Weight Loss Nutrition

The Science of Energy Balance: How it Factors Into Metabolism

Brad Dieter
Brad Dieter
| Stay Updated with NASM!

Energy balance is one of the most fundamental concepts in the context of health & fitness as it plays a central role in human health and human performance. It is a concept that applies to almost every aspect of health & fitness coaching: from nutrition coaching, personal training, strength & conditioning, and even sports coaching.A robust understanding of energy balance is critical. This article will lay the foundation for what energy balance is, how it relates to metabolism, and how it can be changed.

What is Energy Balance?

To cut straight to the point, as humans, we exist in the physical universe. So, no matter how complicated and crazy biology may seem, at the end of the day, our body’s follow the “laws” of physics. This means that, fundamentally, human beings are just a complex system of mass, which is where we walk into the concept of energy balance.

Energy balance is the concept that helps us understand how humans gain, lose, and maintain weight. It is based on one of the core concepts in physics, specifically, the concept of the law of conservation of energy.

The law of conservation of energy: Energy cannot be created or destroyed in an isolated system.

This means that as humans, all energy must be accounted for when it enters and leaves our body, and that any difference in net energy is accounted for. To break this down very simply, let’s look at three possible scenarios as it relates to energy in humans.

1) Energy going into the body > Energy leaving the body = The body has positive energy balance.

2) Energy going into the body < Energy leaving the body = The body has negative energy balance.

3) Energy going into the body = Energy leaving the body = The body has equal energy balance.

What Are the Types of Energy Balance?

Above we discussed a few concepts about energy balance and how you can be in positive, negative, or equal/perfect energy balance. Now, what exactly does that mean in the context of us as people in our daily lives?

Well, the simplest way to think about it is to think about how energy goes into our body and how it leaves our body. The energy that goes into our body is relatively simple to understand—it comes from the calories in the food that we consume.

The energy that leaves our body is a bit more complicated: it is a result of our basal metabolism (which gets really complicated) and any sort of physical activity we do that requires energy to accomplish. Energy that leaves our body is usually described as our Total Daily Energy Expenditure, or TDEE. In most people this TDEE is comprised of the following components:

Basal Metabolic Rate - the energy expended by your body tissues to just keep them alive and functioning

● Thermic Effect of Food - the energy it takes to process the food you consume

● Activity Thermogenesis - the energy you expended moving around, including both structured exercise and non-structured movement (e.g., walking place to place or doing chores)

These are the primary things that determine whether your body is in a positive, negative, or equal/perfect energy balance.


As mentioned above, when there is more energy going in than going out, you are in a state of positive energy balance. Being in a state of positive energy balance can be affected by both having too high of an intake or too low of an output, or a combination of both.

It is important to note that the relative amounts matter more than the absolute amounts.

A positive energy surplus can be created by creating a disparity between eating more calories than expended, which may come from very high calorie intake or very low energy expenditure.


Like a positive energy balance, negative energy balance is created when the energy mismatch goes the opposite direction: more energy is expended than is going in. The energy that the body utilizes at this point is stored energy in the form of stored carbohydrates, stored fats, or stored proteins.

Perfect Balance

Perfect energy balance occurs when the energy coming in and the energy expended are perfectly matched. In reality, this is very difficult to do over very short time frames (e.g. being in perfect balance in a given day), but is relatively easy to accomplish over periods of weeks or months. Therefore, many people stay weight stable for years at a time.

Energy Balance Equation: How to Measure Energy Balance

Perhaps the most effective way to assess energy balance is to track body weight over extended periods of time (think weeks or months, not days). Body weight can fluctuate substantially during a given day or week due to hydration status, glycogen status, and other variables, but the average weight over several weeks or months is an excellent indicator of the state of energy balance a person is in.

If body weight is increasing over the span of weeks or months, that person is in positive energy balance. Conversely, if body weight is increasing over the span of weeks or months, that person is in negative energy balance. If someone is weight stable over that timeframe, they are equal/perfect energy balance.

There are many ways to measure energy balance, some being far more intricate and complicated than others. There are laboratory measurements such as metabolic chambers and doubly labeled water which can be very accurate but are impractical for almost all settings except in scientific studies.

What Does Energy Balance Have to Do with Metabolism?

Energy balance and metabolism are linked, but their relationship is not as quite forward as most people might think.

In one sense, metabolism has a direct influence over energy balance. If your TDEE is either very high or very low, the likelihood of you being in perfect energy balance is very unlikely. For example, athletes who expend 7,000-10,000 calories per day during peak training seasons often find it hard to stay in energy balance as eating 10,000 calories a day can be very difficult.

Conversely, individuals who are very sedentary and only expend a total of ~1,500 calories per day often find themselves in a state of positive energy balance and keeping intake that low consistently can be very difficult.

In another sense, energy balance can affect metabolism as well. This is often a very misunderstood phenomena and people often will refer to this as “starvation mode”. But in reality, the state of energy balances a person is in does affect their TDEE quite a bit, but not really their resting metabolic rate.

For example, if an individual is in a state of positive energy balance their total expenditure goes up to try and balance that out. However, this increased expenditure comes almost entirely from increasing their non-exercise activity. The opposite is also true. In the context of a negative energy balance, energy expenditure goes down to try and balance it out, with most of that drop coming from a reduction in physical activity.

Read also: 5 Things to Know About Your Metabolism

Why is Energy Balance Important?

Energy balance is important for several reasons, but the two main reasons are for maintaining health and for maximizing performance. Whenever energy balance is substantial out of “equilibrium,” health and performance suffer.

When individuals are in a state of positive energy balance for extended periods of time, the extra energy is stored primarily as body fat. Over time this results in increased adiposity and carries with it substantial health risks such as cardiovascular disease, diabetes, hypertension, and other chronic diseases.

When individuals are in a state of negative energy balance for extended periods of time, the energy debt they have is paid for by the tissues in their body. This often results in impaired performance and an increased risk of injuries such as stress fractures, tendon and ligament damage, and other injuries. Athletes should strive to be in perfect energy balance or very small surpluses during most of their careers, with some short periods of energy deficits whenever it is necessary to lose body weight or body fat.

How to Change Your Energy Balance

Fundamentally there are three main ways that a person can safely and effectively change one’s energy balance:

1. Change food intake. Either increasing or decreasing food intake changes how much energy a person is taking in.

2. Change their amount of structured exercise. People can change how much they engage in structured exercise in several ways. They can change how frequently they exercise; they can change how long their training sessions are, or they can change the intensity of those training sessions. Each approach can help alter energy expenditure.

3. Change their non-exercise activity. The non-exercise activity a person engages in often has the biggest effect on the energy output. Walking more, doing more chores, taking the stairs, etc., are all effective ways to increase energy output. Conversely, having a more sedentary life substantially reduces energy output.

The Author

Brad Dieter

Brad Dieter

Brad is a trained Exercise Physiologist, Molecular Biologist, and Biostatistician. He received his B.A. from Washington State University and a Masters of Science in Biomechanics at the University of Idaho, and completed his PhD at the University of Idaho. He completed his post-doctoral fellowship in translational science at Providence Medical Research Center, Providence Sacred Heart Medical Center and Children’s Hospital where he studied how metabolism and inflammation regulate molecular mechanisms disease and was involved in discovering novel therapeutics for diabetic complications. Currently, Dr. Dieter is the Chief Scientific Advisor at Outplay Inc and Harness Biotechnologies, is co-owner of Macros Inc and is active in health technology and biotechnology. In addition, he is passionate about scientific outreach and educating the public through his role on Scientific Advisory Boards and regular writing on health, nutrition, and supplementation. Want to learn more in Brad's areas of expertise? Check out his NASM product recommendations.


Start Your Fitness Career Today

Become A Top-Notch Certified Personal Trainer

A NASM advisor will contact you to help you get started.

Get Started