Metabolism

What is metabolism?

Metabolism is how your body turns food and drink into energy to keep you alive and functioning. It’s made up of all the chemical processes happening in your body’s cells every second. These processes help you breathe, move, heal and more. Keeping these processes balanced is called homeostasis. It’s what keeps your body running smoothly.

When we think about metabolism, we often focus on how our bodies burn calories from food and drinks. This is known as your metabolic rate and includes:

• The energy your body uses for basic functions, like breathing and keeping your heart beating (basal metabolic rate)
• The energy necessary to digest and process food (thermic effect of food)
• The energy your body uses for physical activities

You might think of metabolism as something you can easily change to manage your weight. But there’s actually a lot more happening behind the scenes. Your metabolism is a complex system that plays a huge role in your overall health, not just how many calories you burn.

What does your metabolism do?

Your metabolism is how your body uses energy (which ultimately comes from the sustenance you consume) for everything your body does. Your body’s metabolism never stops — even when you’re resting and sleeping. It constantly sustains basic body functions, like:

• Breathing
• Circulating blood
• Digesting food
• Growing and repairing cells.
• Managing hormone levels
• Regulating body temperature

A healthy, life-sustaining metabolism requires cells to function at rest and adapt to a changing environment. This includes adaptation to periods of:

• Eating
• Fasting
• Starvation
• Physical activity
• Illness or injury
• Pregnancy and lactation

This means that your metabolism isn’t always functioning at the same “rate.” Your metabolism signals your body to use more or less energy during different times of the day and for various reasons.

Metabolic processes

To break down the process of metabolism a little further, here’s a look at how it works. In general, metabolism consists of two main processes: catabolism and anabolism.

Catabolism is the breakdown of macronutrients (carbohydrates, protein and dietary fats) you consume into their simpler forms. For example, your body breaks down carbohydrates into glucose, which enters your blood as blood glucose (sugar). Your body also stores glucose as glycogen — mainly in your muscles and liver. These macronutrients are the basis of the fuel your body uses for all its cells.

Anabolism is the opposite of catabolism. Your body takes smaller units (like amino acids) and puts them together to create bigger structures (like proteins). Anabolism is essential when you get an injury, and your body has to heal. It’s also essential for bone growth and building muscles.

How does metabolism affect weight?

Many people think metabolic problems are responsible for weight gain or loss. But your metabolism naturally regulates itself to meet your body’s specific needs. It’s rarely the sole cause of weight gain or loss. In many cases, if your body uses more calories than you take in, you’ll lose weight (and vice versa). But several factors affect how many calories your body needs — many of which are hard to predict or know.

What’s the difference between a fast metabolism and a slow metabolism?

Someone with a fast metabolism or fast basal metabolic rate (BMR) burns a lot of calories even while at rest. If you have a slow metabolism or slow BMR, your body needs fewer calories to keep it going. Your metabolic rate alone doesn’t determine your body size, and vice versa.

What are metabolic disorders?

A metabolic disorder is any condition that happens when there’s an issue with how your body uses energy to function. There are many types of metabolic disorders because something can go wrong with any of the countless processes involved in metabolism. As you can imagine, these conditions also have a wide range of symptoms.

Issues with metabolism can result from many situations, including:

• Nutritional deficiencies. For example, A lack of vitamin D can lead to poor calcium absorption, affecting bone health. Iron deficiency can result in anemia.
• A lack or excess of calories. Consuming too few calories over time can slow down your metabolism. Consuming excessive calories can lead to weight gain.
• Enzyme deficiencies or issues. Inherited conditions like phenylketonuria (PKU) happen when your body lacks an enzyme necessary to break down certain proteins.
• Hormonal imbalances. Thyroid problems like hypothyroidism can slow down your metabolism, causing fatigue and weight gain. Hyperthyroidism can speed it up, leading to weight loss.
• The effects of medications, substances and toxins. Long-term use of corticosteroids can lead to weight gain and insulin resistance. Excessive alcohol consumption can disrupt liver metabolism.

There are two main groups of metabolic disorders: those you can develop later in life (acquired) and those you’re born with (genetic).

Acquired metabolic disorders

Some metabolic disorders develop during your life. Many of these types of metabolic disorders are endocrine system conditions and involve hormone imbalances. Acquired metabolic disorders may happen due to damaged or diseased organs or because of autoimmune attacks. But there are other causes, as well.

Some examples of acquired metabolic disorders include:

• Diabetes (the most common acquired metabolic disorder)
• Thyroid diseases, like hyperthyroidism and hypothyroidism
• Underweight and obesity
• Metabolic syndrome
• Insulin resistance
• Cushing syndrome

Inherited metabolic disorders

Inherited metabolic disorders, also known as inborn errors of metabolism, are a group of conditions that affect how your body processes certain nutrients or enzymes. They result from a genetic change (variant) in your DNA. You inherit them from one or both of your biological parents.

There are hundreds of inherited metabolic disorders — many of which are rare. A few examples include:

• Glycogen storage diseases
• Hemochromatosis
• Lysosomal storage disorders
• Maple syrup urine disease
• Mitochondrial diseases
• Tay-Sachs disease
• Wilson disease

How can I have a healthy metabolism?

The health of your metabolism and your metabolic rate are mostly out of your control. But these steps may help benefit your metabolism and overall health:

• Eat balanced meals regularly. Don’t skip meals. Your metabolism works best when it has a steady source of energy. Skipping meals or eating too few calories can slow down your metabolism.
• Focus on nutritious foods. Choose fresh fruits and vegetables, lean proteins, whole grains and healthy fats.
• Stay active. Exercise, especially strength training and resistance exercises, helps build muscle. Muscle burns more calories than fat, even at rest. This can boost your metabolic rate.
• Get enough sleep. Quality sleep is essential for a healthy metabolism. Lack of sleep can disrupt your hormones and slow down your body’s ability to use energy efficiently.
• Stay hydrated. Drinking enough water helps your body’s metabolic processes work properly. Even mild dehydration can slow down your metabolism.
• Avoid extreme diets or long-term fasting. Drastic calorie cuts or prolonged fasting can slow your metabolism and cause your body to store energy.

How do I know if I have a healthy metabolism?

Healthcare providers rely on medical tests to check your metabolism (how well your body is functioning overall). The two most common blood tests providers use are the basic metabolic panel (BMP) and comprehensive metabolic panel (CMP). Each test checks multiple essential substances in your blood. They provide helpful information about your body’s chemical balance and metabolism.

Providers usually recommend one of these tests at least annually for adults. Your provider may recommend them more frequently if you have risk factors like diabetes, high blood pressure or obesity. Several other types of blood tests and urine (pee) tests can assess many metabolic issues, as well.

If you’re concerned about your metabolism or notice unusual symptoms, like unexplained weight changes or fatigue, talk to your healthcare provider. They can recommend the right tests to better understand your body’s health and help you take proactive steps to improve it.