Basal Metabolic Rate (BMR)

What is basal metabolic rate?

Basal Metabolic Rate (BMR) is primarily the amount of energy (in calories) that your body requires to ensure that the basic or primary functions of the body are maintained while you are in a state of rest. These basic or primary functions include:

• Digestion
• Breathing
• Cell growth and repair
• Blood circulation
• Body temperature regulation
• Functioning of the nervous system

Basal Metabolic Rate is therefore the basic minimum amount of calories required to ensure that the above life-sustaining functions are carried out while our bodies are at rest, i.e., no additional activity is being carried out by the body.

What are some factors that affect or influence Basal Metabolic Rate?

A number of factors influence basal metabolic rate (BMR) in our bodies, including:

• Lifestyle: An active lifestyle with regular exercising, especially strength trainings that help build muscle mass, raises basal metabolic rate (BMR) in the body while, on the other hand, a sedentary lifestyle, with no exercise or activity, leads to a lower BMR level.
• Age factor: Generally, younger age groups tend to have higher BMRs on account of increased muscle mass while older people, due to declining muscle mass, experience a decline in BMR.
• Gender: Men generally tend to have higher BMRs on account of more muscle mass and less body fat whereas women, on the other hand, have lower BMRs due to higher levels of body fat.
• Body composition and size: Individuals with higher muscle mass and lower body fats as well as those who are larger in size (taller and heavier) have higher BMRs as their bodies require more energy to function.
• Genetic: Metabolism may also depend on one’s genes. Some individuals may have a higher BMR due to their genetic makeup.
• Fasting / diet: Fasting or crash diets may lower BMR as the body slows down its rate of metabolism whereas a protein rich diet can increase BMR.
• Temperature: High or low body temperatures may lead to high BMR as the body burns more calories.
• Sleep: Lack of sleep, leading to hormonal imbalances in the body, can lead to a decrease in BMR.

How do you estimate your Basal Metabolic Rate (BMR)?

While there are number of methods to estimate BMR, the most common and widely recognized are the Harris-Benedict and Mifflin-St Jeor equations, which consider age, gender, height and weight to estimate an individual’s caloric requirements when the body is at rest:

• Mifflin-St Jeor Equation

  • BMR for Men:
    10×weight (kg)+6.25×height (cm)−5×age (years)+5
  • BMR for Women:
    10×weight (kg)+6.25×height (cm)−5×age (years)−161

• Harris-Benedict Equation

  • BMR for Men:
    88.362+(13.397×weight in kg)+(4.799×height in cm)−(5.677×age in years)
  • BMR for Women:
    447.593+(9.247×weight in kg)+(3.098×height in cm)−(4.330×age in years)

Why is it important to know your Basal Metabolic Rate (BMR)?

Knowing your basal metabolic rate is important to understand your daily caloric needs, weight management and also for your fitness goals:

• Daily Caloric needs: Your BMR identifies the basic minimum amount of calories required to keep your body functioning while at rest. Knowing your BMR, therefore, provides a clear picture of the minimum number of calories that your body requires. You may then choose the additional amount of calories depending on your activity schedule.
• Weight Management: Knowing your BMR can help you:
  • Maintain your weight: Since you know the minimum daily calories that your body requires (while at rest), all you need to do is consume the same level of calories to maintain your weight.
  • Weight loss: Consuming lesser amount of calories than your daily caloric requirement (as per your BMR) can help you lose weight.
  • Weight gain: Knowing your BMR can help you estimate the additional calories that your body may require for gaining weight or muscles.
• Health goals: Being aware of your body’s metabolism rate helps you make adjustments to your lifestyle, by way of either increasing your physical activity or improving your diets in line with your health goals.
• Optimizing fitness: Knowing your BMR helps optimize nutrition intake and maintain performance levels during your fitness routines.

Can you change your BMR?

While an individual’s basal metabolic rate (BMR) is largely dependent on factors such as age, gender, body composition and genes, there are ways by which BMR can be changed, atleast to some extent:

• Increasing Muscle Mass: The very fact that muscle tissue burns more calories than fat, even when the body is at rest, implies that the more muscle mass one has, the higher will be the BMR. Therefore, increasing muscle mass can help you increase your basal metabolic rate.
• Increasing calorie intake: Calorie deficiency in our bodies can slow BMR as the body, in such situations, starts conserving energy. Higher calorie intake can help increase BMR.
• High-intensity workouts: High-intensity workouts can increase your BMR as even after the workout, the body continues to burn calories during the recovery phase.
• High-Protein diet: Digesting proteins require more energy than fats and as a result a protein-rich diet may also help increase the basal metabolic rate in our bodies.
• Sleep: Lack of sleep or irregular sleeping habits can result in imbalance of hormones in the body, leading to lack of appetite and energy requirements in the body, hence slowing down the body’s BMR.
• Hydration: Staying hydrated can help maintain the body’s metabolism rate, hence increasing BMR. Dehydration, on the other hand, adversely impacts the body’s ability to burn down calories.

FAQs

What is the difference between Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE)?

While Basal Metabolic Rate (BMR) is the amount of calories that your body requires to function when at rest, Total Daily Energy Expenditure (TDEE), is the total energy that your body requires in a day. In other words, TDEE is BMR plus calories burned through physical activity as well as digestion.

Can one’s Basel Metabolic Rate (BMR) change with time?

Yes, Basal Metabolic Rate (BMR) is largely depending on biological factors such as age, muscle mass, weight, hormonal changes, etc., and can change overtime as and when a person ages or looses or gains weight, etc.

Can exercising increase Basel Metabolic Rate (BMR)?

Yes, exercise, high-intensity workout or strength training in particular, leading to increase in muscle mass can increase BMR as muscles burn higher calories than fat.

Does dieting or fasting affect Basel Metabolic Rate (BMR)?

Yes, fasting or dieting may lower your BMR as your body slows down the metabolism rate during dieting to conserve energy.

What is the difference between BMR and Resting Metabolic Rate (RMR)?

While both BMR and RMR primarily measure the amount of calories required by our bodies for functioning while in a state of rest, BMR is measured under more stricter conditions than RMR and hence there may be a difference in the readings of the two measures.

What happens if you eat below your BMR?

If you consistently eat below your BMR, you are likely to enter a state of ‘starvation’ wherein your body will slow down your metabolism rate to conserve energy.