|Detailed method for calculating daily caloric requirements
STEP 1 - Calculate the basal energy expenditure (BEE)
- Basal Energy Expenditure (BEE) is calculated using the Harris-Benedict equation
- English: BEE (calories/day) = 66 + (6.23 X weight in pounds) + (12.7 X height in inches) - (6.76 X age in years)
- Metric: BEE (calories/day) = 66 + (13.8 X weight in kg) + (5.0 X height in cm) - (6.8 X age in years)
- English: BEE (calories/day) = 655 + (4.35 X weight in pounds) + (4.7 X height in inches) - (4.7 X age in years)
- Metric: BEE (calories/day) = 655 + (9.5 X weight in kg) + (1.9 X height in cm) - (4.7 X age in years)
- Patient A is a male, 183 pounds, 73 inches tall, and 39 years old
- BEE = 66 + (6.23 X 183) + (12.7 X 73) - (6.76 X 39)
- BEE = 66 + (1140) + (927) - (264)
- BEE = 1869 calories a day
STEP 2 - Multiply the BEE by a factor of 1.2 or 1.3 to get a sedentary metabolic rate
- Multiplying by 1.2 will give the minimal amount of calories a sedentary person will use in a day doing close to nothing
- Multiplying by 1.3 will give the estimated number of calories a person will burn doing minimal activity during the day (typical daily activities like brushing teeth, etc.)
- Patient A - 1869 calories/d X 1.2 = 2243 calories required to be sedentary all day
- Patient A - 1869 calories/d X 1.3 = 2429 calories required to do minimal daily activities
STEP 3 - Calculate calories burned during various activities
- The Compendium of Physical Activities was developed by scientists to measure the amount of energy that is expended during various activities
- Values for energy expenditure are expressed in METs or "Metabolic Equivalent of Task"
- One MET is defined as 1 calorie/kg of body weight/hour. It is equivalent to the amount of energy a person would expend sitting quietly and doing nothing.
- NOTE: While the basal energy expenditure (BEE) can be calculated using the value of one MET, we prefer to use the Harris-Benedict equation because it is more precise.
- The Compendium of Physical Activities has an extensive list of physical activities and their MET values. It is available online at the link below.
- To calculate the amount of calories burned during an activity, follow these steps:
- 1. Find the MET value for the activity on the list
- 2. Subtract 1 from the MET value of the activity✝. If you are only calculating the calories burned during the activity, you may wish to leave the 1 MET and disregard BEE (Step 1)
- 3. Take the number of minutes you did the activity and convert it to hours
- 4. Multiply the number of hours by the MET value and your weight in kg
- 5. Add this amount of calories to your BEE from STEP 2
- ✝ One MET is subtracted in this step because the MET values in the compendium include basal calories that are burned during the exercise (equal to one MET).
We used the Harris-Benedict equation to calculate basal calories and need to adjust for this.
- Patient weighs 70kg and walked for 30 minutes
- 1. From MET list - walking 2.5 mph, level, firm surface - MET 3.0
- 2. MET 3.0 - 1.0 = 2.0
- 3. 45 minutes / 60 minutes = 0.75 hours
- 4. 0.75 hours X 2.0 METS (calories/kg/hr) X 70kg = 105 calories burned
- 5. Add 105 calories to the value from STEP 2
- Important points about METs
- The compendium is quite extensive and just about any activity can be found
- For weight loss purposes, do not get hung up on calculating calories burned for every little activity you perform
- Only calculate values for major activities and planned exercise (ex. biking, walking, jogging)
- MET values are not perfect. Studies have shown they can sometimes underestimate calories burned during activities. Exercise intensity is also a subjective measure, and this can affect
estimates of calories burned. [3,4]