What is Resting Energy Expenditure (REE)?
Resting Energy Expenditure (REE) represents the total number of calories your body burns at rest to maintain basic physiological functions like breathing, circulating blood, and cellular repair. While often used interchangeably with Basal Metabolic Rate (BMR), REE is measured under less restrictive conditions and is typically around 10% higher than BMR because it includes minimal activity. Understanding your REE is crucial for effective weight management as it sets the baseline for your total daily calorie needs.
Methods to Calculate REE
There are several equations used to estimate REE. Two commonly used methods are the Mifflin-St Jeor and Harris-Benedict equations.
The Mifflin-St Jeor Equation
The Mifflin-St Jeor equation is considered a more modern and generally accurate method for estimating REE for most individuals. It incorporates weight, height, age, and gender.
For Men: $REE = (10 \times \text{weight in kg}) + (6.25 \times \text{height in cm}) - (5 \times \text{age in years}) + 5$
For Women: $REE = (10 \times \text{weight in kg}) + (6.25 \times \text{height in cm}) - (5 \times \text{age in years}) - 161$
The Harris-Benedict Equation
The Harris-Benedict equation is a classic formula, first developed in the early 20th century. While less accurate for modern lifestyles than Mifflin-St Jeor, it is still referenced.
For Men: $REE = (88.4 + 13.4 \times \text{weight in kg}) + (4.8 \times \text{height in cm}) - (5.68 \times \text{age})$
For Women: $REE = (447.6 + 9.25 \times \text{weight in kg}) + (3.10 \times \text{height in cm}) - (4.33 \times \text{age})$
Comparing Calculation Methods
| Feature | Mifflin-St Jeor Equation | Harris-Benedict Equation |
|---|---|---|
| Accuracy | Generally considered more accurate | May overestimate in modern populations |
| Primary Variables | Weight, Height, Age, Gender | Weight, Height, Age, Gender |
From REE to Total Daily Energy Expenditure (TDEE)
Your REE is a baseline. To find your total daily calorie needs (TDEE), you multiply your REE by an activity factor based on your physical activity level.
Activity Level Multipliers:
- Sedentary: REE x 1.2
- Lightly Active: REE x 1.375
- Moderately Active: REE x 1.55
- Very Active: REE x 1.725
- Extra Active: REE x 1.9
TDEE provides an estimate of the calories needed to maintain your current weight.
Factors Influencing REE
Beyond the formula variables, several factors impact your REE:
- Body Composition: More lean muscle mass increases REE because muscle is more metabolically active than fat.
- Age: REE tends to decrease with age.
- Genetics: Individual metabolic rates can vary due to genetics.
- Diet: Severe calorie restriction can slow metabolism, while adequate protein intake can slightly increase it.
- Hormones: Conditions like thyroid disorders and stress levels affect metabolism.
- Temperature: Extreme temperatures require more energy for temperature regulation.
How to Potentially Boost Your REE
While genetics play a part, lifestyle choices can influence your REE:
- Strength Training: Building muscle is effective in increasing REE.
- Protein Intake: Protein has a higher thermic effect, burning more calories during digestion.
- Hydration: Staying hydrated helps metabolic processes function efficiently.
- Sleep: Adequate sleep supports hormone balance crucial for metabolism.
- Stress Management: High stress can negatively impact metabolism.
Conclusion
Calculating your resting energy expenditure provides valuable insight into your body's basic calorie needs. Using equations like Mifflin-St Jeor or Harris-Benedict offers a good estimate, which can then be adjusted for activity level to determine Total Daily Energy Expenditure. Understanding the various factors that influence REE, such as body composition, age, and lifestyle, allows for a more personalized approach to managing health, weight, and fitness goals. Focusing on building muscle, consuming enough protein, and prioritizing rest are practical strategies to support a healthy metabolism.
For further reading on the science of energy expenditure, explore studies on the National Institutes of Health website(https://www.ncbi.nlm.nih.gov/books/NBK591031/).
