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I have read in many biology textbooks and scientific journals that "you create your own bodyweight in ATP each day", but they are all just stated as facts. I have yet to see a study or article that explains how this was determined and what assumptions or observations were used.

For example in the Wikipedia ATP entry "Other processes regenerate ATP so that the human body recycles its own body weight equivalent in ATP each day." This has a footnote which links to Opening and Closing the Metabolite Gate in PNAS. Once again it is just stated as a fact "On any given day you turn over your body weight equivalent in ATP" this time with no footnote.

Has anyone come across anything with actual calculations of how this was determined? Is it based on calories eaten, or oxygen consumed, or extrapolation from a single cell, or something else?

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    $\begingroup$ If this doesn't work out as a question here on biology, then our sister-site Skeptics would certainly take it. You should take the tour and refer to the help center on each site before posting (in an ideal world). $\endgroup$
    – Jiminy Cricket.
    Commented Jun 15, 2022 at 4:25
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    $\begingroup$ As @Domen demonstrates in his answer, it is quite easy arithmetically to come up with this sort of statement. But why are you interested in it? It is just hyperbole used by the self-important to imply their topic is of importance. It may or may not be, but this sort of thing doesn’t make it so. $\endgroup$
    – David
    Commented Jun 15, 2022 at 19:34
  • $\begingroup$ Hi @david, I agree with you that the weight part of this is stupid. I think it misses the really impressive part which is how many times the body is converting ADP to ATP. Something like 6x10^25 a day, or 150 million /every cell in the body (excluding RBCs) /second ! I asked my question because the "body weight in ATP" is commonly stated and I hoped someone knew where it came from. I disagree it is "quite easy" to determine due to uncoupling proteins and mitochondrial membrane permeability that make heat rather than ATP from protons. And other things I am unaware of, hence my question. $\endgroup$
    – Matt Henning
    Commented Jun 16, 2022 at 6:27
  • $\begingroup$ But are big numbers really impressive? How many water molecules are there in a filled tumbler? A lot. And someone will always say "Wow". But one hopes only the first time. Yes, the microscope world is amazing, but the aim of investigating it is rather wider than finding throw-away lines with which to start a lecture. $\endgroup$
    – David
    Commented Jun 16, 2022 at 17:21

1 Answer 1

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The following is a back-of-the-envelope calculation to get a reasonable order of magnitude.

  1. An average person has a daily caloric intake of $E \approx 2000 \; \rm kcal$.
  2. Assume all of the caloric intake goes into the production of $\ce{ATP}$.
  3. The free energy cost1 for synthesizing $\ce{ATP}$ from $\ce{ADP}$ in cellular condition is $\Delta G \approx 50 \; \rm kJ/mol \approx 12 \; \rm kcal/mol$.
  4. Molar mass of $\ce{ATP}$ is $M(\ce{ATP}) \approx 500 \; \rm g/mol$.

Therefore, each day our body produces: $$m(\ce{ATP}) = \frac{E}{\Delta G} \times M(\ce{ATP}) \approx 85\; \rm kg,$$

which is approximately the mass of a human body.

1 http://book.bionumbers.org/how-much-energy-is-released-in-atp-hydrolysis/

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    $\begingroup$ Wow............ $\endgroup$
    – Peter - Reinstate Monica
    Commented Jun 15, 2022 at 18:57
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    $\begingroup$ While this calculation works out, I think it's worth considering that it's kind of bizarre to think this way for any purpose besides trivia. If a 70 kg person takes about 1000 steps over an 8-minute run, you could say that they've moved 1000X their body weight = 70,000 kg in 8 minutes, but has that actually told you anything about how much useful work they've done? Not really, you've come up with an impressive number but it hasn't really meant anything without other context. $\endgroup$
    – Bryan Krause ♦
    Commented Jun 15, 2022 at 19:10
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    $\begingroup$ @BryanKrause Well, yes and no. You example is meaningless, but the ATP production is, I think, not. It means that indeed there is an enormous churning and recycling of compounds in our body. (I for one would not have thought that it's so much, hence my previous comment.) For example, it becomes clear that the ATP, once it has delivered its energy load, must be readily available to be "recharged" -- we see from the numbers that it cannot be metabolized and excreted, for example. $\endgroup$
    – Peter - Reinstate Monica
    Commented Jun 15, 2022 at 19:24
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    $\begingroup$ But note the conjurer’s sleight of hand. The molecular weight is immaterial. If Adenosine had a MW of 1 million, the fact would remain that all that is happening is one phosphate is being added and taken away. I edited the title to try to show how this sort of statement morphs into nonsense. $\endgroup$
    – David
    Commented Jun 15, 2022 at 19:42
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    $\begingroup$ @David True, it's not that 80 kg of mass is synthesized from scratch! $\endgroup$
    – Peter - Reinstate Monica
    Commented Jun 15, 2022 at 19:43

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