Science question about fat burning

[BrokenBricks]

so i'm figuring direct calorimetry would be constant measuring of exhaled gases?

No, direct calorimetry is when you directly measure the production of heat while accounting for any actual work done. Burning a gram of sugar in a closed vessel and seeing how hot the contraption got would be direct calorimetry. Doesn't work so well with people as you would imagine.

Indirect implies using either O2 or CO2 as proxies for energy expenditure. This is possible because all human energy production relies on consumption of O2 and production of CO2 in fixed ratios. (Anaerobic metabolism does not, but a consequence of homeostasis is that your body will dispose of the products of anaerobic metabolism by aerobic means, just at a delay, so all expenditure is still accounted for with O2 or CO2).

To understand why you can use O2 or CO2 all you really need to do is look at the chemical equation for glucose catabolism.

C6H12O6 (glucose) + 6O2 = 6CO2 + 6H20

This reaction does not take place in the body, but it is the sum of the reactions. You can see that there are 6 O2 consumed and 6 CO2 produced for each glucose molecule. If you know either the amount of O2 consumed *or* CO2 produced you know how much glucose you consumed.

Oh, I didn't answer the question fully. So if you want to know *total* calories burned or O2 used or CO2 produced (all equivalent in terms of information) then you need to add up *all* of the CO2 or O2. So either you do constant measuring or you confine the gases to some space and measure once (lets say i locked you in an air tight room and had you breathe for an hour. I don't need to measure in real time to know how much O2 you sucked up).

Edit: I got beat to it.

[MuscleScience]

No, direct calorimetry is when you directly measure the production of heat while accounting for any actual work done. Burning a gram of sugar in a closed vessel and seeing how hot the contraption got would be direct calorimetry. Doesn't work so well with people as you would imagine.

Indirect implies using either O2 or CO2 as proxies for energy expenditure. This is possible because all human energy production relies on consumption of O2 and production of CO2 in fixed ratios. (Anaerobic metabolism does not, but a consequence of homeostasis is that your body will dispose of the products of anaerobic metabolism by aerobic means, just at a delay, so all expenditure is still accounted for with O2 or CO2).

To understand why you can use O2 or CO2 all you really need to do is look at the chemical equation for glucose catabolism.

C6H12O6 (glucose) + 6O2 = 6CO2 + 6H20

This reaction does not take place in the body, but it is the sum of the reactions. You can see that there are 6 O2 consumed and 6 CO2 produced for each glucose molecule. If you know either the amount of O2 consumed *or* CO2 produced you know how much glucose you consumed.

Yeah that is a very important assumption...

I would be interested in where you think protein fits into energy usage and exercise. Just wondering what camp your in on this and I think you will know what I mean.....

[BrokenBricks]

Yeah that is a very important assumption...

I would be interested in where you think protein fits into energy usage and exercise. Just wondering what camp your in on this and I think you will know what I mean.....

No I'm not sure what you mean. Just full disclosure I am a Biochemistry major and doctor in Emergency Medicine (not done with residency). My exposure to most of this is either related to my undergrad degree or at 2-3 degrees of separation via medical school. You are going to be way more hip to the technical details than I am (and practical details for that matter). I'll take your word on most of this jazz. You just take my word on the infection thread, heh. (as you generously have)

[MuscleScience]

No I'm not sure what you mean. Just full disclosure I am a Biochemistry major and doctor in Emergency Medicine (not done with residency). My exposure to most of this is either related to my undergrad degree or at 2-3 degrees of separation via medical school. You are going to be way more hip to the technical details than I am (and practical details for that matter). I'll take your word on most of this jazz. You just take my word on the infection thread, heh. (as you generously have)

Oh I will admit when my knowledge is lacking somewhere. The first thing you learn in science and medicine as well is when your going to be humbled by someone that has more knowledge on specific subject. If you dont it can be a bad scene as I am sure you have seen.....

I thought the way you were talking that you were some sort of Physiologist which i guess you are. Actually if your up for it, I wanted to write a more technically sound thread about the risk of infection. But I wanted to make it were the common person on here could understand it and use terms that the lay person would know. Your obviously much more experience in that realm and i think you could add valuable insight on the matter.

What I was meaning by the protein question is that the last few Exercise Physiology conferences I have attended had something on how gluconeogensis has been under represented in caloric expenditure. There are some very divided camps on the issue. If you had been to them you would know what I mean....LOL

[BrokenBricks]

I'm not sure what I could contribute to a discussion of infection. It is important for people to understand that while using sterile technique and pharmacy grade drugs their risk of infection is vanishingly small. While using underground drugs and shabby technique they are essentially IV drug users. I am not making a moral distinction but a medical one. They are at risk of limb and life threatening infections and at the first hint of a problem they need to see a doctor and not consult the masses on AR.