In this article we discuss the key concepts for understanding energy expenditure and the calories you need each day to maintain, lose, or gain body weight. 

By Dr. Adam M. Gonzalez
SHIFTED’s Chief Scientific Officer

The calories in-calories out model of weight loss seems like a simple math problem on the surface.  Just burn more calories than you consume, and you’ll lose weight, right? 

While that is true, it is quite complex in the real world because of the dynamic nature of energy expenditure.   This article will help you understand the components of energy expenditure and how to estimate your calorie needs to maintain, lose, or gain body weight. 

Key Points: 

• The calories-out part of the equation is complicated and somewhat of a moving target.
• The components of energy expenditure consist of resting metabolic rate (RMR), thermic effect of food (TEF), exercise activity thermogenesis (EAT), and non-exercise activity thermogenesis (NEAT).
• While it is impossible to accurately measure all these components, prediction equations can be used to determine maintenance calories.
• With an understanding of the goal of weight maintenance, loss, or gain, you will be able to estimate calorie intake recommendation.

Components of energy expenditure

The calories-in part of the equation is simple – it’s the amount of food calories consumed.  The calories-out part of the equation, however, is complicated and somewhat of a moving target.

Understanding the components of energy expenditure will help shed some light on why it is difficult to accurately measure and how to estimate your maintenance calories.  Total daily energy expenditure can be broken down into four distinct contributors towards “burning calories”.  These components consist of :

• resting metabolic rate (RMR)
• thermic effect of food (TEF)
• exercise activity thermogenesis (EAT)
• non-exercise activity thermogenesis (NEAT) [4].  

Resting metabolic rate (RMR)

RMR makes up the largest component of daily energy expenditure (~70%) and consists of the energy required to maintain bodily function at rest.  Naturally, this value will vary greatly between individuals depending on many factors including sex, height, age, body composition, lean body mass, genetics, and training status. 

Thermic effect of feeding (TEF)

TEF (sometimes called dietary thermogenesis) refers to the bump in energy expenditure (above RMR) that occurs for several hours after ingestion of a meal because of the energy that is required for digestion and absorption.  The contribution of TEF towards daily energy expenditure is estimated to be approximately 10%. 

Just by changing the types of foods that you eat, you can alter the calories out part of the equation through TEF because it is effected differently by the three macronutrients (protein ~20%; carbohydrates ~10%; and fat ~3% of the calories consumed). 

Since protein has the largest effect on TEF, higher protein diets may positively impact energy balance, and this is one of the reasons why a high-protein diet is recommended for weight loss and maintenance.

Exercise activity thermogenesis (EAT)

EAT refers to the energy expended during your planned exercise sessions.  Contrary to what most active individuals may think, it is only estimated to contribute approximately 5% of daily energy expenditure.  Notably, EAT will certainly vary between individuals based upon the volume of exercise performed, but it’s probably not as much of a contributor as you may have thought. 

Non-exercise activity thermogenesis (NEAT)

NEAT is the energy expended during day-to-day activities – pretty much anything that isn’t structured exercise.  This can include movements ranging from subconscious fidgeting, walking to your car, or occupational movement. 

Generally, NEAT is estimated to account for approximately 15% of total daily energy expenditure.  Similarly, NEAT can vary greatly between individuals depending on how active you are.  For example, NEAT can contribute almost nothing for an extremely sedentary person whereas it can contribute up to 50% of total daily energy expenditure in extremely active individuals [4]. 

Of the four components, NEAT seems to be the most variable from person to person and within the same person at different times.  It has been shown that when people restrict calories (i.e., go on a diet) or start a new workout plan, NEAT tends to spontaneously drop.  In other words, you simply move less, and large reductions in NEAT during periods of dieting may hinder weight loss [3]. 

For example, it is possible reducing your calorie intake by 300 calories will not result in weight loss because this can be offset by 300 less calories being burned through NEAT. 

Determining maintenance calories

Maintenance calories are the amount of energy intake required to maintain your current body weight.  In theory, your maintenance calories match your total daily energy expenditure and would be the sum of RMR, TEF, EAT, and NEAT.  As you can imagine, these are difficult to pinpoint and get an exact value.  Fortunately, there are several equations that provide an estimate of maintenance calories based upon body characteristics and physical activity status.  While this approach is well accepted as a starting point, be aware that there can be a considerable amount of error and it is just getting you in the ballpark with an estimation. 

First, apply your information to one of the common equations below to estimate RMR: 

*FFM=fat-free mass

Next, you need to multiply that value by a correction factor based on physical activity status:

Again, it is important to note that this math will provide an estimation of maintenance calories and you will need to individualize and fine tune with trial-and-error. Also, maintenance calories are a “moving target” when you go on a diet because body weight, RMR, and NEAT may decrease. 

Setting calories to lose weight

It is generally recommended to lose no more than 0.5 to 1% of body mass per week [2, 6].  For most, this will equate to approximately a 10-20% energy deficit (i.e., multiplying maintenance calories by 0.9-0.8). 

Indeed, more aggressive calorie cuts will promote more rapid weight loss, but at the expense of elevated hunger, unfavorable metabolic adaptations, and low sustainability.  Cutting over 500 Calories per day from maintenance calories also seems to increase the risk of losing a greater percentage of muscle mass as compared to fat mass [5]. 

Again, since calories-out is a “moving target”, you will inevitably need to continue reducing calories in a stepwise fashion to maintain a calorie deficit required for sustained weight loss.  For example, as weight loss occurs, RMR, TEF, EAT, and NEAT all drop as well.  

Setting calories to gain weight

I imagine you want to gain muscle, right?  To maximize muscle growth with resistance training, a caloric surplus is required.  However, increasing calories too much will inevitably lead to excessive fat gain. 

Since a new lifter has a greater potential for muscle growth, they can be more aggressive with adding extra calories (20-40% above maintenance calories; ~500-1000 Calories per day). 

If you have years of lifting under your belt, you probably don’t have the capacity to rapidly build muscle and you may be more prone to fat gain from such a caloric surplus.  Therefore, modest increases (10-20% above maintenance calories; ~250-500 Calories per day) seem appropriate for a more advanced lifter [1]. 

Similar to weight loss, the calories-out side of the equation can also be affected by increasing calories.  For example, RMR and NEAT may increase when overfeeding.  Therefore, this will require some trial-and-error as well.  

About the Author

Adam M. Gonzalez is an associate professor in the Department of Allied Health and Kinesiology at Hofstra University.  He earned a Ph.D. in Exercise Physiology from the University of Central Florida in 2015 and holds certifications as a Certified Strength and Conditioning Specialist (CSCS), along with a Certified Sports Nutritionist Certification (CISSN). 

His primary research interests include exercise and nutritional strategies to optimize body composition, maximize health, and enhance adaptations to exercise.  He was also awarded the 2022 Nutritional Research Achievement Award by the National Strength and Conditioning Association.

References

[1] Aragon A. A.; Schoenfeld B. J. Magnitude and composition of the energy surplus for maximizing muscle hypertrophy: implications for bodybuilding and physique athletes. Strength & Conditioning Journal 2020, 42, 79-86.   https://journals.lww.com/nsca-scj/Abstract/2020/10000/Magnitude_and_Composition_of_the_Energy_Surplus.9.aspx

[2] Helms E. R.; Aragon A. A.; Fitschen P. J. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition 2014, 11, 1-20.  https://pubmed.ncbi.nlm.nih.gov/24864135/

[3]  Levine J. A. Non-exercise activity thermogenesis (NEAT). Best Practice & Research Clinical Endocrinology & Metabolism 2002, 16, 679-702.  https://pubmed.ncbi.nlm.nih.gov/12468415/

[4] Martínez-Gómez M. G.; Roberts B. M. Metabolic Adaptations to Weight Loss: A Brief Review. Journal of Strength and Conditioning Research 2021. https://pubmed.ncbi.nlm.nih.gov/33677461/

[5] Murphy C.; Koehler K. Energy deficiency impairs resistance training gains in lean mass but not strength: A meta‐analysis and meta‐regression. Scandinavian journal of medicine & science in sports 2022, 32, 125-137.  https://pubmed.ncbi.nlm.nih.gov/34623696/

[6]  Roberts B. M.; Helms E. R.; Trexler E. T.; Fitschen P. J. Nutritional recommendations for physique athletes. Journal of human kinetics 2020, 71, 79. https://pubmed.ncbi.nlm.nih.gov/32148575/