Basal Metabolic Rate (BMR)

What is Basal Metabolic Rate (BMR)?

Also known as Basal Metabolism or Basal Energy Expenditure, it is an index that allows estimating the minimum amount of calories that a person's body consumes to perform basic functions such as breathing, pumping blood, synthesizing hormones, regulating body temperature, among other things. This minimum energy expenditure required by the body varies according to sex, age, and the physical activity the person performs weekly.

How is Basal Metabolic Rate calculated? Harris-Benedict formula

Using the latest Harris-Benedict Equations (1990) as a base, basal metabolism is estimated using the following calculation formulas:

Harris-Benedict Formula for Men:

Harris-Benedict Formula for Women:

Finally, the calculated BMR is adjusted by multiplying it by the physical activity factor that appears in the table above. You should consider that this formula contemplates average relationships of muscle mass and fat mass, so for people with a lot of muscle or morbid obesity, the estimation may be imprecise.

BMR Table According to Physical Activity

Based on how often you exercise, determine the range that corresponds to you to calculate your Basal Metabolic Rate more accurately.

Who were Harris and Benedict?

Harris and Benedict were two men who made significant contributions in the field of nutrition and medicine, particularly in the development of equations to estimate people's daily caloric needs. Their respective works have been fundamental in calculating energy requirements and have served as the basis for many formulas used today to calculate basal metabolic rate (BMR) or daily caloric requirement.

1. James Arthur Harris: He was an American physiologist who worked at the Carnegie Institution of Washington. In 1919, he published a study proposing an equation to calculate basal metabolism based on weight, height, and age, thus establishing the basis for estimating resting energy expenditure.
2. Francis Gano Benedict: He was an American chemist and nutritionist who worked at the same institution as Harris. In 1919, Benedict and his collaborator, Talbot, published an article presenting an equation similar to Harris's but with gender-based adjustments. This refined equation was widely adopted and became a standard tool for estimating basal metabolic rate.

The Harris-Benedict equations have been modified and adjusted over time to improve their accuracy, but the foundation of their work has been essential in nutrition and medicine, providing a fundamental way to estimate people's basic caloric needs. These equations have been and continue to be useful in fields such as clinical nutrition, weight loss, fitness, and diet planning.

How to Use Basal Metabolic Rate to Lose Weight?

Basal Metabolic Rate provides us with an estimate of the minimum daily calorie expenditure that our body needs to function. If we consume fewer calories than the estimated BMR, we would achieve a caloric deficit, which would lead to weight loss. The larger this deficit, the faster the weight loss.

BMR is useful when we want to estimate planned weight loss over time. If we consider that 1 kg of fat is equivalent to about 7,700 calories, using Basal Metabolic Rate, we can estimate the daily caloric deficit our body needs to lose X kilograms in a defined time frame.

For example, let's assume that our BMR is 2,000 daily calories, and our goal is to lose 1 kg of body fat (7,700 calories) in 1 month. That means we need a daily caloric deficit of 257 calories for 30 days. If we subtract this deficit of 257 from the 2,000 basal calories, it can be deduced that we must consume less than 1,743 calories per day to achieve the goal.

What factors can affect basal metabolic rate?

Basal metabolic rate (BMR) is the amount of calories the body needs to perform its basic functions, such as breathing, blood circulation, and temperature regulation. BMR can be influenced by a variety of factors, including:

1. Age: BMR decreases with age as the body loses muscle mass as we get older.
2. Gender: BMR is typically higher in men than in women due to greater muscle mass and hormonal differences.
3. Weight and height: BMR is usually higher in larger individuals with more muscle mass because these tissues require more energy to function.
4. Body composition: BMR can be affected by the amount of fat and muscle tissue in the body. Muscle mass requires more energy to function than fat tissue, so individuals with more muscle have a higher BMR.
5. Hormones: Hormones like thyroid hormones can affect BMR as they control the body's metabolism.
6. Genetics: BMR can also be influenced by genetic factors.
7. Lifestyle: Lifestyle can also affect BMR, for example, physical activity and stress.

How can I increase my basal metabolic rate?

There are some ways to increase the basal metabolic rate (BMR) to help burn more calories throughout the day:

1. Physical exercise: Physical exercise can increase BMR as the body needs more energy for physical activity. Resistance exercises, like weightlifting, are especially effective in increasing BMR because the body requires more energy to build and maintain muscle.
2. Increase muscle mass: As mentioned earlier, muscle mass requires more energy to function than fat tissue, so increasing muscle mass can help raise BMR. This can be achieved through resistance exercises like weightlifting.
3. Consume proteins: Proteins are essential for building and maintaining muscle mass and can also help increase BMR. It is recommended to consume at least 0.8 grams of protein per kilogram of body weight per day.
4. Consume an adequate amount of food: Ensuring you consume enough food is important to maintain BMR because the body needs fuel to function. If you don't consume enough food, your body may go into "energy-saving mode" and decrease BMR.
5. Reduce stress: Chronic stress can affect hormone production and lower BMR. Working on stress-reduction techniques, like meditation and deep breathing, can help increase BMR.

What is the relationship between basal metabolic rate and aging?

Basal metabolic rate (BMR) decreases with age, decreasing by approximately 2-3% per decade after the age of 40, which can contribute to weight loss and increased body fat in aging. Metabolism becomes less efficient in burning calories with age. However, it is possible to maintain or increase BMR through a healthy lifestyle and exercise, especially resistance training, along with a protein-rich diet and adequate food intake.