CALORIES

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• 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 calorie surplus, and the body will store these calories as fat. If a person expends more calories than they consume, the body will utilize stored energy (i.e., fat) to meet energy demands.
• NOTE: In the context of food, "kilocalories" and "calories" are interchangeable

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• Under normal conditions, there are three components to a person's daily caloric expenditure
• Basal Energy Expenditure (BEE)
• BEE is the amount of energy required for the body to sustain normal life processes (e.g., breathing, tissue metabolism). It 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
• The thermic effect of food is the energy it takes to process food for storage and use. It accounts for about 8 - 10% of daily energy expenditure. [1]

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) 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 is a 39-year-old male who weighs 183 pounds and is 73 inches tall 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 gives the minimal amount of calories a sedentary person uses in a day doing close to nothing Multiplying by 1.3 gives the number of calories a person burns doing minimal daily activities (e.g., brushing teeth, eating) Example: Using our patient from Step 1 we have the following: 1869 calories/d X 1.2 = 2243 calories required to be sedentary all day 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 provides estimates of energy expenditure during various activities. Values are expressed in "Metabolic Equivalents of Task" (METs), with one MET equaling 1 calorie/kg of body weight/hour. An extensive list of MET values for various physical activities is available at the link below. Compendium of Physical Activities website The following steps are used to calculate the number of calories burned during an activity: 1. Find the MET value for the activity on the list 2. Subtract one from the MET value.✝ (for total calories burned during the activity, i.e., activity calories + BEE, do not subtract one) 3. Take the number of minutes the activity was performed and convert it to hours 4. Multiply the hours by the MET value and weight in kg 5. Add these calories to the BEE from STEP 2 ✝One MET is subtracted in this step because MET values in the compendium include BEE during the exercise, which is equivalent to one MET. We calculated the total daily BEE with the Harris-Benedict equation in Step 1, so we must 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 extensive, and just about any activity can be found. For weight loss purposes, only calculate calories for major activities and planned exercise (e.g., biking, walking, jogging). MET values are only estimates, and studies have shown they can sometimes underestimate calorie expenditure. Exercise intensity is also subjective, leading to inaccurate calculations in some cases. [3,4]

• Simple method
• A simpler, less exact method of calculating daily calorie expenditure can be done by taking the BEE from the Harris-Benedict equation and multiplying it by a factor based on a person's estimated activity level. An online tool that performs the calculation is available here - USDA calorie estimator

• Calorie calculator
• See our calorie calculator to perform the calculations for the detailed method above

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• Calorie deficit
• To lose weight, a person must consume a daily deficit of calories. In general, the following is true:
• For overweight adults with a BMI > 27:
• A 500 calorie per day deficit for seven days will produce an average weight loss of one pound. A 1000 calorie per day deficit for seven days will produce an average weight loss of two pounds, and so on.
• As body weight decreases, further weight loss requires more calorie restriction or expenditure because BEE declines, reducing calories burned at rest. [5]

• Low-calorie diet
• A diet containing 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
• A diet containing less than 800 calories a day is considered a very low-calorie diet. These diets are not recommended because they are difficult to maintain and can lead to vitamin and mineral deficiencies. [5]

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• Almost all store-bought foods list calories on their labels, and restaurants with twenty or more locations are required by law to list caloric values on their items. A number of websites and apps (see below) offer searchable databases that contain extensive nutritional information, including calories, on many foods. Some can be searched by simply scanning the product's barcode with a smartphone.


• Apps and websites that provide calorie information
• USDA food composition database - government-run database with extensive information, including restaurant foods
• myfitnesspal - commercial website and app with extensive database
• Lose it! - commercial website and app with extensive database
• MyNetDiary - commercial website and app with extensive database

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• Most calories come from macronutrients, which are fats, proteins, and carbohydrates
• Carbohydrates - 4 calories/gram
• Fats - 9 calories/gram
• Protein - 4 calories/gram
• Alcohol - 7 calories/gram

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