This guide explains what basal metabolism is, how it is calculated according to scientific evidence, and how to apply it to estimate daily energy needs. It can be useful for both people who want to lose fat and those who are looking to increase muscle mass in a healthy way.
To obtain a personalized estimate of basal metabolism, you can use this calculation tool: https://www.quotavita.com/pages/calculadora-metabolisme-basal
What is basal metabolism?
Basal metabolic rate (BMR) , also known as resting energy expenditure (REE) , is the minimum amount of energy the body needs to maintain vital functions while at physical and mental rest. It includes essential processes such as:
- Heartbeat and blood circulation
- Brain activity and nervous system function
- Breathing
- Tissue maintenance, repair and regeneration
- Hormonal production and regulation
In most people, basal metabolism represents approximately 60% to 75% of the total calories expended throughout the day.
What factors influence basal metabolism?
Metabolic expenditure can vary significantly between people. Some of the factors that influence it are:
The more muscle mass you have, the more energy your body consumes at rest, since muscle tissue is metabolically active.
Metabolism tends to decrease with age and, on average, is higher in men due to a higher percentage of lean mass.
Biological and lifestyle factors can speed up or slow down basal metabolism.
Components of Total Energy Expenditure (TDEE)
Total Daily Energy Expenditure (TDEE) is the sum of all the calories your body burns in a day. It includes four main components:
| Component | Approximate percentage | Description |
|---|---|---|
| Basal metabolism (MB/REE) | 60–75% | Energy needed to maintain the body's vital functions |
| Physical activity (NEAT + exercise) | 15–30% | Daily movement, spontaneous activity and planned exercise |
| Thermogenesis of food (TEF) | 8–10% | Energy used to digest and metabolize food |
| Additional factors | Variable | Such as stress, fever, pregnancy or breastfeeding |
How to calculate basal metabolism
Several scientific formulas allow us to estimate basal metabolic rate. One of the most widely used in adult nutrition is the Mifflin–St Jeor formula , especially in healthy people who want to control their body weight. However, it is important to understand its real scope.
The Mifflin–St Jeor formula is useful for estimating basal metabolic rate in adults of stable weight, and is often used in the context of general nutrition, weight loss, and fitness. However, according to a study published by Weijs et al. in 2008 in the scientific journal Clinical Nutrition , this formula was not the most accurate when compared with actual measurements of resting energy expenditure in adult patients.
Calculation with the Mifflin–St Jeor formula
Men: MB = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
Women: MB = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
To obtain an automated estimate with this formula, you can use this tool: QuotaVita Basal Metabolism Calculator
What is the most accurate formula according to scientific evidence?
It is important to differentiate between the most commonly used formulas and the most accurate ones according to scientific research. The study by Weijs et al. (2008), which analyzed 18 formulas in 48 outpatients and 45 hospitalized patients, concluded that the FAO/WHO/UNU (1985) formula that includes weight and height was the one that showed the lowest prediction error compared to indirect calorimetry, both in:
- Outpatients
- Hospitalized patients
- Underweight people
The study also highlights that the revised Harris–Benedict formula (1984) was a good alternative, with similar results in accuracy. In contrast, the Mifflin–St Jeor formula showed good results especially in hospitalized and underweight patients, but was not the most accurate overall .
How to apply basal metabolism to adjust energy intake
Once the basal metabolism and total energy expenditure (TDEE) are known, it is possible to adapt the energy intake to the goal:
- Weight loss: approximately 10–20% reduction in daily calories to promote progressive fat loss.
- Muscle mass gain: approximately 5–15% increase in daily calories to promote muscle development.
- Body weight maintenance: ingesting a level of calories similar to TDEE keeps weight stable.
Common mistakes that can affect metabolism and progress
Some practices can make it difficult to achieve the desired results:
- Cutting calories too much, which can slow down your metabolism
- Consuming little protein, essential to preserve muscle mass
- Not adjusting intake when weight or activity level changes
- Focus only on calories and not on nutritional quality
- Leading a sedentary lifestyle with little daily activity
Based on scientific evidence
The information on this page has been compiled taking into account data from the study by Weijs et al. (2008) published in the journal Clinical Nutrition , which comparatively analyzed the accuracy of 18 formulas for estimating resting energy expenditure in adults. This study concluded that the FAO/WHO/UNU (1985) formula with weight and height was the most accurate in outpatients, hospitalized patients, and underweight patients. This provides a useful framework for understanding the actual role of each formula, even for people who want to manage their weight outside of a clinical setting.
Scientific source: Validation of predictive equations for resting energy expenditure in adult outpatients and inpatients (Weijs et al., 2008).