Calories

ACRONYMS AND DEFINITIONS

ADA - American Diabetes Assoc

BEE - Basal energy expenditure. The amount of energy the body uses at rest.

BMI - Body mass index

Calories and kilocalories - In the context of food, these terms are interchangeable

MET - Metabolic equivalent of task. One MET equals 1 calorie per kilogram of body weight per hour

USDA - United States Dept of Agriculture

1 kg = 2.2 lbs

CALORIES AND BODY WEIGHT

A person's weight is a product of the amount of calories they consume minus the amount of calories they expend

Calories consumed from food - calories burned through activity = net gain/loss of calories

If a person consumes more calories than they expend, they will have a net gain of calories, and the body will store these calories as fat
If a person consumes fewer calories than they expend, then the body must utilize stored energy (fat) in order to meet energy demands
NOTE: In the context of food, "kilocalories" and "calories" mean the same thing and are interchangeable

CALORIE EXPENDITURE

Under normal conditions, there are three components to a person's daily caloric expenditure

Basal Energy Expenditure

Amount of energy required for the body to sustain normal life processes - breathing, tissue metabolism, etc.
This is dependent on a person's height, weight, age, and sex

Physical Activity

Calories burned during activities
Highly variable between individuals

Thermic effect of food

Energy expended by the body to process food for storage and use
Accounts for about 8 - 10% of daily energy expenditure [1]

CALCULATING DAILY CALORIC REQUIREMENTS

Detailed method for calculating daily caloric requirements
NOTE: The following steps can be performed using our calorie calculator
STEP 1 - Calculate the basal energy expenditure (BEE) Basal Energy Expenditure (BEE) is calculated using the Harris-Benedict equation Males 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) Females 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) Example: 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.) Example: 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. Compendium of Physical Activities website 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) calculated above) 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. Example: 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]

Detailed method for calculating daily caloric requirements

NOTE: The following steps can be performed using our calorie calculator

STEP 1 - Calculate the basal energy expenditure (BEE)

Basal Energy Expenditure (BEE) is calculated using the Harris-Benedict equation

Males

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)

Females

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)

Example:

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.)

Example:

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.

Compendium of Physical Activities website

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) calculated above)
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.

Example:

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]

Simple method

A simpler, less exact method of calculating daily calorie expenditure uses the Harris-Benedict equation for BEE, and then multiplies this number by a factor based on a person's estimated activity level
An interactive calculator is available at the USDA website - USDA calorie estimator
Estimated activity levels are defined on the website

Calorie calculator

See calorie calculator for an online calculator that performs the calculations for the detailed method above

CALORIE DEFICIT FOR WEIGHT LOSS

Calorie deficit

In order to lose weight, a person must consume a daily deficit of calories
In general, the following is true:

In overweight adults with BMI > 27:

500 calorie deficit a day for 7 days will produce one pound of weight loss on average
A 1000 calorie deficit a day for 7 days will produce 2 pounds of weight loss on average, and so on

As body weight decreases, further weight loss will require a larger deficit because the BEE decreases (see calculate BEE above). More calorie restriction or increased activity is required. [5]

Low-calorie diet method

Low-calorie diets will lead to weight loss in most overweight adults
This method only requires that an individual count the number of calories they are consuming each day

Low-calorie diet

A diet that consists of 800 - 1500 calories a day is considered a "low-calorie diet" and will lead to weight loss in most overweight adults

Very low-calorie diet

Diets that consist of < 800 calories a day are considered "very low-calorie diets"
These diets are not recommended because they are difficult to maintain and can lead to vitamin and mineral deficiencies [5]

CALORIE CONTENT IN FOODS

Food labels

For most store-bought foods, calorie content can be found on the label

Restaurants and fast food

Many restaurants and fast food establishments now have calorie contents posted on their websites
Some states require that restaurants and fast food businesses post calorie contents of their foods
The USDA food database contains the calorie content of some fast food and restaurant items - USDA food composition database

Calorie databases

There are a number of websites that provide the caloric content of foods. Some good examples are provided below.

USDA food composition database - extensive nutritional information about numerous foods including restaurant foods
myfitnesspal - commercial website that has extensive database of food calorie content
Lose it! - commercial website that has extensive database of food calorie content

MACRONUTRIENTS AND ENERGY

There are 2 main nutritional categories:

Macronutrients - fats, protein, carbohydrates
Micronutrients - vitamins and minerals

Macronutrients

Only macronutrients provide calories
Macronutrients consist of fats, protein and carbohydrates
See the links below for an extensive review of each

BIBLIOGRAPHY

1 - PMID 16978504
2 - PMID 10993420
3 - PMID 15831804
4 - PMID 17558194
5 - PMID 9813653

CALORIES