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I find the way we measure calories very interesting: place the food in a metal box filled with oxygen, immerse the box in water, make the food explode so that i

I find the way we measure calories very interesting: place the food in a metal box filled with oxygen, immerse the box in water, make the food explode so that it combusts completely, and finally measure how much the water heats up. Rather crude and fun, but that's it, see Bomb Calorimeter. I guess it makes sense in retrospect, how else would you do it? They usually just measure standard basic ingredients, then you roughly match them to your recipe and add it up. No wonder food labelling is just a ballpark.

djtango 2y ago
I'm not convinced calorimetry is particularly useful for any nuanced diet planning. We can't eat wood (or coal) but they're very calorific when measured via bomb calorimetry.
- Ekaros 2y ago
  I was thinking of methane as input. But what about it as output? How much does leave the system? And should this not be in calories "out" column, but I don't think that is usually counted there...
  - djtango 2y ago
    Could you elaborate on what you mean? What does methane have to do with this and what is the "out" column? Calorimetry is just measuring the heat transfer from combustion, usually by measuring the temperature change of a known quantity of water in the classical experiment. You perform versions of it in high school and undergrad Calories are just a unit of energy, and heat can be related back to energy (joules for people using SI)
    - Ekaros 2y ago
      Well some of the food we eat generates flatulence of which 7% can be methane. Meaning this leaves our system without burning. As such in calorimeter it would be unburned fuel. Meaning that some calories are not absorbed failing the calories in and out equation.
      - djtango 2y ago
        Yes absolutely. Not only that but plenty of our food passes through undigested whatsoever. In theory we can't control that so we can only measure calories ingested, not calories absorbed but it hopefully sheds light on the fact that this is more complicated than just a number
s1artibartfast 2y ago
I think it is an interesting and underappreciated aspect of calorie counting as well. I think calories are a decent first order approximation for foods that humans (and animals) evolved eating, because we are efficient extracting chemical energy. The alternative would be empirical animal studies that look directly at weight as a function of feed. You will note that agribusiness doesn't mess around with calories when money is on the line. Instead relies on empirical data for mass as a function of feed type.

djtango 2y ago

I'm not convinced calorimetry is particularly useful for any nuanced diet planning. We can't eat wood (or coal) but they're very calorific when measured via bomb calorimetry.

Ekaros 2y ago
I was thinking of methane as input. But what about it as output? How much does leave the system? And should this not be in calories "out" column, but I don't think that is usually counted there...
- djtango 2y ago
  Could you elaborate on what you mean? What does methane have to do with this and what is the "out" column? Calorimetry is just measuring the heat transfer from combustion, usually by measuring the temperature change of a known quantity of water in the classical experiment. You perform versions of it in high school and undergrad Calories are just a unit of energy, and heat can be related back to energy (joules for people using SI)
  - Ekaros 2y ago
    Well some of the food we eat generates flatulence of which 7% can be methane. Meaning this leaves our system without burning. As such in calorimeter it would be unburned fuel. Meaning that some calories are not absorbed failing the calories in and out equation.
    - djtango 2y ago
      Yes absolutely. Not only that but plenty of our food passes through undigested whatsoever. In theory we can't control that so we can only measure calories ingested, not calories absorbed but it hopefully sheds light on the fact that this is more complicated than just a number

s1artibartfast 2y ago

I think it is an interesting and underappreciated aspect of calorie counting as well. I think calories are a decent first order approximation for foods that humans (and animals) evolved eating, because we are efficient extracting chemical energy. The alternative would be empirical animal studies that look directly at weight as a function of feed. You will note that agribusiness doesn't mess around with calories when money is on the line. Instead relies on empirical data for mass as a function of feed type.