What Is Metabolism And What Are The Factors That Affect It?

What Is Metabolism And What Are The Factors That Affect It?

Metabolism basically refers to all the chemical processes that go on continuously inside our body that allow life and normal functioning. The process of maintaining normal functioning in the body is called homeostasis. Furthermore, these processes include those that break down nutrients from our food and those that build and repair our body. 

Generally, building and repairing the body requires energy that ultimately comes from our food. The amount of energy that our body burns at any given time is quite affected by our metabolism and is measured in kilocalories(kCal).

In case we eat and drink more kilocalories than we need for our metabolism and exercise, we tend to store it mostly as fat. 

Processes Of Metabolism

Our metabolism basically has two parts, which are carefully regulated by the body to make sure they remain in balance. They are:

  • Catabolism- This process relates to the breakdown of food components such as carbohydrates, proteins and fats into their simpler forms, which can further be used to create energy and provide the basic building blocks needed for growth and repairs.
  • Anabolism- this process relates to the part of the metabolism in which our body is built or repaired. It requires energy that ultimately comes from our food. When we actually eat more than we need for our daily anabolism, the excess nutrients are typically stored in our body as fat.

Rate Of Metabolism

Our body’s total energy expenditure or the metabolic rate can be divided into three components which are:

  • Basal Metabolic Rate (BMR) – It is nothing but the amount of energy in kilocalories(kcal) burned at rest. In other words, it includes the energy the body uses to keep all its systems functioning correctly. According to various studies, it accounts for the largest amount of energy expended daily (50-80 per cent of our daily energy use). 
  • Energy used during entire physical activity – It is found that in a moderately active person that is about 30-45 minutes of moderate-intensity physical activity per day, this component contributes 20 per cent of daily energy use.
  • The thermal energy of food – it is basically the quantum of energy we use to eat, digest and metabolise food. Also, this contributes to about 5-10 per cent of our energy use.

Basal Metabolic Rate (BMR)

The BMR simply refers to the amount of energy your body needs to maintain homeostasis. Our basal metabolic rate is largely determined by our total lean mass, especially muscle mass because lean mass requires a lot of energy to maintain. Anything that generally reduces lean mass will drastically reduce your basal metabolic rate.

It is very important to preserve or increase your lean muscle mass through exercise while trying to lose weight because our basal metabolic rate accounts for so much of our total energy consumption. While exercise increases your daily energy expenditure, maintaining lean muscle mass also helps to reduce the chances of injuries when you are training.

An average male has a basal metabolic rate of around 1670 kCal per day while an average female has a basal metabolic rate of around 1410 kCal per day. Energy expenditure of our body is continuous while the rate varies throughout the day. This rate of energy expenditure of our body is usually lowest in the early morning.

Energy Used During Entire Physical Activity

During heavy physical exertion or activity, the muscles generally burn through as much as 717 kCal per hour. Typically, the energy used during exercise is the only form of energy expenditure that we have any control over.

In general, the energy expenditure of the muscles makes up only 20 per cent or so of the total energy expenditure at rest. But during strenuous or tiring exercise, it may increase up to 50 fold or more. Estimating the energy expenditure during exercise is difficult as the true value for each person will vary based on factors such as their weight, age, health and the intensity with which each activity is performed or undertaken.

Influences On Basal Metabolic Rate

Our basal metabolic rate is influenced by multiple factors working in combination that includes:

  • Body Size – Larger body size or larger adult bodies have more metabolic tissue and thus a larger Basal Metabolic Rate.
  • Quantity of Body Fat – Fat cells are basically sluggish and burn quite fewer kilocalories than most other tissues and organs of the body.
  • Quantity of Lean Muscle Tissue – Lean muscles are associated with muscle types that burn kilocalories rapidly.
  • Crash diet, Starving or Fasting – Eating too fewer kilocalories encourages the body to slow down the metabolism to conserve energy. Basal metabolic rate can simply drop by up to 15 per cent also loss of lean muscle tissue further reduces basal metabolic rate.
  • Age Factor – Metabolism generally slows down with age due to loss of muscle tissue, but also due to hormonal and neurological changes.
  • Growth Factor – It is found that infants and children have higher energy demands per unit of body weight due to the energy requirement during the growth stage and also because the extra energy needed to maintain their body temperature.
  • Gender Factor – Basically, men have faster metabolisms than women because they tend to have a larger body as compared to their other counterparts.
  • The predisposition of Genes – Our metabolic rate is partly decided by our genes.
  • Hormonal and Nervous Control – Hormonal imbalances basically influence how quick or slow the body burns kilocalories thus basal metabolic rate is controlled by the nervous and hormonal systems.
  • Environmental Temperature – In case the surrounding temperature is very low or very high, the body has to work harder to maintain its normal body temperature which increases the basal metabolic rate.
  • Infection or Illness – when there is an infection or illness as an immune response, the body has to work harder to build new tissues which increase basal metabolic rate.
  • Amount of physical exercise – hard-working muscles needs plenty of energy to burn. Regular exercise increases muscle mass and eventually teaches the body to burn calories at a faster rate even when at rest.
  • Drugs – Few of the drugs like caffeine or nicotine also tend to increase the basal metabolic rate.
  • Dietary Deficiencies – Generally, diets that are low in iodine reduces thyroid function and slows down the metabolism.

Metabolism And Hormonal Disorders

Essentially hormones help regulate metabolism. Some of the more common hormonal disorders are related to the thyroid. The thyroid is the gland which is responsible and secretes hormones to regulate many metabolic processes. It also includes energy expenditure that is the rate at which kilocalories are burned.

Thyroid disorders generally include:

  • Hypothyroidism or underactive thyroid – with the underactive thyroid the metabolism slows down because the thyroid gland does not release enough hormones. The most common cause for it the autoimmune condition called Hashimoto’s disease. Few of the symptoms of hypothyroidism include unusual weight gain, lethargy, depression and constipation.
  • Hyperthyroidism or overactive thyroid – The thyroid gland releases larger quantities of hormones than necessary and speeds the metabolism. Few of the reasons behind this condition is Graves’ disease. Few of the symptoms of hyperthyroidism include increased appetite, weight loss, nervousness and diarrhoea.

Age-Related Weight Gain And Metabolism

Muscle tissue has basically a large appetite for kilojoules, the more muscle mass we have, the more calories we will burn.

People usually put on fat as they age because our body slowly loses muscle. It is still not clear whether muscle loss is a result of the ageing process or because of the reason that people are less active as they age. Nevertheless, it probably has more to do with becoming less active as studies have shown that strength and resistance training can reduce or prevent this muscle loss.

So, before you embark on any new fitness program and you are over 40 years of age with a pre-existing medical condition or have not exercised in a while, you must see your primary health care. 

Genetic Disorders And Metabolism

Our genes are nothing but the blueprints for the proteins in our body. And these proteins in our body are responsible for the digestion and metabolism of our food. A faulty gene basically means our body has produced a protein that is ineffective in dealing with our food thus, resulting in a metabolic disorder. In most instances, these genetic metabolic disorders can be managed under medical supervision with close attention to diet. 

Mostly, the symptoms of genetic metabolic disorders can be quite similar to those of other disorders and diseases making it very difficult to pinpoint the exact cause. You must immediately see a doctor if you suspect you have a metabolic disorder.   

Few Of The Genetic Disorders Of Metabolism Include:

  • Fructose Intolerance – it is a condition which states the inability of our body to break down fructose, which is a type of sugar found in fruit, fruit juices, sugar and certain vegetables for instance cane sugar. 
  • Galactosaemia – it is a condition which states the inability to convert the carbohydrate galactose into glucose. Galactose does not exist by itself in nature, it is produced when lactose is broken down by the digestive system into glucose and galactose. Few sources of lactose include milk and milk products such as yoghurt and cheese.
  • Phenylketonuria (PKU) – it is a condition which depicts the inability to convert the amino acid phenylalanine into tyrosine. It is found that high levels of phenylalanine in the blood can cause brain damage. This the reason why high-protein foods and foods containing the artificial sweetener as far as possible must be avoided. 

Significance Of Basal Metabolic Rate:

  • The determination of basal metabolic rate forms the principal guide for diagnosis and treatment of thyroid disorders.
  • In case the basal metabolic rate is less than 10% of the normal, it indicates moderate hypothyroidism. Also, in extreme hypothyroidism, the basal metabolic rate may be decreased to 40 to 50 per cent below the normal stats.
  • The basal metabolic rate helps us to know the total amount of food or calories required to maintain body weight.
  • The basal metabolic rate is found to be very low in starvation, undernutrition, hypothalamic disorders, lipoid nephrosis and Addison’s disease.
  • In case of fever, diabetes insipidus, leukaemia and polycythemia, the basal metabolic rate is above normal.

Thermal Or Thermic Effect Of Food

Our basal metabolic rate specifically rises after we use energy to eat, digest and metabolise the food we have just eaten. The rise in a rate soon takes after we start eating and peaks two to three hours later.

This rise in the basal metabolic rate can range anywhere between two per cent and 30 per cent, depending on the size of the meal and the types of food eaten.

Different foods have a different impact on the rise of basal metabolic rate for instance:

  • In the case of fats, BMR rises at the rate of 0-5 per cent
  • For carbohydrates, BMR rises at the rate of 5-10 per cent
  • In the case of proteins, the BMR rises at the rate of 20-30 per cent
  • Hot and spicy foods for example foods that contain chillies, horseradish and mustard can have a significant thermic effect. 

Metabolism And Our Health

Metabolism is severely impacted by our health issues. Wherein Hyperthyroidism can increase your metabolism and cause sudden weight loss, sweating or an altered heartbeat. On the other hand, Hypothyroidism can disrupt metabolism and lead to obesity, joint pain and even infertility. 

Metabolic syndrome is associated with the collection of conditions that include:

  • Obesity
  • High blood pressure
  • Increases blood sugar
  • Increased level of blood triglyceride, a kind of fat and also altered blood cholesterol levels that tend to increase the risk of heart disease
  • Diabetes
  • Stroke

This clearly shows metabolism affect our health predominantly. It is also evident that people have different metabolic rates, and that has an influence on people’s weight.

The energy you expend each day is mostly used to keep all the systems in your body functioning properly. This is primarily out of our control. However, we can make the metabolism work for us when we exercise.

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