What Contributes the Most to Energy Expenditure?

November 1, 2025 •

3 min read

The average person's body uses between 60-70% of its total energy just to maintain basic life-sustaining functions at rest. This massive portion of your total daily energy burn is a key part of understanding what contributes the most to energy expenditure and is known as the Basal Metabolic Rate (BMR).

Quick Summary

This article explores the three main components of total daily energy expenditure (TDEE): Basal Metabolic Rate (BMR), the Thermic Effect of Food (TEF), and physical activity. It details how BMR is the largest factor, while lifestyle choices and body composition also play significant roles in your overall metabolism.

Key Points

Basal Metabolic Rate (BMR) is the biggest factor: BMR accounts for 60-70% of your total daily energy expenditure (TDEE), covering the calories needed for essential bodily functions at rest.
Physical activity is the most variable component: The calories you burn from movement can fluctuate wildly, with Non-Exercise Activity Thermogenesis (NEAT) representing a surprisingly large and controllable portion for many people.
Body composition affects your metabolism: People with more lean muscle mass have a higher BMR because muscle tissue burns more calories than fat, even at rest.
Diet influences calorie burn: The Thermic Effect of Food (TEF) is the energy used for digestion, with protein requiring the most energy to process, followed by carbohydrates and then fats.
Increase your metabolism through activity: While BMR is fundamental, boosting your NEAT—by taking the stairs, standing more, or fidgeting—is an effective way to increase your daily calorie burn.
Manage your lifestyle for maximum effect: Sustainable weight management depends on understanding how all three components—BMR, NEAT, and TEF—work together and how you can influence them through your daily habits.

Understanding Total Daily Energy Expenditure (TDEE)

Your body's total daily energy expenditure (TDEE) is the total number of calories you burn over a 24-hour period. Understanding TDEE is essential for effective weight management, whether your goal is to lose, gain, or maintain weight. This total is comprised of three main components: Basal Metabolic Rate (BMR), the Thermic Effect of Food (TEF), and Physical Activity. While all three play a role, their relative contributions can vary dramatically depending on your lifestyle and physiology.

Basal Metabolic Rate (BMR): The Biggest Contributor

The single greatest contributor to daily energy expenditure is your Basal Metabolic Rate (BMR). BMR represents the energy your body needs to perform its fundamental, life-sustaining functions while at rest, such as breathing, circulating blood, and regulating body temperature. For most people, BMR accounts for 60-70% of their TDEE. Factors influencing BMR include body composition (muscle burns more calories than fat), body size, age (BMR decreases with age), and gender (men typically have higher BMR).

The Thermic Effect of Food (TEF)

The Thermic Effect of Food (TEF) is the energy your body uses to digest, absorb, and metabolize the nutrients you eat. TEF accounts for about 10% of your total daily calorie burn. The amount of energy needed varies by macronutrient, with protein having the highest thermic effect (20-30%), followed by carbohydrates (5-10%), and then fats (0-3%).

Physical Activity: The Most Variable Factor

Physical activity is the most variable part of your energy expenditure. It includes Exercise Activity Thermogenesis (EAT), which is structured exercise like running, and Non-Exercise Activity Thermogenesis (NEAT). NEAT encompasses all other movement, such as walking, standing, and fidgeting. While EAT can provide a significant, temporary boost in calorie burn, NEAT can vary greatly between individuals, potentially differing by up to 2000 calories per day, and is a significant factor in overall TDEE, especially for active people.

BMR vs. NEAT: A Comparison


Feature	Basal Metabolic Rate (BMR)	Non-Exercise Activity Thermogenesis (NEAT)
Contribution to TDEE	60-70% of TDEE	Highly variable; 6-10% (sedentary) to 50%+ (highly active)
Dependence on Lifestyle	Less dependent; changes with age and body composition	Highly dependent; reflects daily routines and habits
Physiological Determinants	Body size, age, gender, body composition (muscle mass)	Body size, genetics, occupation, leisure choices
Conscious Control	Very little direct conscious control	A high degree of conscious control (e.g., opting to stand)
Impact on Weight Management	Sets the baseline metabolic 'floor'; maintaining muscle is key	The most flexible lever to increase calorie burn; promotes an active lifestyle

Conclusion

The most significant and consistent contributor to daily energy expenditure is the Basal Metabolic Rate, which powers the body's essential functions at rest. While BMR is influenced by factors like body size, age, and muscle mass, lifestyle choices are also crucial. Increasing physical activity, particularly through Non-Exercise Activity Thermogenesis (NEAT), and consuming foods like protein that require more energy to process (TEF), are effective ways to boost overall calorie burn. Understanding these three components—BMR, NEAT, and TEF—is vital for sustainable health and weight management.

Authoritative Source on Metabolism

For more in-depth information on the components of human energy expenditure, explore the comprehensive review on this topic published by the National Institutes of Health (NIH).

Frequently Asked Questions

The Basal Metabolic Rate (BMR) is the largest component of total daily energy expenditure, accounting for 60-70% of the calories burned per day. It covers the energy needed for your body's basic functions at rest.

Muscle tissue is more metabolically active than fat tissue. As a result, individuals with a higher percentage of lean muscle mass have a higher basal metabolic rate, meaning they burn more calories at rest.

Basal Metabolic Rate (BMR) is the energy expenditure measured under the strictest, most controlled conditions (e.g., after a 12-hour fast and 8 hours of sleep). Resting Metabolic Rate (RMR) is measured under slightly less restrictive conditions and is typically around 10% higher than BMR.

Yes, this is known as the Thermic Effect of Food (TEF). Your body uses energy to digest, absorb, and process nutrients. Protein has the highest thermic effect, meaning you burn more calories digesting it than fats or carbohydrates.

NEAT stands for Non-Exercise Activity Thermogenesis, which is the energy expended for all activities outside of planned exercise. You can increase your NEAT by taking the stairs, walking more frequently, fidgeting, and choosing to stand instead of sit.

While exercise can burn a significant number of calories in a single session, the overall contribution of the Basal Metabolic Rate (BMR) over a 24-hour period is much larger for most people. Physical activity is the most variable factor, but BMR is the largest consistent contributor.

Yes, your basal metabolic rate tends to decrease with age. This is mainly due to a gradual loss of lean muscle mass, though hormonal and neurological changes also play a role.