Monday, 14 October 2013 07:44

Metabolism: What Teens Need To Know

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Metabolism is the body’s engine that runs at various speeds to convert the food you eat into energy. It enables your cells, tissues and organs to perform the digestion, respiration, circulation and other functions that keep you alive. Metabolism is measured in calories. You burn calories constantly, whether sleeping, digesting food, watching TV, or running around with your friends. The more active you are, the more calories you burn. But no matter how active you are, between 60 and 70 percent of your calories are consumed daily while you are at rest (Morano, May 2003).


How Does Metabolism Work


To understand metabolism it is important to understand how energy works. All energy is derived from the sun. Plants and algae capture the sun's energy, and store it as carbohydrates. Humans and animals get their energy from plants, which they store as carbohydrates, proteins, and fats.

When humans consume plant or animal products, they are eating energy in the form of carbohydrates (glucose) fats (fatty acids) or proteins (amino acids). A human’s body breaks down theses energy sources (metabolism) through chemical molecules called enzymes so that the energy can be used to fuel the body's cells. Glucose is the primary energy source and provides nearly all the energy required by the body. Amino acids and fatty acids are secondary energy sources which are used once glucose levels have been depleted (Smith, 1999).

As part of this metabolic process there are two functions that happen simultaneously to generate fuel for body functions. These are known as Catabolism and Anabolism:

  • Catabolism refers to the breakdown of food components (such as carbohydrates, proteins and fats) into their simpler forms, which can then be used to create energy. In this process, cells break down carbohydrates and fats to release energy and fuel all anabolic reactions, such as heating the body, giving the muscles power to contract and the body to move (Smith, 1999).
  • Anabolism is your "constructive metabolism" and is all about building and storing. All anabolic processes support the growth of new cells, the maintenance of body tissues, and the storage of energy for use in the future (Smith, 1999).

Hormones that also assist the Metabolism Process

The pancreas and certain specialized cells in the walls of the stomach and small intestine also secrete hormones into the bloodstream as part of the metabolic process. Hormones are chemicals produced in one kind of tissue that regulate function in another kind of tissue; they travel via the bloodstream. Insulin is a hormone secreted by the pancreas. One of its functions is to help glucose get into cells. Gastrin is a hormone produced by the stomach that enters the bloodstream and regulates the secretion of acid and certain digestive enzymes (Morano, May 2003).

Basal Metabolic Rate


The Basal Metabolic Rate (BMR) represents the energy expenditure of all activities experienced on a day to day basis. Your muscular movements, external and internal, glandular activities, muscle tonus, are all controlled by your BMR. Each of us has unique genes and lifestyles, so two teens of identical weight and activity levels will have different BMRs and total calorie consumption. Morano (May 2003) notes that body temperature is one factor that influences BMR. The higher a person’s body temperature, the faster their metabolism is. A second factor is the genes inherited from your parents.

Can I change or manipulate my BMR? Your BMR can be altered by implementing some health changes. Below I have identified a number of changes you can follow that will help increase your Basal Metabolic Rate.


The first change is exercise. When you work out, you not only use more energy, you produce more. Walking, jogging or swimming-and resistance-training with weights will improve your energy by increasing oxygen flow throughout your body. Schedule your exercise as early in the morning as possible. This will establish an upbeat rhythm for the day, and it will help to make sure you do it without getting distracted by day to day events. After lunch and dinner, go for a short walk or climb a few flights of stairs. Keep moving throughout the day, both to burn calories and relieve tension. When at rest, maintain good posture to avoid stressing muscles or causing pain and tension, and to keep your circulation functioning optimally (Bouchard et al. 1989).


The second health change is the food you eat. Begin the day with breakfast and eat sufficiently throughout the day to keep your metabolism from slowing down. When you don't eat, your body goes into a calorie-conserving starvation mode. Not only will you lose energy, but when you do resume eating, your body will be more apt to turn those new calories into fat to prepare for the next self-induced famine. Also it is important that you eat slowly. Start each meal with a few bites of protein, which can stimulate production of brain chemicals that boost alertness. This can help offset the calming effect of carbohydrates. Also it is important that you eat slowly to give your stomach time to tell your brain that you're full so you don't overeat (Bouchard et al. 1989).


The third health change you can make is to eat small meal on a regular basis’. We should all nibble or graze constantly. That way, we wouldn't overload our digestive systems, which makes us drowsy and turns more of what we eat into fat. Eating small amounts frequently keeps your system working at a moderate pace all day. If you can't eat six similarly sized meals a day, cut back a little on what you eat at lunch and dinner, and add a mid-morning and mid-afternoon snack to keep your energy stable and your digestion active throughout the day (Bouchard et al. 1989).











Bouchard, C. and Tremblay, A. and Nadeau, A. et al. 1989. Genetic effect in resting and exercise metabolic rates. Metabolism 38 (4): 364–70.


Morano, R. Metabolism Tune-Up. Vegetarian Times. Issue: 309: May 2003.


Smith, J.C (1999) Understanding Childhood Obesity: University Press of Mississippi. Jackson.



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