How the Body Uses Energy: Your Guide to the Body’s Fuel Sources

It’s no secret that the body needs energy – we’ve all had those days where our limbs are heavy, our eyes just can’t seem to stay open, and all we want to do is spend the day on the couch! But do you know how the body uses energy? Have you ever asked yourself “where does our body’s energy come from”? Or what the best foods to boost energy are? Well, look no further! We’ve got a whole bunch of energy information coming your way!

The Body’s Fuel Sources

When we talk about energy, it’s important to first understand where the body’s energy comes from. You may already know the correct answer – food! But not all foods are equal when it comes to the energy being provided, so let’s break it down! Dietary sources of energy fit into 3 main categories: carbohydrates (carbs), protein, and fat. These are known as our macronutrients, which means that we use these nutrients in the largest quantities.

Carbohydrates and protein both provide roughly the same amount of energy per weight - 4 calories per gram. Fat on the other hand, provides about 9 calories per gram. Now, you may be thinking – if someone is trying to fight fatigue, then they should just eat more fat, because this would provide the highest energy density. You’re not wrong in thinking this way, but you must also consider how the body will use the energy given to us by these macronutrients.

How the Body Uses Energy

While fat does provide the most energy per serving, it doesn’t necessarily mean that it will be used for immediate energy. In fact, carbohydrates are primarily used for quick or immediate energy if we’re lacking – for example, just as you’re starting a jog. This is because carbohydrates are easily broken down into sugars, of which glucose is our primary source of fuel for the body. Fats on the other hand, have to be broken down into fatty acids which are then used for fuel during longer duration, low to moderate intensity activity. Now, you’re probably wondering, can protein be used for energy? While protein can be used in some part for energy, it’s primary role is to maintain muscle, help with growth and repair, and to help make hormones, enzymes, and basically coordinate bodily functions as a whole.

How the Body Uses Energy During Exercise

Of course, our energy is used differently during exercise – after all, we need that extra boost to get through a tough workout or huge hike through the woods! Like we already mentioned, glucose is our most readily available form of fuel, both at rest and during early stages of exercise. But, our available glucose supply only lasts a short while after exercise has started, so our body begins to convert stored glucose (known as glycogen) back into glucose to maintain our blood sugar levels. Depending on the type of exercise you’re doing as well as the duration, the carbohydrate content of your diet can impact how much stored glycogen your body has, which can significantly affect both your training and your recovery process. 

During exercise, fat is also broken down to provide us with energy - thank goodness because our glucose only lasts us several minutes after exercise has started. When fat is being used to supply energy, our stored fat is converted into fatty acids, which are then transported to our muscles for fuel. 

When it comes to protein, our bodies don’t often use it as fuel. Instead, protein is used for the many other jobs listed above although it may contribute up to about 5% of fuel for the body. In certain situations however, for example when we don’t consume enough calories or very little carbohydrates, our muscle proteins can be broken down to be used as fuel. Our bodies are pretty amazing aren’t they?!

4 Fun Facts About Energy

About 50-80% of Your Daily Energy is Needed For Rest

While exercise is often thought of as the main consumer of bodily energy, it’s actually rest that requires about 50-80% of our daily energy! Why? Simply put, we have to maintain our vital functions. This includes things like maintaining our organ functions and breathing - I mean, we can’t expect our heart (a muscle) to literally work 24/7 without a solid source of energy! The actual amount of energy used to maintain our vital functions varies from person to person, and is called the basal metabolic rate (BMR). Factors like age, muscle mass, genetics, height, and weight all contribute to how much energy the body consumes at rest.

Eating Also Uses Valuable Energy 

Did you know that eating also uses energy? It’s kind of a funny process, but as we take in food our body has to use up energy in order to break down foods. This way, we can extract valuable nutrients from them. Then, when we eventually need to eliminate any leftovers from the body, this also takes energy which is used to churn, contract, and eventually allow waste to exit the body. All in all, the process of eating, digesting, and metabolizing can use about 10% of our bodily fuel!


The Only Constant is Change, So Make Sure Your Energy Comes From Nourishing Foods

The body is constantly being built and broken down through processes called anabolism and catabolism. What this means is that the nutrients and energy we take in from food are incorporated into our bodies to help us live. For example, amino acids from proteins are used to create hormones, enzymes, and to help build and repair tissues. At the same time, stored glycogen, fats, and proteins are being broken down into simpler molecules for energy, to detoxify chemicals, and to help regulate metabolism. The important takeaway here is that because our bodies are currently in a state of change, our nutrition is absolutely essential to ensure that the proper nutrients are there to support these processes.

There are 3 Main Energy Systems

 We couldn’t spend all this time speaking about energy without quickly mentioning the body’s 3 energy systems! The energy systems we’re talking about refer to the ways in which energy is produced by the body. The first system is called the phosphagen system, the second is the glycolytic system, and the third is the oxidative system, all of which work together to ensure that we are able to work, move, and live our lives. 

So what determines which energy system is used? They all function as the primary system at different times. The phophagen system is mainly used during short, explosive activity lasting roughly 30 seconds or less. Now, that’s not very long at all, which is why we have the glycolytic system. This system comes into play during activities lasting roughly 30 seconds to 3 minutes - like running up a set of stairs. For activities lasting longer than 3 minutes the oxidative system (which uses oxygen to help produce energy) helps you harness all the energy you need for those longer training sessions or endurance activities.

Best Foods To Boost Energy Levels

Our bodies are pretty amazing at extracting energy and nutrients from foods, but some foods are just better than others at supporting our health. Are you wondering which foods can give you more energy? Here are a few of our favourites! 

The first of our energy-giving foods are nuts and seeds. These convenient, tasty treats are jam-packed with protein, carbs and healthy fats which help to fight fatigue and inflammation all while providing sustained energy. Fatty fish (like salmon, herring, and trout) also contain protein and healthy fats like omega-3’s which can be particularly helpful in fighting fatigue and feeling energized! 

Next on our list would be leafy greens, which are loaded with vitamins and minerals that support our enzymes and energy production processes. Whole grains also make our list of energy boosting foods due to their high carbohydrate content. The special thing about whole grains though, is that they’re often high in protein as well as fibre, which allows for a slow release of glucose into our bloodstream so that we don’t feel a post-meal sugar crash. 

Although our next item isn’t necessarily a food, we couldn’t leave water off of our list of best foods for energy. Water is an absolute necessity for life - it’s involved in many reactions and cellular processes throughout the entire body including energy production! In fact, when we’re dehydrated body processes tend to slow down leaving us feeling sluggish and tired. For a good pick-me-up, water is a great option any time of day!

The body uses energy every second of every day. We need energy to live, and our bodies are so creative in the ways that we can not only consume, but also transform and use energy to support our lives and daily activities. Making sure that we’re eating nourishing foods, supporting our systems with pure, safe, and effective supplements, and enjoying regular movement are all crucial to supporting our energy levels. If you’re feeling tired or need an extra boost of energy, Aarja Health has an entire collection of some of the best supplements to support energy levels. Be sure to check it out in our shop! In the meantime, stay healthy!