Talk:Fundamentals of Human Nutrition/Energy expenditure

Energy Expenditure: Basal Metabolic Rate Basal metabolic rate (BMR) is the minimal rate of energy expenditure per unit time by endothermic animals at rest. (Pike, Brown, 1975). Metabolism is all of the internal and external processes that the body needs to do for proper function. Some of the processes that the body carries out constantly without rest are breathing, blood flow, body temperature control, and the binding of myosin and actin filaments for muscle contraction. When the body generates heats from metabolism, it is called thermo genesis. The amount of heat generated from the body can be measured to estimate energy expenditure. There are a few trends that are associated with basal metabolism. First off, as you increase in age, your basal metabolic rate goes decreases. "This is associated with a decrease in muscle mass, which normally decreases metabolic rate as well."(Saltin, Gollnick, 1983). When comparing two different people of the same age, the person with more lean muscle mass will be have a higher basal metabolic rate. They have more muscles; so that puts a larger demand on the body to circulate blood faster, increase the rate of gas exchange for respiration, and there is more force exerted when muscles contract. Of the body's total energy expenditure, 70% comes from basal metabolic processes from various organ systems in the body. 20% came from physical activity and the last 10% came from thermo genesis. Thermo genesis is defined as the digestion of food. Intake of oxygen and coenzymes are necessary to have all of the body processes work properly for survival. Carbon dioxide needs to be expelled through the Krebs cycle as well. In a general breakdown of the organs that account for energy expenditure, the liver accounts for 27%. This has the highest percentage of energy expenditure because the liver takes part in many different metabolic processes. Next the brain accounts for 19% because it is the control center of the body and is responsible for almost every action in the body. Skeletal muscles account for 18% of energy expenditure and is responsible for the contraction of muscles during movement. The kidneys account for 10% of energy expenditure and are responsible for the excretion of urine. The heart is responsible for 7% of the expenditure of energy because it has the task of pumping blood throughout the whole body. And other organs account for 19% collectively. (Thorstensson, 1976 ) The primary organ responsible for the regulation of metabolism is the hypothalamus. Its functions include control of the autonomic nervous system, production of certain hostile feelings, and regulating the body temperature and food intake as well.

Bibliography Pike, Ruth L; Brown, Myrtle Laurestine (1975). Nutrition: An Integrated Approach (2nd ed.). New York: Wiley. Saltin, Bengt; Gollnick, Philip D. (1983). "Skeletal muscle adaptability: Significance for metabolism and performance".Stephen R. Handbook of Physiology. Baltimore: Williams & Wilkins. Thorstensson (1976). "Muscle strength, fibre types and enzyme activities in man". Acta physiologica Scandinavica.