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Losing Weight Using The Energy Balance Equation

The overweight/obesity trend in the United States has been increasing at an alarming rate over the past few decades. Approximately 61% of Americans are overweight and almost 26% are obese! These obesity rates do not apply as much to endurance athletes but many endurance athletes do face weight issues. This article will provide you with some background knowledge of how to change your weight using an old, well-known method with new information on how to effectively use it to lose, gain or maintain your weight.

For years health professionals have developed weight management programs that included the necessary components for successful weight management-behavior change, nutrition education, and exercise prescription-yet the overweight/obesity trend continues to rise. Why haven’t these popular weight management programs worked?

The reason is because they are missing one key component-a person’s individual metabolism. The foundation of any successful weight management program must be centered on a person’s individual metabolic rate and the energy balance equation for long-term success. The energy balance equation may be a new term for you but you certainly know the concept–calories in versus calories out. (See the graphic at the end of this article for a visual explanation of the energy balance equation.)

What is The Energy Balance Equation

the energy balance equation

More specifically, if you want to lose weight, you must be in negative energy balance (calories in < calories out). If you want to gain weight, you must be in positive energy balance (calories in > calories out). And if you want to maintain your weight, you must be in stable energy balance (calories in = calories out).

The concept is so simple to understand but it is so hard to do because we don’t understand all of the pieces of the equation and don’t know how to put them together to change our weight. Until now! Let’s take an in-depth look at this concept in order to understand how to better use it.

Breaking Down the Energy Balance Equation

The energy balance equation has two sides: the calories in (consumption) and calories out (expenditure). The calories in side is made up of carbohydrates, protein, and fat. This side of the equation is very simple to understand because it is only affected by the amount of food you eat. We all know, or can figure out pretty easily, how many calories we eat.

The calories out side is much more complicated because biology has more of an impact on each component, which makes it more difficult to balance and manage. It is made up of the thermic effect of feeding, the thermic effect of physical activity, and resting metabolic rate.

The Thermic Effect of Feeding (TEF)

The thermic effect of feeding (TEF) is approximately 10% of total metabolism and includes obligatory thermogenesis (the result of the energy-requiring processes of digesting and absorbing food) and facultative thermogenesis (the activation of the sympathetic nervous system and its stimulating effect on metabolism). The TEF can vary greatly depending on both the quantity and type of food eaten. TEF is usually not a primary factor in changing body weight because of its low relative amount of contribution to total metabolism.

Thermic Effect of Physical Activity (TEPA)

The thermic effect of physical activity (TEPA) is approximately 15-30% of total metabolism and includes occupational and lifestyle activity (what you do at work, running errands, etc.), and purposeful exercise (training). This is the most variable component and can contribute significantly to weight loss and weight gain. More exercise=more calories burned=more weight lost (if you control the amount of calories you eat). This is what many of you experience when you first begin training–you lose weight because you are burning more calories than you are eating.

Resting Metabolic Rate (RMR)

Resting metabolic rate (RMR) is approximately 60-75% of total metabolism and includes sleeping metabolism, basal metabolism, and arousal metabolism. RMR is the amount of calories your body burns at rest to perform basic functions such as your heart beating and your brain functioning. RMR is the most important component on the calories out side of the energy balance equation because it represents up to ¾ of the total calories burned by the body.

Why Fad Diets Don’t Work

Now that you have a good understanding of what the energy balance equation is and its different components, let’s talk about why fad diets don’t work and why 95% of people who go on diets regain the weight they lost and more back in 1-2 years.

The reason is because they all address the same factors-exercise, nutrition, and behavior change. Not one of these fad diets accounts for a person’s individual metabolism or if they do, they estimate it. How would you like to go into your doctor’s office and have your blood pressure estimated?

This is like flipping a coin to decide if you have high or low blood pressure-you’ll be right half of the time! But since we can measure blood pressure easily, there is no need to estimate it.

The same thing applies to RMR. Estimating RMR based on equations could be very inaccurate and detrimental to your health.

In fact, one research study, conducted at the University of Pennsylvania in 1988, predicted and measured the RMR of 80 females of the same height and weight. The researchers found a variance of approximately 500 calories between the predicted and measured RMR’s. Because RMR can represent up to 75%, a 500-calorie inaccuracy automatically sets a person up for failure before they even begin a program. Eating 500 calories more per day adds up to a 52-pound weight gain in 1 year! No wonder our society is gaining weight.

You Must Measure RMR

Since the number one factor that influences RMR is body mass, a loss of body weight will decrease a person’s RMR, and vice versa.

When you lose weight, your RMR also decreases. This is the explanation for the infamous “yo-yo” dieting phenomenon that happens with people trying to lose weight-they decrease the amount of calories they eat, they may exercise a little, and voila!, they lose weight. But their RMR decreases because they are now at a lower body weight, which isn’t a big deal except when that person looks in the mirror, likes what they see from the weight they have lost, and decides to celebrate by eating a couple of cookies, or going out for drinks with friends.

This person is now increasing the amount of calories they eat each day and guess what? Their new, lower RMR has a hard time catching back up to support this new increased calorie balance and since it cannot catch up, the person begins to gain weight again.

You Must Measure RMR Consistently

Therefore, the key factor that will determine success with any type of body weight goal is measuring resting metabolic rate frequently in order to accurately provide you with the correct amount of calories you need to eat and the amount of exercise you need to perform in order to reach your weight goals. .

Having your RMR measured on a consistent basis with weight loss or gain is the most important thing you can do to succeed in changing how much you weigh.

I cannot stress enough how important it is to get your new RMR measured whenever you lose or gain a significant amount of weight (5-10 pounds). Even with a loss of 5-10 pounds, your body will require fewer or more calories to maintain itself, which makes it so crucial to readjust the energy balance equation and how many calories you are eating and burning.

For example, in a recent 12-week weight loss study, subjects lost 17 pounds and their RMR’s decreased by 125 calories. The researchers constantly re-adjusted the amount of calories the subjects ate based on their new RMR’s at each 4-week interval. If they hadn’t done this, the subjects would not have lost weight and in fact, would have gained weight over this small time period.

How Do You Measure Your RMR?

The easiest way to measure resting metabolic rate is by having the amount of oxygen you breathe in and breathe out (oxygen consumption or VO2) measured with an indirect calorimeter. This is a very noninvasive test. In fact, you simply breathe into an instrument from 5-30 minutes. After your VOis measured, your RMR in calories per day can be determined. All indirect calorimeters can measure VO2 and provide resting metabolic rate in calories per day. Look for this type of testing in human performance labs, hospitals, and some fitness centers.

What’s the Bottom Line?

The key to weight management is not following a certain fad diet or banning certain foods. The key is to measure the amount of oxygen you consume to determine RMR so you can accurately determine how many calories you should eat to either lose, gain, or maintain your weight. When your body weight is changing, be sure to have your RMR determined again in order to readjust your personal energy balance equation. It may sound a little complex but


·       McArdle, Katch & Katch. (1996). Exercise Physiology: Energy, Nutrition, and Human Performance. Fourth Edition.

·        Foster, G. et al. (1988). Resting Energy Expenditure, Body Composition, and Excess Weight in the Obese. Metabolism, 37(5), 467-472.

·         Alexander, H.A. et al. Efficacy of a Resting Metabolic Rate Based Energy Balance Prescription in a Weight Management Program Obesity Research, Presented at Nutrition Week Conference, 2002.

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Bob Seebohar, MS, RD, LD/N, CSCS
Bob Seebohar, MS, RD, LD/N, CSCS

Bob Seebohar is a Registered Dietitian specializing in sports nutrition for endurance athletes.  He is also an exercise physiologist and USA Triathlon Certified Level III Elite Coach.  Bob has completed over 100 endurance events including five Ironman races, the Boston Marathon, the Leadville 100 mile mountain bike race and the Leadville 100 mile trail run.  He was also a member of the 1996 US National Duathlon Team and competed in the World Championships in Ferrara, Italy.  He is also the author of the book, “Nutrition Periodization for Endurance Athletes: Taking Sports Nutrition to the Next Level” (Bull Publishing, 2004).

Bob provides sports nutrition consulting and coaching to all ages, types and abilities of endurance athletes. 


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