Home > Clinical Information > What is Body Composition Basically, body composition is the exact physical make-up of your body. Usually, body composition analysis divides the body into two components: body fat and lean body mass. The InBody divides body composition into 3-components, comprising total body water (intracellular water and extracellular water), dry lean mass (proteins and minerals), and body fat. Body water is such a vital component that its balance is the basic indicator of health and fitness. Lean Body mass is made up of about 73% water. The more body fat, the less body water because most body water is included in lean body mass. As fat content increases, the percentage of lean tissue decreases in the body and total body water then drifts down toward 50%. Functions of body water Because of its unique chemical and physical characteristics, water plays several key roles in your life. Water, being the liquid component of blood, participates in almost all the metabolisms in your body. Water in blood serves as an important vehicle for metabolic products - transporting oxygen and nutrients to cells and removing metabolic wastes. For instance, various substances such as nutrients, hormones and antibodies are carried by water in the plasma to the interstitial fluid water between cells. Likewise, waste products are taken out of the cells through water. Without such an effective transportation system, cells cannot be fed nor survive. Therefore, water as transportation for substances in a body is very essential in life. Body water also serves as an important regulator of body temperature. In a way, cells in your body are similar to an engine in a car. As fuel from an engine burns, lots of heat energy is released and in case of overheating, a cooling device is equipped in every car. Your body needs the same system to evacuate the heat from cells out of the body; otherwise proteins and enzymes catalyzing chemical reactions in your body will become denatured. However, several thousands of cell layers constitute our body, remarkably slowing down the process of taking heat directly out of your body. Therefore, interstitial fluid water between cells and plasma water circulating through the blood vessels act as a cooling device for your body just like those in cars. Heat inside your body is absorbed by plasma first, while circulating through blood vessels, it is delivered to skin, then finally gets out of the body. However, the cooling system of your body works effectively when the amounts of plasma and interstitial fluid are adequate. As engines in cars overheat with radiators running out of water, the cooling system of your body cannot function properly with insufficient body water. Therefore, balanced body water is critical in temperature regulation and efficiency of the circulating system. When you exercise in hot weather, it is impossible to evacuate all the excessive heat out of the body only with the cooling system. In this case, the secretion of sweat compensates the first mechanism for temperature regulation and works as the second mechanism of body water. The more active its metabolism, the more water in a cell. This is one of the very reasons why muscle tissues contain much more water than adipose tissues, and more water is required to perform the chemical reactions associated to vigorous activities of muscle. If weight decreases due to water loss, then muscle or water content of other cells will decrease as well. Water loss will cause both extracellular fluid such as plasma and intracellular fluid in your body to decrease on a cellular basis, the capability of energy production within a cell also decreases. Therefore, body water is essential in performing the proper functions of your body. Dry lean mass is what is left when body water is taken out from lean body mass. Dry lean mass is composed of proteins and minerals in your body. Protein is the main component of muscle and the amount of protein in your body determines your basal metabolic rate (BMR). Therefore, developing muscles is to make your body a more efficient energy-consuming machine. By increasing muscle mass, you get a higher basal metabolic rate(BMR). Moreover, minerals are the main component of bones, which support the structure of your body, and since it is closely associated with the amount of physical activity, more muscle content means more bone mass. Since young women with low muscle content are at increased risk for osteoporosis after menopause, they need to exercise regularly to increase their muscles for prevention. Muscle cells contain mitochondria, which are one of the smallest cellular organelles, known as the powerhouses of your body. When you develop muscles, the number of mitochondria increases and consume more fat, the main energy fuel. Diet without any physical activity will cause the loss of muscle content as the weight decreases. This is harmful to your health and is merely temporary weight loss. Therefore, in conducting a weight loss program, it is very important to observe the ratio between fat and muscle(lean body mass). Weight changes on any dietary program, meaning changes in the amounts of both fat and lean body mass, but physical activity helps to maintain and increase lean body mass. Generally as you grow older, the size and strength of your muscles decrease and the metabolic rate declines. It results in having more excessive fat, even though you uptake the same amount of calories. Therefore, at senescence with regular check-ups for body composition, much effort is required to maintain lean body mass. On the other hand, Fat cells do not have the abilities like muscle tissue. In fact, excess body fat is considered storage fat and can be utilized as a source of fuel that can feed the mitochondria and help keep your body running. A certain amount of storage fat is also important for cushioning and protecting the bones, muscles, organs, and for temperature regulation. However, high levels of body fat can adversely affect temperature regulation, as well as overtax the body’s organs and systems over time. Body fat is an energy storage which stores excessive nutrients after consuming what is required in your body and when needed, it is broken down to be used as the energy source. Although phospholipids, cholesterol and essential fatty acids are important components in constructing the cellular membrane, body fat is also one of the crucial components of your body. Once again, the standard amount of body fat for men is 15 ± 5% of their weight and for women 23 ± 5% of their weight. Imbalance between lean body mass consuming energy and body fat storing energy indicates obesity. First, increase or at least maintain lean body mass and lose fat mass. Second, keep the reduced weight. It has already scientifically proven that the amount of calorie-intake, exercise and the changes of body composition are closely related, and for a successful diet it is very important to understand the very principle of losing weight. The absolute principle of weight loss is to consume more energy than to intake. Changes in nutrients, used as the raw materials for energy consumption when dieting, and the consequent changes of body composition are divided into 4 stages. Your body uses glucose as the main energy source when in motion. Glucose is the final product hydrolyzed from carbohydrates. It circulates through blood, and by insulin it is taken up by tissues and used as energy. Glucose provides energy for each day and the surplus is stored as glycogen in the liver and in your muscles. If you do not consume enough carbohydrates, your body uses the stored glycogen as the main energy source by glycogenolysis. When your body falls into the state of starvation, your muscles extract glucose from blood and then consumes the stored glycogen as the main energy source. Carbohydrates consist of a combination of water and glycogen (1g of glycogen contains 2-4g of water), and when it is consumed, water comes out. This is why the amount of urine increases when you are on a diet. During the first stage of a diet, you can easily experience rapid weight loss and that is usually due to water loss. The common sense of weight loss is to lose body fat and resulting in reduced body fat percentage, but as seen in figure 6, the percent body fat rate increases. Since the amount of body fat lost during the given period cannot follow the weight loss, it results in increased percent body fat against reduced weight. After all of the carbohydrates in your body have been consumed for energy, during the first 2 days - first stage, your body can turn protein and fat into glucose by gluconeogenesis, which is a process that turns substances other than carbohydrates into glucose. In other words, if protein is used as an energy source, muscle tissues in your body will shrink, risking your health. Therefore, physical activity should be carried out with a diet to reduce muscle loss to the minimum. Since proteins contain water like carbohydrates, the exhaust of water increases during the second stage as well. When you abstain from eating, you lose 1kg per day no matter how much water you drink. You can get enough calories by consuming 0.2kg of body fat providing 1800kcal, which is adequate per day. Again, rapid weight loss during this period comes from water loss and once you have a regular meal, weight will go up soon. This is the period when your body really starts to use body fat as an energy source and reduces protein consumption. Carbohydrates and proteins provide 4kcal per 1g. In the case of proteins, it is not an efficient energy source because nitrogen has to be removed before it is used as energy. On the other hand, fat provides 9kcal per 1g making it more efficient by two fold. Therefore, weight decreases slowly compared to the earlier stages of a diet during which carbohydrates and proteins are used as energy sources. Moreover, since body fat contains little water, after degradation, water is hardly exhausted. Unlike other tissues, the brain uses only glucose as its energy source and 2 days of an empty stomach will result in all glucose and stored glycogen running out. During this time, the brain uses ‘ketone body’ which reaches the maximum amount on the tenth day of continued starvation. When body fat is used as an energy source, both weight and percent body fat decrease and that is a true diet. If you only drink water, it takes about 10 days or more to reach this point. If it is a reducing calorie-intake diet, it takes 2-4 weeks. At the fourth stage, you lose 0.1~0.2 kg per day at the most. Your body copes with the long-term starvation reducing the basal metabolic rate and the amount of energy consumption reduces making calories from 0.1~0.2 kg of fat dissolution enough for your body. Therefore, 1~2kg of weight loss per day does not mean fat loss, and it is not considered as a true obesity treatment.