What are the three ways in which calories are spent in your body?

December 13, 2025 •

3 min read

Did you know that up to 75% of your daily calorie burn is used just to keep your body functioning at rest? Your body constantly spends calories through three primary processes: the Basal Metabolic Rate (BMR), the Thermic Effect of Food (TEF), and physical activity. Understanding how these systems work is key to managing your energy balance and weight.

Quick Summary

The total calories your body burns each day, known as Total Daily Energy Expenditure (TDEE), is composed of three main components: your Basal Metabolic Rate (BMR), the Thermic Effect of Food (TEF), and Physical Activity. BMR is the energy for basic functions at rest, TEF is the energy used for digestion, and physical activity covers all movement.

Key Points

BMR Powers Basic Functions: The Basal Metabolic Rate accounts for the largest share of daily calories, used for vital organ functions and cellular processes at rest.
TEF Aids Digestion: The Thermic Effect of Food uses approximately 10% of total calories to digest and metabolize the food you eat, with protein requiring more energy to process.
Activity Boosts Calorie Burn: Physical activity is the most variable part of calorie expenditure, covering everything from structured exercise to daily movement (NEAT).
Muscle Mass Affects BMR: Building lean muscle mass through resistance training is a key way to increase your BMR, as muscle burns more calories at rest than fat.
Lifestyle Changes Impact Balance: For weight management, focusing on controllable factors like physical activity and protein intake can effectively influence your energy balance.
Genetics Play a Role: Your BMR is also influenced by genetic predisposition, as well as age, gender, and body size.

1. Basal Metabolic Rate (BMR)

Your BMR is the largest component of your daily calorie expenditure, accounting for 60-75% of the total calories you burn. It represents the energy your body uses to perform basic life-sustaining functions while at complete rest. Think of it as the energy required to power your internal engine—keeping your heart beating, circulating blood, breathing, and maintaining body temperature.

Factors Influencing BMR

Your BMR is not static and is affected by several factors:

Body Size and Composition: Larger individuals and those with more lean muscle mass have a higher BMR because muscle tissue requires more energy to maintain than fat tissue.
Gender: Due to a generally higher proportion of muscle mass, men typically have a faster BMR than women.
Age: As you age, your metabolism naturally slows down, primarily due to a gradual loss of muscle mass.
Genetics: Your inherent genetic makeup influences your baseline metabolic rate.

2. Thermic Effect of Food (TEF)

Another way your body burns calories is through the Thermic Effect of Food, also known as diet-induced thermogenesis. This is the energy expended to digest, absorb, transport, and store the nutrients from the food you eat. TEF typically accounts for about 10% of your total daily calorie burn, though this can vary depending on the food's composition.

Macronutrients and TEF

The macronutrient composition of a meal significantly impacts how much energy is spent on digestion:

Protein: Requires the most energy to process, with a TEF of 20-30% of its total calories.
Carbohydrates: Have an intermediate TEF of 5-15%.
Fats: Require the least amount of energy to digest, with a TEF of 0-5%.

3. Physical Activity Energy Expenditure (PAEE)

The most variable component of your daily calorie expenditure is Physical Activity Energy Expenditure, which includes both structured exercise and all other movement throughout the day. For sedentary individuals, this might account for a small percentage, but for highly active people, it can account for 30% or more of their total daily energy expenditure. PAEE can be divided into two subcategories:

Exercise Energy Expenditure (EEE): The calories burned during structured, intentional workouts like running, cycling, or weightlifting.
Non-Exercise Activity Thermogenesis (NEAT): The energy used for all other daily movement, from walking to fidgeting, gardening, and even standing. Increasing NEAT can be a simple way to boost your overall calorie burn.

Comparing the Three Calorie-Burning Methods

To better understand how these three components contribute to your total daily energy expenditure, consider the following comparison:


Feature	Basal Metabolic Rate (BMR)	Thermic Effect of Food (TEF)	Physical Activity Energy Expenditure (PAEE)
Energy Source	Internal organ function, cellular repair	Digestion, absorption, nutrient storage	Skeletal muscle movement
Contribution to TDEE	60-75% (Largest component)	~10% (Smallest component)	15-30% (Most variable component)
Variability	Relatively stable, influenced by genetics, age, and body composition	Modest variations based on meal composition and size	Highly variable, dependent on daily movement and exercise intensity
Controllability	Less controllable, but can be influenced by building muscle mass	Modestly controllable by diet choices (e.g., higher protein meals)	Highly controllable through conscious activity levels and exercise

Conclusion: Your Energy Balance Equation

Your total daily energy expenditure is the sum of your BMR, TEF, and PAEE. While BMR forms the largest, most consistent portion of your daily calorie burn, your physical activity level and dietary choices offer the greatest opportunities for influence. For weight management, creating a calorie deficit by burning more than you consume is key. This can be achieved by increasing your PAEE through more movement or by strategically adjusting your diet to take advantage of the TEF. A balanced approach focusing on all three areas—supporting BMR with muscle mass, prioritizing high-protein foods for TEF, and boosting daily activity—provides a comprehensive strategy for managing your energy balance and overall health. For further reading, the National Institutes of Health offers extensive resources on energy expenditure and metabolism, which can help deepen your understanding.

Frequently Asked Questions

The three main components are the Basal Metabolic Rate (BMR), the Thermic Effect of Food (TEF), and Physical Activity Energy Expenditure (PAEE).

The Basal Metabolic Rate (BMR) is responsible for the largest portion of your daily calorie burn, typically accounting for 60-75% of your total energy expenditure.

TEF is the energy your body uses to digest, absorb, and process the nutrients from the food you eat. It generally accounts for about 10% of your daily calorie expenditure.

Physical activity includes all energy spent on movement, from formal exercise to daily, non-exercise activities like walking and fidgeting. It is the most variable component of your daily calorie burn and can be influenced the most.

Yes, a healthy way to increase your BMR is to build lean muscle mass through strength training, as muscle tissue burns more calories at rest than fat tissue.

Yes, different macronutrients have different thermic effects. Protein has the highest TEF, meaning your body uses more energy to process it compared to carbohydrates or fats.

NEAT stands for Non-Exercise Activity Thermogenesis, and it includes all the calories burned from daily movements outside of intentional exercise. Increasing NEAT through simple changes, like taking the stairs or walking more, can boost your total calorie expenditure.