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Home / Wellness

Understanding your metabolism


The human body is made up of trillions of cells with their own structure and function.

These cells, continuously busy carrying out thousands of internal chemical reactions, are linked together to keep the body alive, healthy and functioning properly through functions like breathing, blood circulation, growth and repair of cells and respiration.

All these processes are collectively called metabolism.

These internal processes require energy measured in calories or kilojoules primarily coming from the food we eat. How much energy your body burns or spends at any given moment is affected by your metabolism.

Three components of metabolism

Your metabolic rate, or the rate at which your body burns energy has three components. Even when the body is resting, it needs energy to keep you alive and for all systems to function properly.

The lowest amount of energy that your body needs to carry out these processes is known as basal metabolic rate (BMR).

BMR is simply the number of calories the body needs to keep the body functioning while at rest. It accounts for the largest amount of energy or calories used every day, about 50 to 80 per cent of your body’s daily energy/calorie needs.

Thermogenesis or thermic effect of food is the energy the body uses to digest, absorb, transport and store the food you consume. This accounts for approximately five to ten percent of all calories the body uses daily.

Energy used during physical activity and exercise accounts for the rest of the body energy requirements This includes both planned exercises like running and swimming, and other activities done all day that are not deliberate like yawning, blinking and fidgeting.

This energy varies the most depending on how much energy you use per day. A moderately active person engaging in daily physical exercise of moderate intensity can use up to twenty percent of all the energy they burn per day.

What affects your metabolism?

Metabolic rate is affected by very few factors, factors that we mainly have little or no control over. How fast or how slow your metabolism work is mainly determined by your genes.

You either have a slow, average or fast metabolism. These differences in metabolic speed manifest easily when people are trying to lose weight.

A slow metabolism burns fewer calories which means more get stored as fats which makes it very difficult for such people to lose weight just by cutting calories.

On the other hand, people with high metabolism burn more calories even at rest and can eat more and not gain any weight.

Muscles mass is another determinant of a person’s metabolic rate. Muscles are metabolically more active meaning they burn more calories than fat.

The more muscles you have, the more calories you burn even when you are resting compared to a person with more body fats and less muscles.

Your gender determines how fast or how slow you burn your calories. Naturally, men have more muscles and less fat compared to women hence use more calories.

Age is a key determinant of a person’s metabolic rate. As a person ages, their metabolism slows down even for those who start out with a fast metabolism.

In addition, as a person ages there is gradual loss of muscle mass coupled with a steady gain of body fat which slows down energy expenditure. This decline is faster especially in people who are not physically active.

 In order to lose weight, it is important to understand your metabolism so that you can easily create a deficit by eating fewer calories or by increasing the number of calories you burn through physical activity.

Although you have very little control over your basal metabolic rate and food thermogenesis, you can definitely control how much calories you burn through increasing your level of physical activity.

The more active you are; the more calories you burn. Combine both aerobics and strength training to burn calories and build more muscles and consequently improve your metabolic rate.


- The writer is a registered nutritionist

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