Harris Benedict Calculator (BMR) | Eqution and Examples

Harris-Benedict Eqution

The Harris-Benedict equation is a mathematical formula used to estimate the daily calorie needs of individuals. This equation helps predict a person's daily energy requirements based on factors such as age, gender, weight, height, and activity level. It can be useful in determining how many calories individuals need to maintain their body weight, lose weight, or gain weight.

This calculates the basic calorie expenditure of a person at rest, taking into account their weight, height, age, and gender. One of the commonly used formulas is as follows:

For Men: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age)

For Women: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age)

The BMR is multiplied by an activity level factor to calculate the daily total calorie requirement, taking into account the individual's daily activity level. Activity levels are often categorized as sedentary (very little or no exercise), lightly active, moderately active, and very active, and different multipliers are used for each activity level.

For example, to determine the daily calorie requirement after calculating daily activity, you can use the Harris-Benedict equation as follows:

Daily Calorie Requirement = BMR x Multiplier for Activity Level

The Harris-Benedict equation can be used to estimate a person's basic energy needs, but it's important to consider factors such as an individual's body composition, genetic factors, and other specific circumstances. This is just an estimation, and seeking help from a professional dietitian or health expert may be a better approach to determine an individual's actual calorie needs.

What is BMR? (Basal Metabolic Rate)

BMR, which stands for Basic Metabolic Rate, is the amount of energy your body needs to maintain basic functions while at rest. It represents the minimum amount of calories required for your body to carry out essential physiological functions. BMR is calculated based on factors such as your age, gender, weight, and height.

Calculating BMR can be done using formulas like the Harris-Benedict equation. These formulas take into consideration basic physical factors such as gender, age, weight, and height to estimate an individual's BMR.

Your BMR forms the basis of your daily calorie needs. By taking your BMR and multiplying it by activity factors that consider your daily activities and lifestyle, you can determine your daily total calorie requirement.

Understanding your BMR is important for managing your calorie intake, whether you are looking to maintain your current weight, lose weight, or gain weight.

History of the Harris-Benedict Equation

The Harris-Benedict Equation, used for estimating daily calorie needs based on various factors, has a notable history dating back to the early 20th century. It was developed independently by two pairs of researchers, James Arthur Harris and Francis Gano Benedict.

James Arthur Harris and Francis Gano Benedict:

• In 1919, American scientists James Arthur Harris and Francis Gano Benedict published a paper titled "A Biometric Study of Human Basal Metabolism" in the Proceedings of the National Academy of Sciences.
• They conducted extensive experiments to measure oxygen consumption and calorie expenditure at rest.
• Based on their research, they derived equations to estimate Basal Metabolic Rate (BMR) for both men and women.

Original Harris-Benedict Equations:

• For Men: BMR = 66.47 + (13.75 x weight in kg) + (5.003 x height in cm) - (6.75 x age in years)
• For Women: BMR = 655.1 + (9.563 x weight in kg) + (1.850 x height in cm) - (4.676 x age in years)

The Harris-Benedict Activity Factors

The Harris-Benedict Activity Factors, also known as the Harris-Benedict Multipliers, are used to adjust a person's Basal Metabolic Rate (BMR) to estimate their total daily calorie needs based on their level of physical activity. These factors take into account the intensity of a person's daily activities and lifestyle. There are different activity factors for various activity levels, ranging from sedentary (little to no exercise) to very active (high-intensity exercise or physically demanding jobs).

Common Activity Factors:

• Sedentary (little to no exercise):
  • Activity Factor: 1.2
  • Description: If you have a desk job, do minimal physical activity, and rarely exercise, this factor is used.
• Lightly active (light exercise or sports 1-3 days a week):
  • Activity Factor: 1.375
  • Description: If you engage in light exercise, such as walking or light sports, a few times a week, this factor is applied.
• Moderately active (moderate exercise or sports 3-5 days a week):
  • Activity Factor: 1.55
  • Description: If you participate in moderate exercise or sports on most days of the week, this factor is used.
• Very active (hard exercise or sports 6-7 days a week):
  • Activity Factor: 1.725
  • Description: If you have a physically demanding job or engage in intense exercise or sports almost every day, this factor is applied.
• Super active (very hard exercise, physical job, or training twice a day):
  • Activity Factor: 1.9
  • Description: For individuals with extremely high physical activity levels, such as professional athletes or labor-intensive jobs.

To estimate your daily calorie needs using the Harris-Benedict Equation, you would first calculate your BMR based on your age, gender, weight, and height using the appropriate equation (for men or women). Then, you would multiply your BMR by the activity factor that best represents your daily physical activity level.

For example, if your BMR is calculated to be 1500 calories and you have a moderately active lifestyle, you would use an activity factor of 1.55, and your estimated daily calorie needs would be 1500 x 1.55 = 2325 calories per day.

Keep in mind that these activity factors provide estimates, and individual variations may apply. Adjustments may be necessary based on specific circumstances and goals.

Frequently Asked Questions