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Water has calories


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Does water have calories? My friend thinks so because joules can be converted to calories and water has energy (joules). I disagree because saying such is akin to saying "a line has meters" rather than "a line has length" which is improper, therefore so is "water has calories." Who is right here, and why?

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Calories that can be used by human body, depends on difference between temperature of drink and temperature of your body.

4.1855 J/K*g * mass_of_water * ( temperature_of_water - 36.6 ) = energy that you can gain because of drinking just water.

But typical e.g. hot tea has no more than 40-50 C, so put inputs in equation, and you have 4.1855 * 250 g * (50-36.6) = 14 kJ of energy.

 

4 minutes ago, dimreepr said:

Water has no 'chemical' energy and therefore no calories without input. 

1 calorie = energy needed to increase temperature of 1 gram of water by 1 degree. From definition of calorie.

https://en.wikipedia.org/wiki/Calorie

 

Edited by Sensei
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7 hours ago, Sensei said:

4.1855 J/K*g * mass_of_water * ( temperature_of_water - 36.6 ) = energy that you can gain because of drinking just water.

But typical e.g. hot tea has no more than 40-50 C, so put inputs in equation, and you have 4.1855 * 250 g * (50-36.6) = 14 kJ of energy.

I assume the original post was referring to "food energy", something that we get through cellular respiration and water in on itself does not have any calorific value.

https://en.wikipedia.org/wiki/Food_energy

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19 hours ago, Mrflapjack said:

Does water have calories? My friend thinks so because joules can be converted to calories and water has energy (joules). I disagree because saying such is akin to saying "a line has meters" rather than "a line has length" which is improper, therefore so is "water has calories." Who is right here, and why?

The caloric (food) value assumes combustion. You can literally burn foods to determine this.

You can't burn water.

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While burning

On 28.02.2018 at 12:30 PM, swansont said:

The caloric (food) value assumes combustion. You can literally burn foods to determine this.

You can't burn water.

Water and carbon dioxide gases are results of burning material to check its caloric (food) value. But energy released during this reaction is in e.g. kinetic energy of newly created molecules. Liquid water particles at 100 C has higher e.g. kinetic energy than water at 20 C, or 36.6 C. During collision with "colder" molecule, kinetic energy is partially or fully transferred to it (elastic/inelastic scattering)

Edited by Sensei
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2 hours ago, Sensei said:

While burning

Water and carbon dioxide gases are results of burning material to check its caloric (food) value. But energy released during this reaction is in e.g. kinetic energy of newly created molecules. Liquid water particles at 100 C has higher e.g. kinetic energy than water at 20 C, or 36.6 C. During collision with "colder" molecule, kinetic energy is partially or fully transferred to it (elastic/inelastic scattering)

Which is irrelevant to the discussion. The food calorie content is based on the combustion of the material, which is why water is said to have no calories. It can't undergo a combustion reaction. It is a product of such a reaction.

Will your body burn calories heating up water (or better yet, ice)? Possibly. But that's a separate discussion.

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5 minutes ago, swansont said:

Which is irrelevant to the discussion. The food calorie content is based on the combustion of the material, which is why water is said to have no calories.

OP nowhere said he is interested in just "food calorie". He said about "calorie". We're in science part of forum, so I am interpreting it as "calorie = (historical) unit of energy".

 

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2 minutes ago, Sensei said:

 

OP nowhere said he is interested in just "food calorie". He said about "calorie". We're in science part of forum, so I am interpreting it as "calorie = (historical) unit of energy".

 

But water has no energy, whatever the unit, without input.

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5 minutes ago, Sensei said:

OP nowhere said he is interested in just "food calorie". He said about "calorie". We're in science part of forum, so I am interpreting it as "calorie = (historical) unit of energy".

"Does X have calories?" (or "how many calories does X have?") is a pretty clear indication that we are talking about food. Because when we talk about energy content we say energy, not calories. And even if not, it would be the inherent energy content, on a chemical level.

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7 minutes ago, dimreepr said:

But water has no energy, whatever the unit, without input.

You omitted essential parameter. Temperature of water.

If you eat ice cream, or ice, it has <0 C, human body has to spend energy to unfreeze it and increase to ambient temperature of body.

If you drink 50 C hot tea. That energy in hot drink does not disappear. Remains in your body, increasing temperature of your body.

 

Does water has food calorie? No it doesn't have food calorie.

Does hot water has energy? Yet it does. 4.1855 [J/K*g] * mass_of_water [g] * ( T_of_water - T_of_your_body ) [K]

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A food calorie is actually a kilocalorie of energy. Otherwise I would simply have a nice cold beer and lose weight.

(after it goes through my system)

 

So a litre of water at 38 C would net me 1 food calorie equivalent (1 degree above my body temperature)

A litre of water at 0 C would save me 37 calories worth of dieting

But it has no actual food calories as mentioned above.

Edited by J.C.MacSwell
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2 hours ago, J.C.MacSwell said:

A food calorie is actually a kilocalorie of energy. Otherwise I would simply have a nice cold beer and lose weight.

(after it goes through my system)

 

So a litre of water at 38 C would net me 1 food calorie equivalent (1 degree above my body temperature)

A litre of water at 0 C would save me 37 calories worth of dieting

But it has no actual food calories as mentioned above.

Reminds me of the "Scotch on the Rocks" diet.   It was based on the idea that there were a smaller number of Calories in a scotch on the rocks than the calories your body expends bringing the consumed drink up to body temp.  The trick was in that fact while perfectly true, a Calorie is actually a kilocalorie  and equal to 1000 calories.

Edited by Janus
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19 hours ago, Sensei said:

You omitted essential parameter. Temperature of water.

Temperature is not an intrinsic property of water, or any atom or molecule, it is a property of the environment.

14 hours ago, J.C.MacSwell said:

A food calorie is actually a kilocalorie of energy. Otherwise I would simply have a nice cold beer and lose weight.

(after it goes through my system)

 

So a litre of water at 38 C would net me 1 food calorie equivalent (1 degree above my body temperature)

A litre of water at 0 C would save me 37 calories worth of dieting 

Possibly. Your body's temperature varies throughout the day, so it's a bit harder to be sure you would burn an extra 37 calories, or if that would be taken care of with what your body is burning anyway.

 

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10 hours ago, swansont said:

 

Possibly. Your body's temperature varies throughout the day, so it's a bit harder to be sure you would burn an extra 37 calories, or if that would be taken care of with what your body is burning anyway.

 

Yeah. I think it stands as part of the equation, but there are a lot of interdependencies involved. Best to jog a couple miles before relieving the kidneys...just to get that core temperature up!:D

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