what is resting energy

3 min read 10-03-2025

Resting energy expenditure (REE), also known as basal metabolic rate (BMR), is the number of calories your body burns at rest to maintain basic bodily functions. It's the energy your body needs just to keep you alive – breathing, circulating blood, regulating temperature, and performing other essential processes. Understanding your REE is crucial for weight management, athletic performance, and overall health.

What Factors Influence REE?

Several factors influence your REE, making it unique to each individual. These include:

Age: REE tends to decrease with age as metabolism slows down.
Sex: Men generally have a higher REE than women due to higher muscle mass and testosterone levels.
Body Composition: More muscle mass leads to a higher REE, as muscle tissue burns more calories at rest than fat tissue.
Genetics: Your genes play a significant role in determining your metabolic rate.
Body Size and Weight: Larger individuals tend to have a higher REE because their bodies require more energy to function.
Thyroid Hormones: The thyroid gland produces hormones that regulate metabolism. Hypothyroidism (underactive thyroid) can significantly lower REE, while hyperthyroidism (overactive thyroid) can increase it.
Physical Activity: While REE measures energy expenditure at rest, regular exercise can boost your metabolism over time, impacting your overall calorie burn. This indirect effect is not directly part of your REE but significantly contributes to your total daily energy expenditure (TDEE).
Climate: Your body works harder to regulate temperature in extreme hot or cold conditions, potentially slightly increasing your REE.

How is REE Measured?

REE can be measured through several methods, each with its own level of accuracy and invasiveness:

Indirect Calorimetry: This is the gold standard method. It measures oxygen consumption and carbon dioxide production to precisely calculate REE. It’s typically done in a specialized metabolic chamber or using a portable device.
Predictive Equations: These formulas estimate REE based on factors like age, sex, weight, and height. While convenient, they are less accurate than indirect calorimetry. Examples include the Harris-Benedict equation and Mifflin-St Jeor equation. These equations provide a reasonable approximation but may not be perfectly precise for every individual.
Body Composition Analysis: Measuring body fat percentage and lean body mass can provide an indirect estimate of REE. Techniques include DEXA scans, bioelectrical impedance analysis (BIA), and underwater weighing.

Understanding REE and Weight Management

Your REE is a foundational component of your total daily energy expenditure (TDEE). TDEE includes REE plus energy expended through physical activity and the thermic effect of food (TEF). To lose weight, you need to create a calorie deficit – burning more calories than you consume. Understanding your REE helps determine a realistic calorie intake for weight loss. If you drastically reduce calories below your REE, your body may go into starvation mode, slowing down your metabolism and making weight loss more challenging.

REE and Athletic Performance

For athletes, knowing their REE is essential for optimizing training and nutrition. It helps determine the appropriate caloric intake to support training demands and prevent overtraining or underfueling. Athletes often have higher REE due to increased muscle mass and higher activity levels. Proper fueling based on a personalized understanding of REE is crucial for optimal performance and recovery.

When to Consult a Professional

If you have concerns about your metabolism, weight management, or athletic performance, consulting a registered dietitian or healthcare professional is crucial. They can help you accurately determine your REE, develop a personalized nutrition plan, and provide guidance tailored to your individual needs and health status. They can also help rule out underlying medical conditions that may affect your metabolism.

Conclusion

Resting energy expenditure (REE) is a critical measure of your body's baseline calorie burn. While various methods exist to estimate or measure REE, understanding its influence on weight management and athletic performance is essential for overall health and well-being. Consider consulting a professional to get a personalized assessment and develop a tailored plan. Remember, a healthy lifestyle that incorporates balanced nutrition and regular physical activity is key to maintaining a healthy REE and overall well-being.