The energy from food is always measured in calories, this seems odd: Calories measure the heat energy given off if the food is consumed by fire, but, surely, what an organism is interested in is the energy needed to push things about - work energy. It moves its muscles with work carries out chemical reactions with work. So it shouldn't be calories it should be - at a guess - Helmholtz free energy. New to this forum, hope this is a sensible thing to ask.

They have just used calories for a long time and the calorie count is not 100 percent, if you eat wheat bran, it has a calorie count, but your body absorbs very little. As for helmholtz free energy, that would apply to exersise, the intenal energy change would be more useful

Thanks. It seems to have become important because the retardation of aging and disease by dietary restriction is now officially held to be amount of calories in the food.

I want to know if they are just being sloppy or whether they really mean it.

I believe the theory is on a calorie restriction, cells that need replacement may wait for the materials to do such, so the delay spreads the finite cell division/replacement over a longer period. Probably much more to it.

Never heard of that, that's very interesting. But, again, calories is not the right measure surely - it has nothing to do with raw materials.

Heat is the lowest point on the energy hill; it's whats left after work is done. No energy, no work, no heat.

You can't cheat the system. The universe has been doing it this way for a loooong time and it's not likely to change any time soon.

Calories measure the heat energy given off if the food is consumed by fire? Perhaps you mean that in lab settings, the term calorie is used to express the amount of heat or energy it takes to raise the temperature of 1 gram of water 1 degree C ? The word 'calorie' is used in other areas other than how we associate it with food, but it can be applied to anything containing energy. A calorie simply means a unit of energy which makes it easier for people to calculate how many energy units (calories) in food their body needs to run efficiently.


Absolutely. The body gets this energy from food and the number of calories in a food is a measure of how much potential energy that food contains. In one gram, carbohydrates have 4 calories, protein 4 calories, fat 9 calories.

Sure, since thermodynamics (Thermodynamics (using or producing heat - Or from the free dictionary online "Characteristic of or resulting from the conversion of heat into other forms of energy") comes into play when a system changes its thermodynamic state. Heat/thermodynamics is involved in HFE, just as it is in calories.. same outcome without all the calculating. There's so much that depends on a person's state of health.. are we ever sure how much we're truly absorbing the nutrients and energy from food? With that said, is going through all the HFE calculating for each food source really worth the time when using the term calories is just as adequate?

https://scienceworld.wolfram.com/physics/HelmholtzFreeEnergy.html
Personally, I don't think it's worth the time to do all the calculating to figure out the actual HFE in each food source as our bodies are rarely at a 'constant' and it would only be a 'potential energy' estimate, as it is in calories.

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I think really it is still a good unit of measurement for your every day person to at least have a grasp of the amount of energy needed to power the body!

Not everyone is as well educated as some people on this forum and this is a simplified version to help people relate to the food they eat.

People need to be better educated about the nutritional value of their food rather than just applying number systems to it...