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Measurement of resting energy expenditure

Resting energy expenditure (REE) is the amount of energy your body uses at rest to carry out essential physiological functions. It reflects the body's calories requirements at rest and is influenced by factors such as age, sex, body composition and hormonal status.

REE is important for understanding overall energy requirements and for designing personalised nutrition and fitness plans.

It can be estimated by formulas or, more precisely, measured directly by methods like this: VO2max or the study of oxygen consumption at rest.

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FAQ Measuring resting energy expenditure

What is resting energy expenditure?

Resting Energy Expenditure (REE) represents the body's energy expenditure when not engaged in physical activity. It is sometimes referred to as the Basal Metabolic Rate (BMR) when measured under very strict conditions (for example, after a full night's sleep, on an empty stomach, and in a thermo-neutral environment).

What are the components of resting energy expenditure?

REE includes the energy needed for:

Respiration: The energy needed to breathe.

Circulation: Maintaining blood flow and heart function.

Cellular metabolism: The energy needed for cellular processes and maintenance.

Thermogenesis: The energy needed to maintain body temperature.

What factors can affect resting energy expenditure?

Age: REE generally decreases with age, partly due to loss of muscle mass.

Gender: In general, men have a higher REE than women, mainly due to greater muscle mass.

Body composition: Muscle tissue consumes more energy than fat tissue, so individuals with more muscle mass tend to have a higher REE.

Genetics: Genetic factors can influence metabolic rate and therefore affect REE.

Hormones: Hormonal changes, particularly those involving thyroid hormones, can influence REE. For example, hypothyroidism (reduced thyroid function) can decrease REE.

How is resting energy expenditure measured?

Indirect calorimetry measures the body's consumption of oxygen (O₂) and production of carbon dioxide (CO₂). The amount of these gases exchanged is used to estimate energy expenditure.

How do I prepare for the test?

The individual should be in a state of complete rest, usually after an 8- to 12-hour fast, and in a thermoneutral environment.

The individual breathes through a mask or mouthpiece connected to a gas analyzer. Measurements are taken over a specific period, often 15 to 20 minutes.

The oxygen consumption and carbon dioxide production values are used to calculate energy expenditure according to specific formulas.

What are the clinical applications of these results?

Measuring an individual's resting energy expenditure (REE) is essential for understanding their basal metabolic rate and assessing energy needs.

Nutritional assessment: Understanding REE helps plan appropriate caloric intake for weight management, whether for weight loss, gain, or maintenance.

Medical conditions: In patients with certain medical conditions, such as thyroid disorders or serious illnesses, REE measurements can help tailor nutritional support.

Athletic training: Athletes can use REE data to optimize their nutrition and training regimens.