Calorie requirement calculator

How is calorie requirement defined?

To calculate the calorie requirement, the total metabolic rate is calculated using the sum of the basal metabolic rate and the active metabolic rate. We explain what this is and how it is calculated below.

Basal metabolic rate (BMR)

The basal metabolic rate is the daily calorie consumption without any exercise. It is calculated here according to the Harris-Benedict equation, which was developed in 1918 and is still considered to be a good guideline for calorie consumption today. The equation takes into account the fact that body weight, height, age and gender influence the basal metabolic rate.

Harris-Benedict equation for calculating the basal metabolic rate

The difference of the first summand is striking, namely 655 for women and 66.5 for men. This can be explained by the fact that the basal metabolic rate in men is more strongly determined by body stature and the associated muscle mass. Men therefore have a higher calorie requirement than women with regard to the basal metabolic rate according to the equation.

Correction of basal metabolic rate with high BMI

If you have a BMI above 30 kg/m², i.e., you are severely overweight, a corrected body weight (Broca Index adjustment) is automatically calculated in the calorie requirement calculation and included in the Harris-Benedict equation. This takes into account the fact that the basal metabolic rate per kilogram of body weight decreases as the body fat percentage increases. Click here for the BMI calculator.

Active metabolic rate

In addition to the basal metabolic rate, the active metabolic rate is also used to calculate the calorie requirement. The active metabolic rate is the amount of energy that is consumed in addition to the basal metabolic rate through work and leisure activities. A reliable calculation of the total calorie consumption is made using the PAL factors ("physical activity level"). For this purpose, five typical lifestyles were defined for adults based on their level of activity. Each of these lifestyles has a PAL factor that is derived from all the usual activities throughout the day. This is multiplied by the basal metabolic rate to calculate the total calorie consumption. The smallest PAL factor indicates the lifestyle with the lowest level of activity. The highest PAL factor of 2.0 to 2.4 is given to people with a high level of physical activity. On average, they consume more than twice their basal metabolic rate in calories.

The PAL factors used to calculate the active metabolic rate in detail

• Sitting or lying only (PAL 1.2)
  People with an exclusively sedentary or recumbent lifestyle (e.g., old, infirm people)
• Sitting, hardly active (PAL 1.4-1.5)
  People with an almost exclusively sedentary way of working and few leisure activities (e.g., people who work a great deal at a desk)
• Sitting, walking and standing (PAL 1.6-1.7)
  People with predominantly sedentary and occasionally standing or walking activities and no or only slightly strenuous leisure activities (e.g., pupils, students, drivers, laboratory assistants)
• Predominantly standing/walking (PAL 1.8-1.9)
  People with predominantly walking or standing jobs (e.g., housewives, waiters, craftsmen, shop assistants)
• Strenuous work/sport (PAL 2.0-2.4)
  People with physically demanding jobs (e.g., farmers, miners, competitive athletes)

Increasing the PAL factor for intensive sport

If you participate in a significant amount of sport or strenuous leisure activities. (4 to 5 times per week for 30 to 60 minutes), the PAL value is increased by 0.3 units for the three activity levels "Sitting, hardly active", "Sitting, walking and standing" and "Predominantly standing/walking".

Total metabolic rate

The total metabolic rate is the sum of basal metabolic rate and active metabolic rate. It describes the amount of energy required per day to maintain weight. It corresponds to the total calculated calorie requirement.

Example: Calculation of the daily calorie consumption

1. Calculation of the basal metabolic rate

Mr. Bold's basal metabolic rate is his daily calorie consumption without any exercise. It is calculated using the Harris-Benedict equation. This equation reads:

By inserting his inputs for weight, height and age into this equation, the following daily basal metabolic rate is determined to be:

1.1 Calculation of the BMI

Dependent on Mr. Bolds's body mass index (BMI) (evaluation of weight in comparison to height), the calculation of the basal metabolic rate using the Harris-Benedict equation may be subject to adjustment. This is because if the BMI is greater than 30, a reducing correction factor for weight is calculated before the equation is applied (Broca Index adjustment). This is because the basal metabolic rate per kilogram decreases with increasing body fat.

1.2 Consideration of the BMI for the corrected basal metabolic rate

As Mr. Bold's BMI is above 30, a correction factor for his weight, the Broca Index adjustment, is first determined. The weight thus corrected is then used instead of his normal weight in the Harris-Benedict equation:

Accordingly, the corrected weight for Mr. Bold is now to be inserted into the Harris-Benedict equation.

2. Calculation of active metabolic rate

As described above, the active metabolic rate is the amount of energy consumed in addition to the basal metabolic rate from work and leisure activities. For this purpose, a certain PAL factor ("physical activity level") is assigned to the predominant activities of a person. This PAL factor then determines the calculation of the active metabolic rate.

Mr. Bold mainly performs office duties. According to this, he receives a PAL factor of 1.45, whereby the following applies: basal metabolic rate × PAL factor=total metabolic rate.