 2, 34. https://doi.org/10.3389/fnut.2015.00034
van Marken Lichtenbelt, W. D., Vanhommerig, J. W., Smulders, N. M., Drossaerts, J. M., Kemerink, G. J., Bouvy, N. D., Schrauwen, P., & Teule, G. J. (2009). Cold-activated brown adipose tissue in healthy men. The New England journal of medicine, 360(15), 1500–1508. https://doi.org/10.1056/NEJMoa0808718, PMID 19357405