In one way or another, all of the processes that sustain life involve energy. Some of these processes use energy and others release it. But how exactly does energy relate to metabolism?
When you hear the word metabolism, what comes to mind? If you’re like most people, you immediately think about the rate at which your body burns energy or calories as it relates to weight management.
However, that’s what’s known as metabolic rate. Metabolic rate is just one part of metabolism, whereas metabolism as a whole includes much more beyond this.
Aside from impacting your weight, the way the human body uses and transforms energy can profoundly affect every aspect of how you feel and function, including your risk for many chronic illnesses.
In this article, we’ll explore the all-encompassing topic of metabolism, shed some light on common misunderstandings, and offer tips to support essential metabolic functions in your body.
What is Energy Metabolism?
Energy metabolism, often referred to as cellular metabolism, is a term used to describe how cellular energy is produced and used by your body, as well as the amount of energy produced. One of the stars of the show is a cellular organelle known as the mitochondria. Though not all metabolic reactions occur in the mitochondria, many of them do.
As we mentioned earlier, many people mistake metabolism for metabolic rate, which refers to the rate of energy expenditure in a given period of time. It’s important to remember that metabolic rate and metabolism are slightly different terms—metabolic rate is just one factor encompassed by metabolism.
Think about it like this: your couch is just one item in your house, but your house isn’t only made up of your couch—it has a lot of other stuff too. In this example, metabolic rate is the couch and metabolism is the house.
Some people may use the term energy metabolism to describe how your body derives energy from foods. This process of taking larger macromolecules like proteins, carbs, and fats, and breaking them down into smaller molecules to produce energy is one arm of metabolism known as catabolism.
Metabolism as a whole encompasses two arms or categories of chemical reactions: catabolism and anabolism.
How Does Metabolism Work?
Chemical reactions that take place inside living organisms are called biochemical reactions. The sum of all the biochemical reactions in an organism is referred to as metabolism.
You might picture a vast interconnected system of biochemical pathways like a road map communicating the language that keeps life moving along. These roads require enzymes to help make life happen. Enzymes, in turn, often require nutrient helpers, or cofactors.
With this, you can begin to see how nutrition plays a huge role in all areas of metabolism. Without nutrients in their proper amounts and ratios, many enzymatic reactions won’t operate at their best and neither will your many metabolic pathways. And that fact may negatively impact many key metabolic functions you’ll learn about below.
As you now know, metabolism isn’t just the rate at which you burn energy. Rather, it encompasses all biochemical processes occurring in your body to keep you alive.
The Two Arms of Metabolism: Catabolism and Anabolism
To simplify things a bit, it helps to split metabolism into two broad categories: catabolism and anabolism.
Catabolism
Catabolic reactions break down larger molecules into smaller units and release energy in the process. Catabolism can include the breakdown of proteins, fats, and other carbohydrates like fructose and glucose as well as alcohol to produce energy. These are considered primary sources of energy for your body.
An example of a catabolic reaction in your body involves the breakdown of glucose or during cellular respiration, which releases energy that cells need to carry out life processes. Glucose metabolism involves both aerobic and anaerobic processes.
In the case of your body, metabolic energy is transported by high-energy phosphate groups, and most famously in ATP, or adenosine triphosphate, which is often called the “energy currency of the cell”.
Catabolic reactions generate heat as well as help make a lot of ATP. Your body then uses that ATP to power other types of important cellular processes. This brings us to the second and equally important arm of metabolism, anabolism.
Anabolism
Beyond using ATP to power raw physical exertion and muscle action, your body also needs ATP molecules for many anabolic processes, also known as biosynthesis reactions.
Anabolic reactions absorb energy and then build bigger molecules from smaller building blocks produced in catabolism. An example of an anabolic reaction is the linking of smaller amino acids to form a larger protein or combining fatty acids to form triglycerides.
When your body makes hormones, neurotransmitters, new DNA or even new cells, these are all anabolic processes. Storing energy in adipose tissue or glycogen is also an anabolic process.
A Closer Look At Catabolism
As you eat your next meal, chances are it might have a combination of protein, fat, and carbs. So how do these raw materials end up transforming into the energy that powers your body? This happens in three different stages.
Stage One: Digestion
The first stage is all about taking those large macromolecules like protein, fats, and carbs and breaking them down into simpler versions. Proteins are broken down into free amino acids, complex carbohydrates may be broken down into disaccharides or monosaccharides, and lipids are broken down into free fatty acids.
Your digestive system plays an important role here, as each step along the digestive process requires a unique environment. Dozens of different enzymes and other specialized signaling molecules along the way are required to get the job done. Some nutrient absorption may occur in the stomach, but most of it occurs in the upper part of the small intestine.
Stage Two: Nutrient Transport and Absorption
Nutrients released by the processes of digestion must now get into the cells where they can be further broken down for energy. Nutrients don’t simply flow freely into cells and instead require specialized transport systems that shuttle them into the cell.
Glucose, for example, is transported into the cells of many different tissues by the GLUT family of transporters. Amino acids from protein have their own separate system of transporters. Fats or lipids have an entirely different set of processes they must undergo to get inside the cell.
Many things can dictate how well your body absorbs nutrients, including your gut health.
Stage Three: Energy Production and Release
Once inside the cell, the goal is to further break down these molecules through a process of oxidation. This helps to produce two main products of interest: acetyl coenzyme A (acetyl CoA) and oxaloacetate.
These then take a little journey through something called the tricarboxylic acid or TCA Cycle (also known as the Krebs Cycle or citric acid cycle). The final result is ATP.
Below are a few examples of the catabolic pathways breaking down carbs, proteins, and fats. Each process requires specialized enzymes and vitamin/mineral cofactors or helpers:
- Glycolysis: A process where glucose is broken down to produce energy.
- Glycogenolysis: A process where stored glycogen is broken down into individual glucose units. Glucose can then go on to be further degraded through glycolysis.
- Beta Oxidation: A process where fatty acids are broken down for energy.
- Lipolysis: A process where stored fats are broken down into glycerol and fatty acids, which can be further degraded by pathways like beta oxidation (for fatty acids) and gluconeogenesis (for glycerol).
- Gluconeogenesis: A process where certain amino acids and other compounds (glycerol, lactate, pyruvate, and propionate) may be converted to glucose. From there, glucose can undergo further breakdown in glycolysis.
A Closer Look At Anabolism
As catabolism has taken those more complex macronutrients from your meal and broken them down for energy, your body can now use that energy to accomplish quite a lot.
Energy Storage
ATP is an energy reservoir, and in times of adequate nutrition intake, ATP can help supply the energy needed for maintenance as well as repairing and building new tissues like muscle.
When it comes to storing energy, you’re probably familiar with some basic ways your body stores energy in larger macromolecules like fat or glycogen. Glycogen and fat stores may help the body regulate glucose homeostasis and play a role in metabolic flexibility.
Your body does not store extra protein. However, if you are consuming too few nutrients to meet your body’s needs, your body may break down muscle and visceral protein to help keep you alive. This unfortunately may result in loss of muscle mass and even a lower metabolic rate, among other negative health effects.
Building and Repair
Speaking of building muscle, muscle protein synthesis is one of the most important anabolic processes happening in your body. Lean muscle mass not only helps support a healthy metabolic rate and maintain a healthy weight, but it helps your body more effectively process glucose and keep blood sugar balanced.
Every day, many unseen metabolic reactions are taking place that enable your body to repair itself. This includes repair of DNA, cell membranes, tissues like skin and muscle, and much more.
Regulation of Metabolism
It might sound a little funny to say, but the regulation of your metabolism is itself a metabolic process. And like all other metabolic processes, it requires a give and take of energy and a careful balance of nutrients.
Many processes take part in the regulation of metabolism, including:
- Genes, including how genes are transcribed or modified after translation (which can be influenced by diet and environmental factors)
- Hormones
- Nutrition factors, including food type, timing, and amount
- Cellular stress
- Age
Tips For Supporting Your Metabolism
Your metabolism has a lot going on and there’s no magic pill or single solution for optimizing it. It takes a village to support your metabolism. But thankfully, that village is within reach when you consider these healthy lifestyle habits.
Meet Your Nutrient Needs
You should now understand the unique importance of nutrition in supporting your metabolism as a whole. The best diet to support your metabolism is one that is personalized to your individual needs.
After all, your metabolic pathways are a lot like your fingerprint, in that how they operate is somewhat unique. That being said, here are some tips to help point you in the right direction:
- Look to a diverse range of whole foods to build the foundation of your nutrient intake
- Reduce added sugar and ultra-processed foods
- Avoid unnecessary over-reliance on supplements
- Ensure you are eating enough protein, fiber, and essential fatty acids
- Assess your tolerance to carbs and customize your intake to match your needs
- Stay well-hydrated with good quality water
Find the Balance with Stress
Finding a balance with stress is all about finding out which type of dietary approach, exercise routine, and amount of rest your unique body needs to feel its best. It also means taking steps to reduce psychosocial stressors that negatively impact your wellbeing.
This will always be a work in progress, so embrace the journey! Being compassionate with yourself as you navigate the ups and downs is an important way to help reduce your stress too.
Monitor Your Body’s Feedback
Self-monitoring in its many forms can be a powerful tool for recognizing what does and doesn’t work well for your body. This can be in the form of following your doctor’s recommended updates on lab work, tracking your symptoms over time as you try different approaches, and even trying a period of monitoring your glucose levels with a CGM for additional metabolic insight.