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[1] [2] The large calorie, food calorie, dietary calorie, or kilogram calorie is defined as the amount of heat needed to raise the temperature of one liter of water by one degree Celsius (or one kelvin). [1] [3] The small calorie or gram calorie is defined as the amount of heat needed to cause the same increase in one milliliter of water.
A moderate energy density would be 1.6 to 3 calories per gram (7–13 kJ/g); salmon, lean meat, and bread would fall in this category. Foods with high energy density have more than three calories per gram (>13 kJ/g) and include crackers, cheese, chocolate, nuts, [10] and fried foods like potato or tortilla chips.
The "grand calorie" (also "kilocalorie", "kilogram-calorie", or "food calorie"; "kcal" or "Cal") is 1000 cal, that is, exactly 4184 J. It was originally defined so that the heat capacity of 1 kg of water would be 1 kcal/°C. With these units of heat energy, the units of heat capacity are 1 cal/°C = 4.184 J/K ; 1 kcal/°C = 4184 J/K.
The calorie is defined as the amount of thermal energy necessary to raise the temperature of one gram of water by 1 Celsius degree, from a temperature of 14.5 °C, at a pressure of 1 atm. For thermochemistry a calorie of 4.184 J is used, but other calories have also been defined, such as the International Steam Table calorie of 4.1868 J.
The typical energy released as heat by a person at rest every 1/60 s (~ 16.6667 ms, basal metabolic rate); about 5,000 kJ (1,200 kcal) / day. The amount of electricity required to run a 1 W device for 1 s. The energy required to accelerate a 1 kg mass at 1 m/s 2 through a distance of 1 m.
For an overall efficiency of 20%, one watt of mechanical power is equivalent to 18 kJ/h (4.3 kcal/h). For example, a manufacturer of rowing equipment shows calories released from "burning" food as four times the actual mechanical work, plus 1,300 kJ (300 kcal) per hour, [16] which amounts to about 20% efficiency at 250 watts of mechanical output.
Mild calorie restriction may be beneficial for pregnant women to reduce weight gain (without weight loss) and reduce perinatal risks for both the mother and child. [11] [12] For overweight or obese individuals, calorie restriction may improve health through weight loss, although a gradual weight regain of 1–2 kg (2.2–4.4 lb) per year may occur.
A kilocalorie is the equivalent of 1000 calories or one dietary Calorie, which contains 4184 joules of energy.The notion that "a calorie is a calorie" is related to the idea that weight maintenance is a result of equalizing calorie input and calorie output, [4] and may lead to the practice of calorie restriction.