METABOLISM

Metabolism is the body’s process of creating and using energy to support functions such as breathing and digesting. Because we cannot create our own energy from the Sun like plants can, we need to consume food to get energy. If our bodies were not constantly metabolizing food, then we could no longer live. Metabolism involves many complex chemical reactions in the body that enable a person to get a certain amount of energy—measured in calories—from eating an apple or even more energy from a slice of pizza.

Unused energy is stored in the body as fat. Energy reserves are a great survival mechanism, particularly in the days when famine was a threat. In the United States, scarcity of food is no longer a serious threat to survival so people do not have an opportunity to burn these energy reserves or fat. Americans also lead much more sedentary lives than people once did, often going from car to office cubicle with little physical exertion. In contrast, a pioneer who was chopping wood for hours a day would have much less chance of being overweight given the pioneer’s high caloric needs. The abundance of food and reduced physical exertion in the average American’s life has contributed significantly to the problem of obesity in the United States.

The metabolism rates of people vary, which plays a significant role in who will struggle with weight even if eating well and exercising. As a person ages, his or her metabolism will slow down, which contributes to weight gain in older years. Occasionally you will hear people mention that their weight gain is from a thyroid problem. A problem with this gland can definitely affect a person’s weight. The thyroid gland produces a hormone called thyroxine, which affects the speed of metabolism. If the thyroid is damaged, it may become less active with the result of lowered metabolism. This condition is referred to as hypothyroidism. Individuals with hypothy-roidism feel tired, feel constipated, and may have a slower heart rate. The opposite scenario is hyperthyroidism, when the thyroid is too active. The result of an overactive thyroid is weight loss, increased blood pressure, elevated heart rate, protruding eyes, and sometimes even a swelling of the neck referred to as a goiter.

Another factor affecting someone’s metabolism is how much muscle he or she has and how much he or she exercises. Generally, a higher percentage of muscle versus fat on the body increases the metabolism. Exercise can increase metabolism because the body is burning more calories while running, jumping, or walking than while sitting still. The rate at which a person burns calories by sitting still is referred to as basal metabolism. Basal metabolism varies among people and is greatly influenced by genetics. Basal metabolism can be increased by becoming more physically fit. Another way to increase basal metabolism is by taking weight-loss drugs that stimulate the body’s metabolic rate.

Source: "Drugs The Straight Facts: Weight-Loss Drugs," Chelsea House, 2009