This may seem like an obvious question to a lot of people but I haven’t been able to find the answer anywhere. Does any of the mass you lose while exercising come about through a means other than defecation (ignoring the
effects of water loss)? In other words, do you shed any of those pounds by breathing out the break-down products of metabolism? If so, how much is expelled through respiration?
Thanks
Here’s the way it works: When you breathe in, you inspire. When you don’t breathe in, you expire.
Fat is used by the body for fuel. You don’t breathe the pounds out. You expend them as energy when you fuel your muscles. That’s where the heat comes from. You are metabolizing.
tcburnett’s answer sounds like you lose weight through e=mc[sup]2[/sup]… Actually you do breathe out a lot of the atoms. Food and stored body fat are mostly water, hydrogen and carbon. The body burns hydrogen and carbon and produces water and carbon dioxide, just like your car does. The water is lost through sweat, breath and urine. Carbon dioxide comes out of your mouth.
You’re forgetting an orifice…
Think of metabolism as an oxidation process (which it is …until someone proves me sorely wrong.) Glycogen (does everything have to be converted into glycogen first?) and oxygen are consumed, leaving carbon dioxide and other wastes. The carbon dioxide gets expelled through your lungs. The other wastes are extracted at the kidneys and sent to the bladder, then the urethra, to be pissed away, like the time that I could have spent on a biochemistry course…
scr4, is it that complete of a reaction?
Thanks to those who have answered so far.
tcburnett: Not that simple, you don’t lose a lot of your mass through heat when you exercise. Most of your mass during weight loss is lost by shedding the waste products of metabolism one way or another - it’s a chemical process. Most chemical processes don’t turn matter into energy or energy into matter. The number of atoms involved usually stay the same, it’s just the bonds between them that change. (Don’t you remember chemistry class?)
My question concerns WHICH way you shed the most mass, respiration, or defecation and the approximate proportions thereof. I’m hoping some expert that understands my question will be able to answer.
P.S. Cornflakes: There aren’t a whole lot of side products in your urine except for ammonia and water - I think the amount of mass pissed away is negligible, otherwise you’d have to pee more when you exercise (actually, I’ve noticed the opposite is true because of the water evaporated when you sweat) which is why I didn’t include it.
What does the body defecate besides waste products from digestion? Except for what you ate in the last day or so, I don’t think that you can lose weight this way.
Cecil addressed this topic here: http://www.straightdope.com/classics/a3_144.html
Every chemical reaction converts matter to energy via e=mc^2, although it’s usually immeasurably small.
Arjuna34
You don’t lose fat through defication. That is just what you could not digest. Once you digest something, you use it or store it. Extra storage is fat. When you exercise enough that your body needs to call upon its fat reserves, it’s broken down. Some (most?) of it is converted into energy (used up to move a muscle/lost as heat), some of it goes to water/carbon dioxide, and I suppose there are some other byproducts.
“You don’t lose fat through defication.”
You haven’t tried Olean.
Interesting, if you don’t eat but do a lot of exercising, you’ll start Ketoning. The byproducts of it makes your breath stink too.
> The other wastes are extracted at the kidneys and sent to the bladder
Another reason it’s good to drink lots of water.
I’m no chemist, but this totally flies in the face of what I was led to understand, Cecil’s comments notwithstanding. (Is that heresy around here? :))
Somebody please correct me if my understanding is not right:
The E=mc[sup]2[/sup] relation refers, literally, to mass (protons, neutrons & electrons) ceasing to exist as mass and instead becoming energy.
I have no handy exothermic chemical reactions sitting here at my disposal to quote, but in any fuel-burning situation, I really didn’t think that was what was going on. No protons, electrons or neutrons disappear during the oxidation reaction of a fuel, which results (I think) in CO[sub]2[/sub], water, and I don’t know what else.
In all of those chemical reactions I studied way back when, the mass had to balance out from one side of the reaction to the other. Some reactions had the products containing a lower amount of stored energy in the bonds than the products had - these are the “exothermic” ones. Fuel oxidation falls into this category. The energy released came from the bonds, not mass-energy conversion.
There are lots and lots of endothermic reactions, too. Same story - matter is not being created here. Mass in = mass out, but the stored energy in the chemical bonds is different.
[Interesting, if you don’t eat but do a lot of exercising, you’ll start Ketoning. The byproducts of it makes your breath stink too.]
[Glycogen (does everything have to be converted into glycogen first?) ]
Ketones are created when your body has almost run out of glyconen, and are basically breakdown of fat - this is what you want to lose weight- so not everything is converted into glycogen- this is the main reason low carb diets works so well for many people- it sets you main fuel to fat.
also there is 2 types of ketosis -
ketosis-acidosis - or something like that - this is the dangerous starvation type when your body is breaking down stored protein (muscle) to create the small amount of glucose requires by your brain, your body runs on fat (ketones) and the blood becomes acidity and causes calcium to leach from the bone. this type causes offensive oder.
benign dietary ketosis - this is the ketosis caused by a low carb diet. the glucose needed by the brain is consumed normally but the body runs on fat. if the intake of carbs is not high enough to create enough glucose, your body breaks down dietary protiens (ingested protiens) instead of stored protiens (muscle) - blood ph is normal, oder is not offensive and some find it pleasent
quote:
I have no handy exothermic chemical reactions sitting here at my disposal to quote, but in any fuel-burning situation, I really didn’t think that was what was going on. No protons, electrons or neutrons disappear during the oxidation reaction of a fuel, which results (I think) in CO2, water, and I don’t know what else.
…
Mass in = mass out, but the stored energy in the chemical bonds is different.
Thank you, you seem to be one of the few persons who remembers chemistry around here. Those of you who think that matter is converted to energy in your body and then just disappears, please get a clue.
That being established, it seems no one thus far knows the answer to my question. Are there any biochemists out there?
brad_d said:
"The E=mc2 relation refers, literally, to mass (protons, neutrons & electrons) ceasing to exist as mass and instead becoming energy.
I have no handy exothermic chemical reactions sitting here at my disposal to quote, but in any fuel-burning situation, I really didn’t think that was what was going on. No protons, electrons or neutrons disappear during the oxidation reaction of a fuel, which results (I think) in CO2, water, and I don’t know what else."
Actually, E=mc2 DOES apply to chemical reactions. It’s just that the quantities of mass involved are so trivial that they don’t show up in the mass-balance equations. The E=mc2
mass losses and gains are accommodated as changes in stored energy in the chemical bonds.
Example: If you burn two moles of hydrogen atoms with one mole of oxygen atoms, you get water plus 242 kJ energy. Your chemistry lessons tell you the mass of the products is the same as that of the reactants. In fact, if you use E=mc2 on the 242 kJ you can work out that the products weigh 0.00269 micrograms less than the reactants, which you can safely ignore.
E=mc2 ALWAYS applies to energy changes. A rubber band gains a tiny amount of mass when you stretch it, because you are storing energy in the atomic bonds.
As to weight loss, you burn fat and carbohydrate to carbon dioxide and water, then breathe it out and piss it out. That’s it, nothing special going on.
Just read the OP again and PAID ATTENTION this time…
keep it simple - lets say you burn off a mole of glucose on a long run. That’s C6H12O6 if memory serves, so a mole weighs 180 grams. The reaction products are 6 moles of carbon dioxide and 6 moles of water. The water weighs 108 grams, which you lose mainly through pissing although you sweat some of it out as well, and you lose the remaining 72 grams by breathing it out. (The carbon dioxide you breathe out actually weighs 264 grams, but that’s because it incorporates 192 grams of oxygen which you breathed in.)
how does adenine triphosphate fit in to all this?
or does it?
Ok, everyone PLEASE drop the e=mc2 argument, it’s inconsequental. You are missing the forest for the trees. I don’t care about unmeasurable amounts of mass that are lost during chemical reactions. (I’d like to know what part of the molecule’s mass is lost, since the energy in a chemical bond doesn’t weigh anything, but that’s for another discusssion)
Matt I don’t think the answer is as simple as you describe. If what you are saying is true, a person who doesn’t eat won’t defecate at all after a few days. I wonder if hunger strikers stop defecating? According to your scenario, they would. I’m also interested in what proportions the mass leaves the body - your breath carries a lot of water, haven’t you ever seen glass fog up??? Also, is everything you burn just turned into water and CO2?
Rita
[I’d like to know what part of the molecule’s mass is lost, since the energy in a chemical bond doesn’t weigh anything, but that’s for another discusssion]
since you asked, I’d like to take a stab at it.
Mass is not a constant, it has a component that is dependent on it’s relitive velocity. this is what’s preventing you from accererating something to the speed of light using f=ma, the more force you put in usally all goes into accereration but as you approach the S.O.L. more and more force goes into increasing the mass. my guess is the electrons, or more likely the quarks or whatever makes them up are moving really fast and as chemical reactions occure they change their velocity as energy is given off
am I right, do I get a gold star?
Rusalka: That’s absolutely true – if you stop eating, you will stop defecating. The alimentary canal is a one-way organ – it absorbs nutrients from your food. Feces are nothing more than the food you couldn’t digest, along with a large addition of bacteria, which aid in digestion (and also give shit that familiar scent).
Any weight you lose is lost as stated above – it is breathed out, pissed out, radiated away as heat or expended as mechanical energy. As for urine containing little besides urea and ammonia, that’s true – and that’s exactly the point, since those are the liquid end-products of metabolism.
Although it would be nice if we could crap our way to fitness, it just doesn’t happen – all that comes out is what you put in, I’m afraid (minus nutrients and water).