Metabolism – Processes, Stages, Benefits and more

Health Insurance Plans starting at Rs.15/day*

Health Insurance Plans starting at Rs.15/day*

Metabolism is a collective term for a set of many reactions that occurs in all organisms. The metabolism helps in the conversion of energy for various reactions that take place in our body.

A solar battery converts light and heat into various energy like electricity so that we can use it likewise our body converts the food we eat into energy. The energy generated is used for various chemical and biological reactions that take place within our bodies.

What is metabolism?

Metabolism is a reaction that happens in each cell of our body, which provides us with energy. Metabolism is a collective reaction and the energy produced is used for vital processes like protein synthesis, respiration and transportation.

The process of metabolism is almost the same for all organisms like animals, humans, fungi, bacteria and plants.

The chemical reactions take place under certain conditions like pH and temperature. The rate at which the energy is produced is called the basal metabolic rate.

Two processes of metabolism

The process of metabolism consists of a series of reaction that takes place within the cells and is interconnected with cellular pathways.

Metabolism is categorised into two distinct metabolic pathways. The pathways either maximise the energy or minimises the use. It is divided into two major processes called anabolism and catabolism.


Anabolism is a series of chemical reaction that synthesises complex molecules that are formed in living cells with the nutrients provided.

The synthesis of molecules includes carbohydrates, lipids, proteins and energy-rich compounds like adenosine triphosphate (ATP).

In the cells that are newly developing anabolism dominates over the catabolism process. Anabolism is a state where large molecules are formed by combining small molecules. Some of the anabolic reactions include the development of muscles, bones and other cells in our body.

Anabolism also requires energy and it is consumed through ATP hydrolysis. ATP hydrolysis is a process where the high-energy phosphoanhydride bonds in the ATP are broken and used during the anabolism process.

For example, the glucose needed by the body is produced from other sources by the kidney and liver.

Anabolism is divided into stages. Precursor formation, energy consumption and complex molecule formation.

The precursor formation stage is a stage where large molecules like amino acids, monosaccharides and nucleotides are produced.

During the energy consumption stage, the energy that is obtained from the ATP is used to activate the precursor that is formed during the previous stage to participate in biochemical reactions.

The complex molecule formation stage is where the complex molecules like proteins, lipids and nucleic acids are formed.


Catabolism is a series of enzyme-catalysed reaction that breaks down complex molecules into simpler molecules to release energy or it is used up during anabolism.

During the catabolism, the energy is released in three phases. The proteins and lipids are broken down and a small amount of energy is released in the form of heat.

In the second phase, the formation of any one of the compounds like acetate, oxaloacetate or α-oxoglutarate takes place by oxidising the small molecules.

In the third phase, the compound formed is oxidised into carbon dioxide by process of cyclic reaction called the Krebs cycle.

How does metabolism work?

The organisms process the food they eat in three different stages. The first stage involves breaking down complex molecules into simple molecules. Complex molecules like oligopeptides and free amino acids facilitate absorption.

Complex sugars like disaccharides or monosaccharides and lipids into glycerol and fatty acids. The process is called digestion and it contributes to only 0.1% of energy production.

Oxidation is the process of losing electrons or hydrogen atoms during a reaction. During the second phase of metabolism, the small molecules undergo incomplete oxidation.

The important three substances are acetyl coenzyme A, alpha–oxoglutarate and oxaloacetate and the end-product will be carbon dioxide and water.

The third phase is the Krebs cycle. Acetyl coenzyme A and oxaloacetate together form the citrate. This reaction releases protons which are transferred to the respiration chain to synthesise ATP.

Stages of metabolism

Glycolysis for glucose

Glycolysis is the process where glucose is broken down and energy is produced. During the glycolysis process NADPH, ATP and water are produced.

The process of glycolysis takes place in the cytoplasm of the cell and does not require oxygen. This process occurs in both aerobic and anaerobic organisms.

Glycolysis is the first step of cellular respiration. Glycolysis involves ten stages and can be split into two phases namely, the energy-requiring phase and energy-releasing phases.

Citric acid cycle

A citric acid cycle is also called as Krebs cycle and tricarboxylic acid cycle. The citric acid cycle is the primary source of energy for cells and an important step of aerobic respiration.

In the process of glucose metabolism citric acid cycle is also a part of it and the glucose is oxidised to form pyruvate which is further oxidised and then enters the TCA as acetyl-CoA.

The cycle depends on the intermediates as they are the origin of the pathway that leads to the production of important compounds like fatty acids, amino acids and porphyrins.

If the intermediates are broken the cycle gets diverted and it no longer functions.

Electron transport chain

The electron transport chain is a series of reactions that creates an electrochemical gradient and leads to the creation of ATP in a complete system called oxidative phosphorylation.

It transfers the electrons from electron donors to the acceptors.

What controls metabolism?

The endocrine system controls metabolism. Many hormones control the direction and the rate of metabolism.

The thyroid gland releases a hormone called thyroxine. Thyroxine plays a major role in controlling a person’s metabolism rate. So, if you have a fast metabolism thank the hormone thyroxine.

The pancreas release a hormone called insulin. Anabolic activity occurs after your meal because the blood glucose level increases after your meal.

So, there will be a signal to the pancreas and it releases the hormone insulin to use the glucose that is consumed and the anabolic process will be initiated.

Conditions affect metabolism

Cushing’s syndrome

Cushing’s syndrome is a metabolic disorder caused by the overproduction of the hormone cortisol. It is also called as hypercortisolism.

Females are more vulnerable to Cushing’s syndrome than males. Some of the causes of Cushing’s syndrome include pituitary gland cancer, ACTH tumour, adrenal gland disease and familial Cushing syndrome.

Cushing’s syndrome can lead to complications like high blood pressure, type 2 diabetes, bone loss and loss of muscle strength.

Symptoms of Cushing’s syndrome include muscle weakness, depression, anxiety, headache, skin darkening, loss of emotional control, irritability and cognitive difficulties.


Hypothyroidism is a condition where the thyroid glands do not produce sufficient thyroid hormones.

Hypothyroidism affects middle and old aged women still it can affect anyone. In the early stages, hypothyroidism is not noticeable but causes complications like obesity, infertility and heart diseases.

Symptoms of hypothyroidism include constipation, dry skin, weight gain, puffy face, hair thinning, depression, impaired memory, irregular menstruation and fatigue.

Factors that affect metabolism

The rate of metabolism will not be the same throughout your life. There will be changes and the metabolic rate may change depending on factors like age, physical activity, genes and the food you consume.

Muscle mass

People with muscle have a quick metabolism. Fat content in your body will slow your metabolism and it is hard to build and maintain muscles.


Your metabolism changes as your age. When you were young you would have a quick metabolism whereas as you age you can see the metabolism slowing down. As you age, you tend to lose muscles, this is the reason for your slow metabolism as you age.


It is a known fact that males a have faster metabolism than females. Males tend to have muscle mass and less fat.


Genes also play a major role in metabolism. The inherited genes determine your metabolic rate.

Physical Activity

Physical activity determines your metabolism. Walking, jogging, playing and any other form that increases your heart rate will help you burn more calories.


The cigarette buds contain nicotine. So, when you smoke nicotine helps to reduce weight but it causes life-threatening consequences like cancer and cardiovascular diseases and also increases your blood pressure.

So people who quit smoking may experience an increase in weight. It is better to gain weight than to get affected by life-threatening diseases.

What does your metabolism do?

The metabolism of your body will never stop and it keeps working to provide energy even at rest. The metabolism will keep producing energy for body functions like digesting food, blood circulation, development of new cells, repairs the damaged cells, maintaining body temperature and also bringing a balance in your hormone levels.

Benefits of metabolism

To have a healthy metabolism you have adhere to a few healthy habits.

Don’t skip meals

When you skip your meals, your body tends to store calories. And it also breaks the muscles for energy. The loss of muscle may slow down your metabolism.

So, always keep in mind to eat your food properly on time.

Fuel your metabolism

The body tends to burn calories when you feed it good and healthy food. Give your body a variety of nutrients like fruits, vegetables and lean meat.

Strength train

When you try to lose weight strength training is important. Strength training helps to build muscle and also reduces fat. It makes more place in your body for muscles than fat cells.

Quit smoking

When you stop the habit of smoking, you tend to gain weight. But you can be safe from the risk of heart disease and cancer.

How does metabolism affect weight?

The pace at which your body burns fat is the metabolism rate. When your body burns fat quicker, then you will have a fast metabolism. When your body burns less fat, you will have a slow metabolism.

Your body naturally regulates your body metabolism rate. So, there is less effect on your weight gain.

When should I talk to a doctor?

Extreme fatigue

Fatigue is not only being tired or feeling sleepy all the time. It is more than that. Fatigue may be caused due to many reasons like hormonal changes and also due to food habits.

So, when you feel tired and sleepy most of the day without any reason, consult your doctor immediately.

Weight gain

Weight fluctuations are common, but when you gain weight without consuming too much of calories, consult your doctor.


Metabolism and weight fluctuations are interrelated but it does not mean your metabolism only determines your weight.

Consume healthy food and you can have a cheat meal or a cheat snack once in two days. This can make you eat less and also lowers your cravings when compared to a cheat day.

Prefer home-cooked food to the outside food. Add fruits, vegetables and proteins to your diet. This fuels your metabolism and also helps maintain your weight.


1. What is the process of metabolism?

The process of metabolism involves chemical reactions that change food into energy. This is done by many cells and involves cellular energy.

2.Is high metabolism good?

There is no harm in having a fast metabolism. You tend to burn calories fast. Having a high metabolic rate may make it hard to gain weight.

3.What is an example of a metabolic process?

The metabolic process involves breaking glucose for energy. The energy is used for many functions like breathing, blood circulation and other physical activity.

4.What 5 factors affect your metabolism?

The factors that affect metabolism are age, sex, genes, physical activity, muscle mass and hormonal factors.

5. What makes metabolism fast?

There is no exact reason for a fast metabolism. The foods you consume and your genes determine your metabolism.

6.How much does your sleep affect your metabolism?

During your sleep, the metabolism drops to around 15%.

7.How does a person boost metabolism?

Consume a balanced diet to boost your metabolism. A balanced meal does not mean you have to cut your carbohydrate content. You just have to consume more protein content foods.

8.What is responsible for regulating the body’s metabolism?

Hormones play a major role in regulating your metabolism. T3 and T4 produced by the thyroid gland play a major role in regulating body metabolism.


The Information including but not limited to text, graphics, images and other material contained on this blog are intended for education and awareness only. No material on this blog is intended to be a substitute for professional medical help including diagnosis or treatment. It is always advisable to consult medical professional before relying on the content. Neither the Author nor Star Health and Allied Insurance Co. Ltd accepts any responsibility for any potential risk to any visitor/reader.

Scroll to Top