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Energy and Exercise

All about Energy and Energy Metabolism

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All About Energy and Energy Metabolism

We know that working out requires energy. We also know that some sources of energy are better than others. But, for many of us, that’s about it.

Knowing more about energy metabolism – how your body takes in, stores, and uses energy – can help you build a better diet and a better workout.

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A Quick Note on Energy

We won’t take too deep of a dive into how energy metabolism works at the molecule level. But, we’ll be breaking out some dietary terms later on that build on this base. So, a quick introduction to how energy comes from is warranted.

You may remember from grade school science that the world – including your body – is made up of atoms and molecules. 

When these bond together to form molecules and macromolecules, energy is stored. When molecules and macromolecules are broken down into atoms and molecules, energy is released. (Dunford & Doyle, p. 34).

Natural Sugars

Energy in the Diet

In a pinch, the body can break down all kinds of things for energy, including protein. However, the body’s main source of energy is sugar.


“Sugar” is more of a chemical term than a cooking term. The “sugar” you think of is one example, but it helps to think of sugar as a kind of substance rather than just table sugar. Table sugar, and other simple sugars, like from fruits are good examples, but they’re just that.

Carbohydrates (and Calories)

Your body can also get sugar by digesting carbohydrates (Brink, p. 29). If you’re big into diet, you might be a bit confused by this. Your body gets sugars by breaking down carbohydrates, but sugar has carbohydrates?

It’s okay to be confused. There’s kind of a terminology mixup happening regarding the use of the word “carbohydrate.” In chemistry, “carbohydrate” is a kind of structure that yields energy when broken down. In nutrition, “carbohydrate” is also used as a measure of how much energy is in a food. 

“Calorie” is also a measure of how much energy is in a food. However, because your body can break down things other than carbohydrates for energy, it’s possible for a food to have calories without having carbs. I know, it’s confusing.


On the note that your body can break down things other than carbs for energy, let’s talk about fat. You already know – though you might take for granted – that fat exists in your body and in your diet. This is another kind of naming mixup.

“Fat” is another chemical structure. Your body creates it as a way of storing energy that you took in but didn’t use. Animals and some plants also do this and you may eat those plants and animals.

There’s a common misconception  that eating fat makes you fat. Fat is an energy yielding nutrient. So, fat in your diet is energy that you will have to burn through exercise if you don’t want to store it. Still, it’s not a one-to-one ratio.

Other Sources

Because the article is called “All about Energy,” let’s talk about two more energy yielding nutrients.

Protein is an energy yielding nutrient, though there are things that the body would rather do with it. Protein is an important building block of muscle, so in some ways consuming it for energy is a bit of a waste. Further, energy metabolism of protein releases acids that some doctors believe may be harmful (ibid, p. 20). However, in some aerobic activities like running, up to 20% of energy metabolism can be the breakdown of proteins (Bagchi et al, p. 189).

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Energy Metabolism

How your body uses energy is called “energy metabolism.” Some people have a “high” or “fast” metabolism, meaning that they burn energy at a high rate. Other people have a “low” or “slow” metabolism, meaning that they burn energy at a low rate.

Like many health factors, metabolism is partially genetic and partially due to diet and lifestyle factors. 

Hormone Metabolism

Hormones and Energy Metabolism

A person’s energy metabolism has a lot to do with hormones, so some hormone imbalances beyond their control can impact how their bodies use or store energy.

Hormones don’t only control how the body uses energy, they control how the body demands energy. One hormone, Leptin, is released by fat and makes us feel full and satisfied. That’s one of the reasons why fatty food can make us feel full and satisfied.

However, Leptin is also released by body fat. Some doctors believe that having more body fat can lead to so much Leptin in the system that the body stops reacting to it and it becomes increasingly difficult for the brain to feel satisfied with food.

A similar relationship involves Insulin. Insulin controls how the body carries out energy metabolism involving a specific kind of sugar called “glucose.” People with Insulin imbalances may store too much glucose and accumulate body fat. They may also burn glucose too quickly and have problems maintaining a healthy weight.

Metabolism Energy

When and Where Energy Metabolism Happens

A good workout can use up a lot of energy. However, your body is always using energy. Digesting food, pumping blood, breathing, they all take energy. Not a lot. But, when you remember that these systems never stop, they add up. In fact, energy metabolism of this kind (called resting metabolic rate) accounts for up to 75% of daily energy metabolism (Brink, p. 49).

Similarly, another category of energy metabolism has to do with non-exercise activity. This category, sometimes called “Activities of Daily Living” is often taken for granted, it can account for at least a fifth of the average person’s daily energy metabolism (Dunford & Doyle, p. 75).

As for how much energy metabolism exercise is responsible for, that’s a difficult question. How much various people exercise can be drastically different. Further, different kinds of exercise have different energy metabolism requirements and even go about energy metabolism in different ways.

Energy Metabolism Facts Boosters

Tools for Maximizing Energy Metabolism

All of this information about where energy comes from and how the body uses it can be a lot to handle. Fortunately there are a couple of tools that can help you manage it.

Energy Balance Equation

The Energy Balance Equation

How we use and take in energy and how it relates to our health can be easily visualized through the energy balance equation (Brink, p. 48). 

Simply put, when you take in more energy than you burn, your body stores that energy as fat and you gain weight. Alternatively, when you use more energy than you take in, your body burns energy stored in fat and you lose weight.

The energy balance equation is handy, but it’s also a bit too simple for our purposes. For one thing, it reduces all food to just a caloric value. Further, it fails to take weight gain from muscle growth into account. Fortunately, there’s another tool, valuable on it’s own but even more useful when paired with the energy balance equation.

Macro Calculators

Macro Calculators” are named for “Macronutrients” – those that should make up the largest parts of our diets. They work on similar principles to the energy balance equation but are a lot more nuanced. Good ones factor in different food types as well as user info like age, activity level, and even fitness goals.


Energy Metabolism for Muscle Gain

Understanding and maximizing your diet and routine for muscle building can be difficult. Too much or too little dietary energy for your activity level, and you’re in for trouble.

Fortunately, as long as you have a general understanding of how to balance energy intake and expenditure, you should be okay. This article is a great place to start but dive into those links, check out our recommended reading below, and never be afraid to talk to your doctor if you have questions.

For Further Reading:

(Ed.) Bagchi, Debasis; Nair, Sreejayan; Sen, Chandan K. “Nutrition and Enhanced Sports Medicine: Muscle Building, Endurance, and Strength.” Academic Press. Waltham, MA. 2013.

Brink, Will. “Muscle Building Nutrition: Serious Lean Muscle Gains, without the Body Fat – Scientifically Proven.” Internet Publications. 2003.

Dunford, Marie & Doyle, J. Andrew. “Nutrition for Sport and Exercise.” Thomson Wadsworth. Belmont, CA. 2008.

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