Metabolism is a term used to describe the reactions that occur within cells to provide energy to the body.
Your body relies on the energy from food and drink to support growth, development, reproduction, and other life-sustaining functions. There are different types of metabolism, and there are a variety of factors that affect how metabolism works.
How Does Metabolism Work?
Metabolism is derived from the Greek word metabolē, which means “change”, and refers to the processes that take place inside the cells to provide energy to the body. Metabolism is also used to describe physical and chemical processes that use energy, such as respiration and digestion.
Metabolic reactions are organized into metabolic pathways, which are chain reactions triggered by enzymes or proteins that act as catalysts for reactions in the body. For example, glycolysis is a metabolic pathway that uses enzymes to break down glucose (sugar) into energy.
These reactions occur constantly, even while you are sleeping, in order to provide your body with a constant source of energy and maintain functions such as heartbeat.
Metabolic reactions are controlled by enzymes and hormones such as insulin, adrenaline, and thyroid hormones. For example, thyroid hormones increase your basal metabolic rate (BMR), which is the energy your body uses to perform its most basic functions at rest. Thyroid hormones also stimulate the metabolism of carbohydrates and the building of proteins.
Your metabolism is affected by factors such as age, diet, gender, activity level, genetics, and health conditions such as hypothyroidism and cancer.
Different Types of Metabolism
Metabolic reactions fall into two categories:
- Catabolic reactions: Catabolic reactions involve the breakdown of larger molecules into smaller molecules. These types of reactions usually release energy. An example of a catabolic reaction is the digestion of food, which provides energy to your body.
- Anabolic reactions: Anabolic reactions produce larger molecules from smaller molecules. Unlike catabolic reactions, anabolic reactions use energy. Building tissues, such as building muscle or bone, is an example of anabolism.
To sustain life and maintain bodily functions such as heartbeat and cell repair, you must provide your body with a steady supply of energy by consuming calories from food and beverages.
Most of the energy or calories your body consumes each day come from your basal metabolic rate (BMR). BMR refers to the energy required for the body’s key functions, such as breathing, blood circulation, and keeping the heart beating while resting. BMR accounts for 50-80% of your daily energy expenditure.
Two other factors that affect total energy expenditure are the thermal effect (TEF) of food and the energy used during physical activity.
TEF, also known as thermogenesis, is the energy your body uses to digest and process food and beverages. TEF accounts for about 10% of total daily energy expenditure.
Certain foods, such as high-protein foods, require more energy to digest than others, so your dietary choices can affect your metabolic rate. Of the three macronutrients (protein, fat, and carbohydrates), protein has the highest TEF.
The amount of energy required for physical exercise, such as exercise, varies depending on your activity level. People who are very active every day and exercise or do physically demanding jobs need more calories to maintain their weight than people with lower activity levels.
Similarly, people who try to gain muscle mass (which is an anabolic state) need more energy than people who try to maintain weight or lose weight.
Factors That Affect Metabolism
Your metabolic rate is affected by a variety of factors, some of which are out of your control. For example, your metabolic rate is partly dependent on your genetics, which means that some people naturally need fewer calories than others to maintain their weight.
Other factors that affect metabolism include:
- Body size: Larger people usually need more energy as compared to smaller people. For example, a six-foot-tall person typically needs more calories to maintain their weight than a five-foot-tall person. However, this is not always the case, as certain factors, such as physical activity levels, can affect energy requirements.
- Gender: Men typically need more calories than women because they are usually larger and have more muscle mass.
- Body composition: People with more muscle mass have a faster metabolic rate than people with low muscle mass and high body fat levels. This is because muscle cells burn energy more efficiently than fat cells.
- Age: As we age, our basal metabolic rate tends to decline. This is associated with muscle tissue loss, reduced activity levels, and other age-related metabolic changes. Studies have shown that basal metabolic rate remains largely stable between the ages of 20 and 60 and then begins to decline after the age of 60.
- Physical activity: People who are active need more energy than those who are low. Regular physical activity can increase muscle mass and increase calories burned at rest (BMR).
- Diet: Diet is another factor that affects metabolism. Protein digestion requires 10-30% of protein energy, while carbohydrates and fats require 5-10% and 0-3%, respectively. This means that your body burns more calories when it digests protein than it does when it digests carbohydrates or fats.
Stimulant medications, diseases, and infections are other factors that affect metabolic rate.
Health Conditions That May Affect Metabolism
Some health conditions can affect your metabolism, which can lead to weight loss or weight gain, as well as other complications.
Thyroid disease can speed up or slow down metabolism, depending on the type. Hypothyroidism or an underactive thyroid causes your body to burn fewer calories, while hyperthyroidism or hyperthyroidism increases your body’s energy needs. That’s why hypothyroidism is often associated with weight gain, which can lead to weight loss.
Other examples of health conditions that affect metabolism include cancer and Cushing’s syndrome. Cancer increases energy expenditure by influencing energy requirements through disease-related metabolic changes and increased inflammation. The increase in energy expenditure is one of the reasons why cancer patients often lose weight.
People with Cushing’s syndrome (a condition caused by high cortisol levels) have difficulty maintaining a healthy weight due to disruption of normal metabolic processes. For example, impaired glucose metabolism affects the way the body digests glucose (sugar), which can lead to weight gain.
Can You Boost Metabolism?
There are certain factors that affect your metabolism that you can’t control, but there are effective ways to increase your metabolic rate.
Following a nutritious diet and maintaining optimal body composition can help increase your basal metabolic rate or calories burned at rest.
A study of 304 obese or overweight women between the ages of 18 and 50 found that women who strictly followed a vegetable, fruit, nut, egg, red, white, and legumes diet had significantly higher BMR than those who followed this diet. Eat a diet rich in processed foods that are high in sugar and fat.
Following a diet rich in natural foods, especially protein-rich foods, is an effective way to increase and maintain your metabolic rate. Protein has a higher TEF than carbohydrates or fats, which means it requires more energy to digest. A protein-rich diet can also help your body maintain a lean body mass, which is essential for a healthy basal metabolic rate.
Staying physically active and supporting muscle mass through resistance training can also increase basal metabolic rate and prevent the decline in basal metabolic rate associated with aging. A review of studies found that resistance exercise increased BMR by about 96 calories per day.
Another small study of 67 people found that nine months of resistance training increased BMR by an average of 5%.
Getting enough sleep is also essential for maintaining a healthy basal metabolic rate. Some studies have shown that sleep deprivation alters metabolism and lowers basal metabolic rate. A small study of 36 people found that sleep restriction reduced basal metabolic rate (BMR) by 2.6%.
While following a nutritious diet, maintaining good health, and getting enough sleep can promote a healthy metabolism, these habits can also promote overall health and help reduce the risk of common diseases like heart disease.
If you have a health condition that affects your metabolic rate, such as hypothyroidism or cancer, you may need medication as well as lifestyle changes to increase your metabolic rate. Your healthcare provider may also recommend medications to prevent side effects associated with a slowed or increased metabolism, such as weight gain and weight loss.
Conclusion
Metabolism refers to the reactions that occur within the body’s cells to provide the body with energy and use the energy to perform bodily functions such as digestion and breathing.
Factors that affect metabolic rate include age, gender, diet, and physical activity level. Underlying health conditions, such as hypothyroidism, can also affect metabolism.
Although some factors that affect your metabolism, such as age and genetics, are beyond your control, following a nutritious diet, staying physically active, and getting enough sleep are effective and evidence-based ways to maintain a healthy metabolism.
