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Based on the work of Atwater, it became common practice to calculate energy content of foods using 4 kcal/g for carbohydrates and proteins and 9 kcal/g for lipids. [2] The system was later improved by Annabel Merrill and Bernice Watt of the USDA, who derived a system whereby specific calorie conversion factors for different foods were proposed. [3]
The respiratory quotient value indicates which macronutrients are being metabolized, as different energy pathways are used for fats, carbohydrates, and proteins. [1] If metabolism consists solely of lipids, the respiratory quotient is approximately 0.7, for proteins it is approximately 0.8, and for carbohydrates it is 1.0.
The amount of energy required to warm one gram of air-free water from 3.5 to 4.5 °C at standard atmospheric pressure. [b] 15 °C calorie: cal 15: ≈ 4.1855 J ≈ 0.003 9671 BTU ≈ 1.1626 × 10 −6 kW⋅h ≈ 2.6124 × 10 19 eV The amount of energy required to warm one gram of air-free water from 14.5 to 15.5 °C at standard atmospheric ...
Food energy is chemical energy that animals (including humans) derive from their food to sustain their metabolism, including their muscular activity. [1]Most animals derive most of their energy from aerobic respiration, namely combining the carbohydrates, fats, and proteins with oxygen from air or dissolved in water. [2]
(For example, if the calculator determines your calorie goal is 2000 calories, subtracting 10% or 200 calories would give you a goal of 1800 calories per day for weight loss.)
where RQ is the respiratory quotient (ratio of volume CO 2 produced to volume of O 2 consumed), is 21.13 kilojoules (5.05 kcal), the heat released per litre of oxygen by the oxidation of carbohydrate, and is 19.62 kilojoules (4.69 kcal), the value for fat. This gives the same result as the Weir formula at RQ = 1 (burning only carbohydrates ...
Macronutrients are defined as a class of chemical compounds which humans consume in relatively large quantities compared to vitamins and minerals which provide humans with energy. Fat has a food energy content of 38 kilojoules per gram (9 kilocalories per gram) proteins and carbohydrates 17 kJ/g (4 kcal/g).
Carbohydrates and proteins provide 17 kJ approximately (4 kcal) of energy per gram, while fats provide 37 kJ (9 kcal) per gram. [8] However, the net energy derived from the macronutrients depends on such factors as absorption and digestive effort, which vary substantially from instance to instance.