What is the difference between BMR and REE?

November 20, 2025 •

3 min read

Though often used interchangeably, the Basal Metabolic Rate (BMR) and Resting Energy Expenditure (REE) are distinct measurements, differing primarily in the strictness of their testing conditions. While both quantify the calories your body burns at rest, understanding the precise difference between BMR and REE is key to accurately assessing your metabolic health.

Quick Summary

This article outlines the specific differences between BMR and REE, focusing on the rigorous testing protocols for BMR versus the more practical, less stringent conditions for REE, and explains why REE is the more common measurement in real-world scenarios.

Key Points

Measurement Conditions: BMR is measured under strict, clinical conditions (fully rested, fasted state), while REE uses less stringent, more practical conditions.
Typical Value: REE is typically slightly higher than BMR (often by less than 10%) because it accounts for minor energy use from recent activity or digestion.
Practical Application: REE is the more common and practical measurement for general health and fitness applications, whereas BMR is a more precise, but less practical, research metric.
Primary Influencers: Both BMR and REE are primarily influenced by age, sex, and body composition, especially the amount of lean muscle mass.
Predictive Estimates: Most online calculators provide an estimate of REE using formulas like the Mifflin-St Jeor equation, which is accurate enough for most people.
Clinical Diagnosis: Significant deviations between measured and predicted REE can indicate an underlying metabolic issue, such as a thyroid disorder.

BMR vs. REE: Understanding Your Body's Energy Burn

Your body continuously expends energy, even while you are at rest. This fundamental process is known as your metabolic rate. For those looking to manage their weight, optimize their nutrition, or understand their body's basic functions, the terms Basal Metabolic Rate (BMR) and Resting Energy Expenditure (REE) are essential. While both quantify your resting calorie burn, they are not identical. The primary distinction lies in the strictness of the measurement conditions, leading to subtle but important differences in their values.

The Strict Scientific Standard: Basal Metabolic Rate (BMR)

BMR represents the minimum energy your body needs for vital functions like breathing and circulation. It requires highly controlled conditions rarely found outside research settings, including being fully rested and fasted for at least 12 hours in a thermoneutral environment. This provides a precise baseline.

The Practical Clinical Metric: Resting Energy Expenditure (REE)

REE, also called Resting Metabolic Rate (RMR), is a more common, practical measurement taken under less strict conditions. It measures energy burn at rest, usually 2 to 4 hours after eating. REE is typically slightly higher than BMR (often within 10%) because it may include minor energy from digestion. The terms are often used interchangeably due to their close values.

Key Differences and Measurement Methods

The main difference between BMR and REE is the measurement methodology. Both can be measured using indirect calorimetry, which assesses oxygen use and carbon dioxide production, but the specific conditions determine which metric is obtained.

Here is a comparison of the two measurements:


Feature	Basal Metabolic Rate (BMR)	Resting Energy Expenditure (REE)
Measurement Condition	Extremely strict and controlled.	Less stringent and more practical.
Fasting State	Required, typically 12 hours minimum.	Not as strict, usually 2-4 hours after a meal.
Physical State	Completely motionless, supine, and rested.	Rested and calm, often sitting, not necessarily motionless.
Mental State	Free of stress and mental activity.	Minimal mental activity required.
Location	Specialized research or clinical setting.	Easily performed in a standard outpatient clinic.
Typical Value	Slightly lower, as it excludes digestion.	Slightly higher due to less strict conditions.
Practical Use	Primarily for research and specific clinical diagnoses.	Common for estimating daily energy needs and nutrition planning.

Factors Influencing Your Metabolic Rate

Both BMR and REE are affected by similar factors such as body composition, age, sex, genetics, and hormonal factors. More lean mass increases metabolic rate, which slows with age. Men often have higher rates than women, and genetic and hormonal factors also play a role.

The Importance for Weight and Health

For most people, estimating REE (or RMR) with a calculator is sufficient for managing caloric needs. REE is the largest part of your Total Daily Energy Expenditure (TDEE), which includes the thermic effect of food and activity. Understanding your REE helps calculate TDEE and plan for weight goals.

Conclusion

The core difference between BMR and REE lies in the measurement conditions. BMR is a highly controlled, research-level measure of minimal energy needs, while REE is a more practical clinical measure taken under less strict conditions, resulting in a slightly higher value. REE is more relevant for everyday health and nutrition planning. Despite their differences, their close values mean they are often used interchangeably for general health assessments and dietary planning. For more detailed information, please refer to {Link: Fiveable me https://fiveable.me/nutrition-assessment/unit-7/basal-metabolic-rate-bmr-resting-energy-expenditure-ree/study-guide/MozmGekLeVGx9jcD}.

Frequently Asked Questions

BMR stands for Basal Metabolic Rate, which is the minimum number of calories your body needs to perform essential, life-sustaining functions while at complete rest.

REE stands for Resting Energy Expenditure, which is the number of calories your body burns while at rest under less strict, more practical conditions than BMR.

REE is typically slightly higher than BMR (often by less than 10%), as the less stringent measurement conditions for REE can include residual energy from recent activity or digestion.

BMR is measured using indirect calorimetry in a specialized clinical setting, requiring the subject to be in a fully rested, fasted, and thermoneutral state.

REE is measured via indirect calorimetry in a clinical or outpatient setting, with the subject calmly resting, typically 2-4 hours after a meal.

REE is more commonly used because its less rigorous testing requirements make it more practical and easier to obtain for clinical purposes and general assessments.

No, the difference between BMR and REE is generally small, often less than 10%, which is why the terms are frequently used interchangeably in many contexts.

Yes, you can estimate your BMR or REE using predictive equations like the Harris-Benedict or Mifflin-St Jeor formulas, though these are less precise than a lab measurement.

Both are affected by factors such as age, sex, body composition (especially lean muscle mass), genetics, and hormonal status.

Both serve as a baseline for determining your total daily energy expenditure, helping to create personalized nutrition plans for weight management.

Yes, certain medical conditions, such as thyroid disorders (hyperthyroidism or hypothyroidism), can significantly impact your metabolic rate.