Whole Body Metabolism.

xxjacqueline

Whole body metabolism is regulated primarily by your hormones. In this post I will discuss some general principles related to energy metabolism and energy balance. Food is the only source of energy and raw materials from which our body is made. In this way, that old saying you are what you eat is entirely the truth. Your body relies on the food you consume to carry out all of its functions and perform its repairs. Between meals the body converts energy stores into smaller molecules that cells can use for energy. When you eat the body replenishes these stores by converting nutrients into energy storage molecules. The way the body stores and utilizes energy - energy metabolism - is influenced by your eating patterns as well as growth, stress, and metabolic rate. In all cases, whether the body stores or uses energy is controlled by endocrine signals. Two critical concepts drive the control of energy metabolism.

1. Because food intake is not continuous, the body stores nutrients during periods of intake and then breaks down these stores during the period between your meals.

2. The brain is dependent on glucose as its primary energy source. Because of this fact, blood glucose levels must be maintained at all times in the body, even between meals.

When we eat, digestion breaks down the large food molecules into smaller molecules which are then absorbed into the blood stream. Carbohydrates are transported in the blood as glucose, proteins are transported as amino acids and lipids are transported in lipoprotiens. Blood flow distributes these nutrients to tissues throughout the body, where they are taken up by cells. Inside cells, the molecules undergo three potential fates:

1. They may be broken down into smaller molecules. In the process releasing energy that can be used for driving various cellular processes.

2. They may be used to create other molecules needed by cells and tissues for normal functions such as growth and repair.

3. If they are in excess they may be converted to energy storage molecules. The two primary energy storage molecules are glycogen and triglycerides, or fat.

Some small molecules can be inter converted. The ability to do this, plays an important role in whole body metabolism. The energy requiring processes of cells fall into three categories: mechanical work, which is movement of cells. Chemical work which is the formation of bonds during chemical reactions. Transport work which uses energy to move a molecule from one side of a cell membrane to another. The amount of energy expended per unit time is the body's metabolic rate. The metabolic rate of a person is influenced by a variety of factors, including muscular activity, age, gender, body surface area and temperature. the basal metabolic rate (BMR) is the rate of energy expenditure of a person who is awake, laying down and is physically and mentally relaxed and has fasted for at least 12 hours. The BMR represents the energy requirement of performing tasks such as pumping blood. Most BMR expenditure is due to activity in the central nervous system, and skeletal muscle. Which account for roughly 40% and 20-30% respectively. The BMR varies from tissue to tissue, muscle tissue has a greater BMR than fat tissue. This is why muscle burns more calories than fat.

For 3 to 4 hours after a meal nutrients are absorbed during the absorptive state. Nutrients during this time are plentiful in the blood. Glucose serves as the primary source of energy for cells, while fats, amino acids and excess glucose are taken up by liver, muscle and fat cells and then converted into energy storage molecules. The postabsorptive state is the time between meals when the nutrients are not being absorbed. Energy stores are mobilized to provide cells the energy they require. During this phase glucose is used primarily for the nervous system while other systems in the body use different energy sources, such as fat, to spare glucose for the nervous system. In summary, energy is stored in the absorptive phase and then used in the postabsorptive phase. This rule is important because despite the fact that we do not constantly consume food, the body provides a steady supply of nutrients to cells. The body must constantly expend energy to stay alive.

The energy needs of the body is primarily met by glucose. Absorbed fatty acids and amino acids can be used for fuel, particularly if diet is rich in these nutrients but poor in carbohydrates. Amino acids may be used to create proteins. Proteins are not created as storage molecules, they have important structural and functional roles in cells. Because of this fact, proteins are constantly being made and degraded. For this reason, the mass of the body that is protein is stable and does not change solely on the amount of amino acids consumed. Consuming more amino acids will not create more muscle for the body. The body will use protein as a nutrient source only if conditions are extreme, because it does so at the expense of losing functioning molecules. 20 - 30% of the bodies energy reserves is proteins, and some can be used for energy without being harmful. But a continual use of protein for energy is harmful and can be potentially fatal.

Whereas the body is limited in its ability to store energy in other forms it is unlimited in its ability to store energy as fats. The creation of fat is the final pathway for all nutrients that are absorbed in excess of the bodies needs. Fat stores represent 75 -80% of stored energy and contain enough energy to last for about two months.

I was hope this was informative. All information was taken from the book, Principles of Human Physiology.

sophjakesmom

Very interesting. Thanks for sharing!

xxjacqueline

Very interesting. Thanks for sharing!

You are very welcome.

mrb_9110

Thank you for this very interesting post. I want everyone to see this who thinks consuming an excess of 150 grams of protein a day is going to build more muscle.

xxjacqueline

Thank you for this very interesting post. I want everyone to see this who thinks consuming an excess of 150 grams of protein a day is going to build more muscle.

I know! Most people think that consuming massive amounts of protein without strength training will give you huge muscles and that's not the case. I've learned it is a very common misconception.