In one of my previous blogs I spoke about the ways of measuring the body transformation progress and I touched the subject of body composition. I think, it's time to talk about it in more detail – we need a good understanding of the major constituents of our body and their function in order to set realistic weight loss and body transformation goals . In this blog, I will provide an overview of our body anatomy and functions. That will set up the scene for future discussions about different storage systems that we have, body water and electrolytes, fat distribution, and, most importantly – what elements of body composition can be changed and which cannot and, finally, we might revisit the measurement techniques.
I will use the inside-out approach, starting with the core the core element of our body constitution – our muscles and bones, or the musculoskeletal system to be more scientific.
Musculoskeletal System
As the name implies it includes the skeleton and all muscles, tendons and ligaments that create a framework for all our organs and systems and allow us to maintain posture and to move. It also protects our brain located in our skull (cranium) as well as the internal organs located in the chest and abdominal cavity.
In addition to protection and locomotion, musculoskeletal system is heavily involved in our metabolism. Our bones store large quantities of calcium and phosphate, which can be released into the bloodstream in case of a lack of these minerals in our diet. Also, muscles store glycogen – our glucose depot – and some consider muscles to be the ultimate storage of amino acids as muscle tissue proteins can be used in case of starvation or lack of major nutrients.
Internal Organs
Our internal organ systems are less dynamic – they don't change much throughout our adult life unless we contract some sort of a serious illness e.g. liver cirrhosis, various tumours, cardiomegaly etc. Our central nervous system controls all our body movements and governs our emotions and thoughts – essentially, it defines who and what we are. It remains the same in size and function with some microscopic changes that can be observed in certain conditions like Alzheimer's disease and are beyond the scope of our body composition review.
The same applies to the cardiovascular, respiratory and renal systems – none of these organs change their composition significantly in a healthy individual and they do not serve as a major storage of nutrients. Together, these systems ensure the consumption and delivery of oxygen and removal of by-products of our metabolism such as carbon dioxide, uric acid and many others – essentially, while they might not be the most metabolically active organs, their role is to make sure that metabolism happens in general.
It must be noted though that our cardiovascular system in conjunction with our kidneys (renal system) regulate the fluid retention or loss and the concentration of electrolytes in plasma, which are extremely important for the function of every single cell in our body. More on that in one of the blogs to follow in this series (we will talk about proper hydration and water retention and loss in the context of body transformation).
The situation is slightly different with the gastrointestinal system, which allows us to process all kinds of food by digesting it into individual nutrients, breaking them down into the simplest building blocks such as glucose and other simple sugars, amino acids, fatty acids etc. and then absorbing them, which in turn makes them available to the rest of our organs. Importantly, the functions of the GI system are not limited to just that – it also helps us to “detoxify” or to get rid of many metabolic products that we don't need anymore. Biotransformation of toxic compounds is primarily the liver's job – the liver in general is of special interest for us as it helps processing all kinds of nutrients, it stores some glycogen, it produces bile that is necessary for proper processing of fats in our intestines, and, finally, it is the major detoxification organ in our body. Thus, liver is one of the major players in body composition changes. It must be noted that it can change in size, weight and structural composition, primarily due to pathological processes such as, for example, hepatitis or fatty liver. In many cases, these pathological processes may be related to nutrition.
Also, as the core gastrointestinal organs represent the sections of the digestive tract, which is effectively a hollow pipe, their composition doesn't change much. At the same time, certain portions of the digestive tract might get distended, their walls may become stiffer and thicker, and, most importantly, their contents might change drastically thus changing the body composition as a whole – making us “gain” weight and changing the way we look. Additional point that simply has to be made here for individuals who use performance enhancing drugs is that taking growth hormone will cause internal organs to grow and accordingly – will change the body composition and esthetics rather badly (and in many cases – irreversibly).
The next system that I would like to talk about is the genitourinary system. Actually, I merged two systems – reproductive and renal – into one as they are united anatomically and, of course, both of them play a huge role in our body composition. Urinary system includes kidneys, bladder and urinary tracts. While these organs do not change much in their size, the kidneys play the key role in multiple metabolic processes – I already mentioned regulating water and electrolyte balance and removal of unwanted metabolites and toxins with urine, but there is much more to that as kidneys produce hormones regulating our blood pressure, bone health and red blood cells production. On top of the kidneys we have adrenal glands, which we will discuss as part of the endocrine system.
Our reproductive system is closely tied to the urinary one and is absolutely critical for our development, maturation and sexual dimorphism as it determines the levels of sex hormones, which are essential for bone and muscle development as well as the distribution of lean body and fat mass, our stamina, physical performance and athleticism, and even our psychological traits. Which brings us to the main system that controls our body composition – the endocrine system.
Endocrine system
The endocrine system comprises of multiple organs – endocrine glands – that produce hormones, which are biologically active substances regulating our metabolism. The key glands and hormones would be thyroid and parathyroid glands that produce their respective hormones, pancreas that produces insulin, glucagon and somatostatin, our gonads (testicles and ovaries) that produce sex hormones (including testosterone, adrenal glands that produce a number of hormones regulating multiple aspects of our stress responses and homeostasis and others. While many of the functions of the endocrine system are self-regulated, there is a central regulatory organ that controls our endocrine functioning – the hypothalamus. The hypothalamus is located in the central nervous system and produces various releasing hormones or factors that regulate the work of the pituitary gland, which in turn regulates the production of other hormones all over our body. This three-step process often is referred to as the “axes” e.g. the HPA axis, which stands for hypothalamic pituitary adrenal axis and is our major system that takes care of our stress responses. It is critical both for our survival and our metabolism and I will definitely cover it in a separate blog.
Also, on a separate note I have to mention our visceral fat here after discussing the internal organs, as it covers them (hence the name), and the HPA axis again, which is intimately related to the accumulation of visceral fat or central obesity as a result of chronic stress (or certain diseases associated with high levels of cortisol, our main stress hormone). I promise to cover this subject yet again in another blog as it is extremely important for all of us in modern society.
Skin
Discussion of our body composition would be incomplete without talking about the skin, which technically is the largest organ in our body. Ironically, not everyone realizes that it is an organ - even health care professionals often don't think of it this way. Skin serves multiple functions in addition to creating a mechanical barrier between our body and the environment – it regulates temperature, fights infections, helps producing vitamin D and, on top of all that, it stores fat. The fat layer under our skin is called subcutaneous fat and it can become very thick, thus substantially affecting our body composition and our esthetics. Of note, there are several types of fat in our body and the fat composition and distribution may vary greatly depending on several factors. This subject is so important that I decided to make a special blog on our body fat distribution – I will cover the types of fat such as subcutaneous and visceral fat, their location, distribution and health risks (and benefits) associated with them. We will also talk about spot fat reduction soon.
This brings us to the conclusion of this blog and sets up the scene for the next few, so if you don't want to miss anything, subscribe to my newsletter to stay tuned. I hope that this overview was helpful and concise enough, but if there is something that was not clear to you or you'd like to ask a question, please feel free to ask here, on this website, or on my YouTube channel. All kinds of interactions are welcome!
Sincerely Yours,
Dr.Sam