What are the three components of energy expenditure quizlet?

January 1, 2026 •

4 min read

According to the National Institutes of Health, a person's total daily energy expenditure is composed of three main factors, the largest of which is typically the resting metabolic rate. Understanding these three components can provide valuable insight into how the body uses energy and can inform more effective strategies for weight management and overall health.

Quick Summary

Total daily energy expenditure is composed of the basal metabolic rate, the thermic effect of food, and physical activity, all of which contribute to the total calories burned throughout the day. The relative proportion of each component varies depending on individual factors like body composition and lifestyle. These three elements form the basis for calculating a person's daily caloric needs.

Key Points

Three Key Components: Energy expenditure consists of Basal Metabolic Rate (BMR), the Thermic Effect of Food (TEF), and physical activity.
BMR is the Largest Factor: Your BMR is the energy your body uses at complete rest for basic functions and is the most significant portion of your daily calorie burn.
TEF is for Digestion: The thermic effect of food accounts for the energy needed to process, digest, and store nutrients from the food you eat.
Physical Activity Varies Most: The energy used for physical activity is the most variable component, including both structured exercise and non-exercise movement.
Macronutrients Affect TEF: Protein requires significantly more energy to process than carbohydrates or fats, thereby increasing TEF.
Increase Energy Expenditure: Boosting your energy output can be achieved by building muscle (to increase BMR) and increasing physical activity (both exercise and NEAT).
Effective Weight Management: A comprehensive approach to weight management involves understanding and influencing all three components of energy expenditure.

The Three Pillars of Your Metabolism

Your body continuously burns calories, even when at rest. This process is known as total daily energy expenditure (TDEE). The three core components—basal metabolic rate (BMR), the thermic effect of food (TEF), and physical activity—are the foundation of TDEE. Understanding how each component contributes to your overall energy balance is crucial for managing your weight and optimizing your health. The widely referenced learning platform, Quizlet, often presents these three components in flashcard format for quick and easy study, reinforcing their importance in nutrition and exercise science.

Basal Metabolic Rate (BMR)

Basal metabolic rate is the energy your body expends while at complete rest to maintain essential life-sustaining functions. This includes critical processes such as breathing, blood circulation, temperature regulation, and cell production. For most people, BMR is the single largest component of TDEE, accounting for 60% to 75% of total calories burned. Several factors influence your BMR, including:

Body Composition: Individuals with a higher proportion of lean muscle mass have a higher BMR, as muscle tissue is more metabolically active than fat tissue.
Body Size: Larger individuals require more energy to support their body's functions, leading to a higher BMR.
Age: BMR generally decreases with age. After age 20, it typically drops by about 3-5% per decade.
Sex: Men generally have a higher BMR than women due to a higher average muscle-to-fat ratio.

The Thermic Effect of Food (TEF)

Another key component of energy expenditure is the thermic effect of food, also known as diet-induced thermogenesis (DIT). This is the energy required to digest, absorb, transport, and metabolize the food you consume. TEF accounts for approximately 10% of your total daily energy expenditure, though this percentage can vary based on the types of food you eat.

Different macronutrients have varying thermic effects:

Protein: Has the highest thermic effect, requiring 20-30% of its energy content for digestion.
Carbohydrates: Have a moderate thermic effect, using 5-10% of their energy.
Fats: Have the lowest thermic effect, typically requiring only 0-3% of their energy for processing.

Physical Activity

The most variable component of energy expenditure is physical activity, which includes all energy burned through movement. This can be broken down into two sub-components:

Thermic Effect of Activity (TEA): This covers the energy used for planned, purposeful exercise, such as running, weightlifting, or playing sports.
Non-Exercise Activity Thermogenesis (NEAT): NEAT is the energy expended for everything we do that is not sleeping, eating, or sports-like exercise. It includes daily movements like fidgeting, walking to the car, and performing household chores. For sedentary individuals, physical activity may account for only 15% of TDEE, while for highly active individuals, it can be as much as 50%.

Comparison of Energy Expenditure Components


Feature	Basal Metabolic Rate (BMR)	Thermic Effect of Food (TEF)	Physical Activity (PA)
Contribution to TDEE	Largest component (60–75%)	Smallest component (~10%)	Most variable (15–50%+)
Function	Energy for fundamental bodily processes at rest	Energy for digestion and metabolism of food	Energy for all voluntary and non-voluntary movement
Variability	Relatively stable, influenced by genetics, age, sex, body composition	Modest variability, dependent on macronutrient composition and meal size	High variability, dependent on activity level, duration, and intensity
Influencing Factors	Lean muscle mass, body size, age, genetics	Protein intake, fiber content, meal size, meal frequency	Exercise habits, daily movement, lifestyle choices
Ways to Increase	Building muscle mass through strength training	Consuming a higher proportion of protein and fiber	Increasing exercise intensity, duration, and NEAT

Optimizing Your Energy Balance

To effectively manage your weight, you must understand how these three components combine to form your total energy output. A successful strategy often involves manipulating the two most variable factors: physical activity and the thermic effect of food. While you can't significantly alter your BMR in the short term, consistent lifestyle changes can increase your energy expenditure over time.

For instance, incorporating high-intensity interval training (HIIT) can increase your physical activity output substantially. Similarly, increasing your intake of lean protein can boost your TEF, meaning more energy is burned during digestion. Meanwhile, increasing non-exercise activity, such as taking the stairs or standing while you work, can add up to a significant daily calorie burn. Combining these strategies with a balanced diet is the most effective approach to achieving sustainable results.

Conclusion

In summary, the three components of energy expenditure—basal metabolic rate, the thermic effect of food, and physical activity—provide a comprehensive framework for understanding how your body uses calories. BMR is the foundational, largest, and most stable component, representing the energy required to simply exist. TEF, while a smaller portion, can be influenced by dietary choices, particularly protein intake. Finally, physical activity is the most dynamic and controllable factor, offering the greatest potential for increasing daily calorie burn through both structured exercise and daily movement. By intelligently adjusting your physical activity and nutritional intake, you can effectively manage your overall energy expenditure to meet your health and fitness goals. For further information, consider reading resources from reputable sources like the National Library of Medicine, which extensively covers energy expenditure research.

Sources:

Johnstone AM, et al. Factors influencing variation in basal metabolic rate... Am J Clin Nutr 2005; 82: 941-948. (Note: This is a specific reference to a study and not the NCBI article itself)
National Center for Biotechnology Information (NCBI). Factors Affecting Energy Expenditure and Requirements. https://www.ncbi.nlm.nih.gov/books/NBK591031/
Examine.com. Thermic effect of food (TEF). https://examine.com/outcomes/thermic-effect-of-food/

Frequently Asked Questions

The largest component is the basal metabolic rate (BMR), which accounts for 60% to 75% of your total daily energy expenditure for most people.

Diet influences TEF through its macronutrient composition. Protein has the highest thermic effect, meaning your body burns more calories digesting it compared to carbohydrates or fats.

While often used interchangeably, BMR (Basal Metabolic Rate) is the minimum energy needed for essential body functions at complete rest. RMR (Resting Metabolic Rate) is slightly less restrictive and is measured in a relaxed state.

Yes, you can increase your BMR primarily by increasing your lean muscle mass through strength training exercises. Muscle tissue is more metabolically active than fat tissue.

NEAT stands for Non-Exercise Activity Thermogenesis, which is the energy expended for everything other than sleeping, eating, or intentional exercise. It includes daily movements like fidgeting and walking, and can significantly impact total energy expenditure.

While it is possible to estimate all three components using formulas and activity multipliers, precise measurements typically require laboratory methods like indirect calorimetry. For most purposes, estimates provide a useful baseline.

Knowing the three components is important for managing energy balance and achieving weight goals. It allows for a more comprehensive strategy than simply focusing on exercise or diet alone, helping you make informed decisions about nutrition and activity levels.

Age decreases TDEE as BMR naturally slows, often due to a loss of muscle mass. Sex affects TDEE because men generally have a higher muscle-to-fat ratio and larger body size, leading to a higher BMR than women.