The Different Categories of Metabolic Activity

The Different Categories of Metabolic Activity

A living organism needs energy to carry on its chemical reactions to maintain life, such as building, repairing, and keeping homeostasis. Metabolism is the term used in reference to all chemical reactions that happen in a living system, and it can be classified into catabolism and anabolism. Anabolism is the synthesis of compounds, and catabolism is the breakdown of molecules to gain energy. Our body obtains necessary chemicals and energy with the breaking down of nutrients (Mandal, 2016).

In this laboratory report we used body measurements and level of physical activity to determine our total body surface area, how many calories we burn per square meter per hour, our basal metabolic rate, and total daily energy expenditure. These values helped us to find out how many calories intake would be necessary to keep our metabolic reactions, and based on our physical activity level, how many calories per day are necessary to maintain our current weight.

Basal metabolic rate (BMR) is the minimal rate of energy necessary to keep basic metabolic reactions to maintain life, like kidney function, respiration, heart rate etc. The units used to report BMR are energy units per time. There are many factors that influence BMR, some are: sex, age, genetics (race), weight, body surface, fat percentage, body temperature, external environment, glands activity, exercise, and pregnancy. Some variables are correlated, when taking in consideration a person’s genetics and race, their geographic location may influence as well, and the climate and dietary variations may increase or decrease the BMR values among different populations. When taking in consideration weight, heavy people have higher BMRs than smaller people, but the BMR per unit body weight in smaller people is higher. The variable that correlates the most with BMR is the surface area of the body, which is a correlation of height and weight. The greater the body surface, the higher the BMR. Tall and thin individuals have the higher BMRs. Comparing a tall and a short person with the same weight and following the same diet, the taller person would keep their total body mass, while the short one would increase his or her weight (Essentials of Exercise, 2005).

BMR values can be used to help in diagnosis of many diseases. In thyroid disorders, if the BMR is less than 10% of the expected value it can indicate moderate hypothyroidism; in severe cases the values may reach 40-50% below normal. A low BMR also can indicate starvation, under nutrition, Addison’s disease, and lipoid nephrosis. While a BMR above the normal level is observed in fever, diabetes insipidus, leukemia, and polycythemia. BMR is also used to determine the total daily energy expenditure (TDEE) (Schwartz, 1998).

The total daily energy expenditure (TDEE) is the amount of energy (calories) that a person burns per day. Some factors influence TDEE, such as the thermal effect of food, which is the energy necessary for digestion, and the climate since in tropical or

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