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Calculate Energy Intake

  1. Dec 20, 2015 #1
    I've read somewhere that 100 g of tomatoes have approximately 1 g protein, 2.6 g carbohydrates and 0.2 g fat. So it has 4*1 + 4*2.6 + 9*0.2 = 16.2 kcal

    A fried egg (~50 g) has 89 kcal, 4 g protein, 0.4 g carbohydrates, 6.7 g fat. So it has 4*4+4*0.4+9*6.7 = 77.9 kcal

    The sum of the kcals is 16.2 + 77.9 = 94.1 kcal
    I have to write the total of the energy intake. Is it the same as the sum of the kcals, 94.1 kcal?
    If not, then how can I calculate it?
  2. jcsd
  3. Dec 21, 2015 #2


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    Yes. Energies can be added. :smile:

    In fact you have used that twice already when adding up the contributions from the constituents...
  4. Dec 21, 2015 #3

    jim mcnamara

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    Staff: Mentor

    In your example: total energy intake is the sum of the kcal calculation for each food item, summed over all food items.

    If you are taking a nutrition course note:

    1. Food antagonisms and environmental/genetic factors (bioavailability) reduce the uptake of macronutrients: fat, protein, carbohydrate content. Example: phytates in raw, or undercooked legumes.
    This talks mainly about phytates and micronutrients. Micronutrient deficiencies can lead to reduced uptake/usage of macronutrients.

    2. 2.2kg of your body weight comes from gut bacteria. They consume food energy and alter uptake rates of some nutrients + or -.

    3. Not all of what you eat is "yours", so to speak.

    FWIW - a lot of calorie data originated from data based on finding the heat of combustion of constituents of food items using a bomb calorimeter.

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