What Is Basal Metabolic Rate(BMR)?

Even when resting, your body burns calories by performing basic functions to sustain life, such as:

  • breathing
  • circulation
  • nutrient processing
  • cell production

Basal Metabolic Rate (BMR) is the number of calories your body needs to accomplish its most basic (basal) life-sustaining functions.

Basal Metabolic Rate( BMR ) vs. Resting Metabolic Rate( RMR )

Basal metabolic rate (BMR) is often used interchangeably with resting metabolic rate (RMR). While BMR is a minimum number of calories required for basic functions at rest, RMR — also called resting energy expenditure (REE) — is the number of calories that your body burns while it’s at rest.

Although BMR and RMR slightly differ from each other, your RMR should be an accurate estimate of your BMR.

How to estimate your BMR 

To measure BMR scientificly accurately the following two methods are used:-

  1. Direct Calorimetry
    1. Total energy expenditure is directly estimated by heat produced.
    2. Involves placing the individual inside the isolated chamber and directly measuring the temperature raised.
    3. This is an accurate way of measurement.
  2. Indirect Calorimetry
    1. Entails measuring exchange of gases during respiration i.e., carbon dioxide given off and oxygen inhaled by lungs also called as respiratory quotient.

RQ = CO2 eliminated / O2 consumed

One popular way to estimate BMR is through the Harris-Benedict formula, which takes into account weight, height, age, and gender.

Women:BMR = 655 + (9.6 × weight in kg) + (1.8 × height in cm) – (4.7 × age in years)

Men:BMR = 66 + (13.7 × weight in kg) + (5 × height in cm) – (6.8 × age in years)

Why you might want to know your BMR 

BMR is used to help you gain, lose, or maintain your weight. By knowing how many calories you burn, you can know how many to consume. To put it simply:

  • Is your goal to maintain your weight? Consume the same number of calories that you burn.
  • Is your goal to gain weight? Consume more calories than you burn.
  • Is your goal to lose weight? Consume fewer calories than you burn.

How many calories you need everyday

If you’ve estimated your BMR using the Harris-Benedict formula, your next step is to include the number of calories you burn during daily activities based on your lifestyle:

  • If you are sedentary (little or no exercise)
    Calories Per Day = BMR x 1.2
  • If you are lightly active (light exercise or sports 1-3 days/week)
    Calories Per Day = BMR x 1.375
  • If you are moderately active (moderate exercise 3-5 days/week)
    Calories Per Day = BMR x 1.55
  • If you are very active (hard exercise 6-7 days/week)
    Calories Per Day = BMR x 1.725
  • If you are super active (very hard exercise and a physical job)
    Calories Per Day = BMR x 1.9

The Output of the formula gives you an estimate of how many calories you need on a daily basis to maintain your weight.

Of course, this is still an ESTIMATE. According to a 2007 study, the formula would be more accurate if it included body composition, weight history, and other factors that have been shown to affect BMR.

How you can change your BMR 

Your BMR is determined by a number of factors, including:

  • sex ( no the cool kind )
  • weight
  • height
  • age
  • ethnicity
  • weight history
  • body composition
  • genetic factors

Of these factors, you can take steps to change your weight and body composition. So if you want to change your BMR, your first steps should be to lose weight and increase muscle.

2010 reviewTrusted Source indicated that resistance training can improve lean body mass composition and maintain fat mass reduction, increasing BMR.

Takeaway 

Understanding your BMR, your typical activity level, and the amount of calories you need daily to maintain your weight are important ways for you to actively participate in your physical health.

Whether you need to gain weight, maintain your current weight, or lose weight, calculating your BMR is a good place to start.