Is a joule also known in nutrition as a kilojoule?

In summary, a joule is a unit of energy measurement commonly used in physics and other sciences. In nutrition, this unit is also known as a kilojoule, with 1 kilojoule equaling 1000 joules. This unit is used to measure the energy content of food and is often used in dietary guidelines and nutrition labels.
  • #1
5P@N
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I just came across Table 2 on pg 173 of "https://books.google.com/books?id=-rgoqmAF9icC&pg=PA159&lpg=PA159&dq=how+much+mass+would+a+snake+lose+before+it+starves&source=bl&ots=G89wh63BP9&sig=d6QmloQ3sMsOPS9PsPRzMd9s25I&hl=en&sa=X&ved=0ahUKEwj13Y6-2O3JAhVIJR4KHQ-VCyYQ6AEIJzAC#v=onepage&q=how%20much%20mass%20would%20a%20snake%20lose%20before%20it%20starves&f=false ". In the table, it mentioned that studied snakes had lost 55 grams of mass. It also mentioned that they had lost 976.9 "kJ".

Now: does the "kJ" mean kilojoules, or just joules? When I divide 55 by 976.9, I get: 17.75 "kJ" per gram. When I however look up elsewhere what the energy values in joules are for the variously mentioned classes of biological substances the author mentioned (carbohydrates, fats, and proteins), I discover that carbohydrates and proteins have 16.8 joules per gram, whereas fats have 37.8. A proportion of these substances would then form a figure of 17.75 joules, but not kilojoules. There's a difference here by a thousand-fold! Or is it that there's some idiosyncratic and arcane practice in biological sciences to call joules kilojoules? What am I missing here?
 
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  • #2
5P@N said:
When I however look up elsewhere what the energy values in joules are for the variously mentioned classes of biological substances the author mentioned (carbohydrates, fats, and proteins), I discover that carbohydrates and proteins have 16.8 joules per gram, whereas fats have 37.8.
Those values are in kJ/g. See https://en.wikipedia.org/wiki/Food_energy
 
  • #3
So: 1 kJ = 1,000 J?

There isn't some sneaky joule v. Joule distinction as there is between the calorie v. Calorie, right? A joule is a Joule? A cigar is just a Cigar?
 
  • #4
I mean: the kJ as used in nutrition is the same kJ as is used in physics?
 
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5P@N said:
So: 1 kJ = 1,000 J?

There isn't some sneaky joule v. Joule distinction as there is between the calorie v. Calorie, right? A joule is a Joule? A cigar is just a Cigar?
5P@N said:
I mean: the kJ as used in nutrition is the same kJ as is used in physics?
Yes.
 

1. What is a joule and how is it related to nutrition?

A joule is a unit of energy commonly used in physics to measure work and energy. In nutrition, joules are often referred to as kilojoules (kJ). Kilojoules are used to measure the energy content of food, which is important for understanding calorie intake and maintaining a healthy diet.

2. How many kilojoules are in a joule?

One kilojoule is equal to 1000 joules. This means that a joule is a smaller unit of measurement than a kilojoule. When it comes to nutrition, kilojoules are typically used because the energy content of food is much larger than a single joule.

3. Why are kilojoules used in nutrition instead of calories?

Kilojoules are the standard unit of energy used in the metric system, while calories are used in the imperial system. In order to have a consistent measurement of energy in nutrition, kilojoules are used. Additionally, kilojoules are a more precise measurement compared to calories.

4. How many kilojoules should I consume in a day?

The recommended daily intake of kilojoules varies depending on factors such as age, gender, and activity level. Generally, an average adult should consume around 8,700 kilojoules per day. However, it is important to consult with a healthcare professional to determine the appropriate amount for your specific needs.

5. Can consuming too many kilojoules be harmful to my health?

Yes, consuming too many kilojoules can lead to weight gain and an increased risk for health issues such as obesity, diabetes, and heart disease. It is important to maintain a balanced diet and monitor kilojoule intake to maintain a healthy weight and overall well-being.

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