Can you gain weight after exercising?

[dirtymatt]

A co-worker and myself are having an argument with several other co-workers about if it is possible to gain weight after exercising, assuming you do not drink or eat anything while exercising. Ie, you go to the gym, weigh yourself, work out, and weigh yourself again and you have gained two pounds. They both swear it is possible due to either retaining water, or undigested food gets converted to energy or fat. I say that this is not possible. Sure, you can retain water, but if you're not drinking, any water that ends up in your body, had to start in your body. I also don't see how a 1 pound cheese burger can some how become 1.5 pounds of fat.

I can see plenty of ways you can lose weight, sweating, moisture loss from respiration, conversion of stored chemical energy into kinetic energy. I wouldn't expect any of these to acount for a lot of weight loss, sweating being the most.

The only thing I can think of that would cause weight gain would be increased oxygen stored in muscle tissue, but I doubt that could account for a two pound gain.

Am I completely wrong here?

Thanks

[Phishfood]

yes, you can gain weight if you're doing a power-lifting type deal, and not cardiovascular. you're converting calories to muscle. muscle is more dense than fat, and weighs more. if you're running, you're burning more calories but not adding as much muscle. if you're lifting, you're ripping and rebuilding a lot of muscle.

problem is, this is very unlikely. the odds of someone gaining enough muscle mass relative to fat lost to gain weight is highly improbable. in a rigorous workout routine, a person will gain only about 4 kg of muscle.

-Pf

[theyeti]

A co-worker and myself are having an argument with several other co-workers about if it is possible to gain weight after exercising, assuming you do not drink or eat anything while exercising. Ie, you go to the gym, weigh yourself, work out, and weigh yourself again and you have gained two pounds. They both swear it is possible due to either retaining water, or undigested food gets converted to energy or fat.

The only way to gain weight is to drink water or eat food. The only way to lose weight is to shit or piss (or sweat, etc.). Anyone who thinks that food can be "converted" into something of lower mass doesn't understand the first law of thermodynamics.

theyeti

[IanC]

You can loose weight through perspiration, but you cannot gain weight (slight density changes may occur, but nothing significant).

To gain weight, as has been said, you MUST eat or drink something, the weight has to come from somewhere.

As you say, you can gain a tiny amount of weight from the oxygen you breathe in, but it is tiny. You wont store two pounds of oxygen in your muscles.

Perhaps a change of clothing after being at the gym could increase someones apparent weight slightly, and then this was exaggerated.


Ian

[theyeti]

As you say, you can gain a tiny amount of weight from the oxygen you breathe in, but it is tiny. You wont store two pounds of oxygen in your muscles.

Given that for every mole of O2 you inhale, you exhale one mole of CO2, you actually lose weight through respiration. But as you say, it's miniscule.

theyeti

[penumbra]

yes, you can gain weight if you're doing a power-lifting type deal, and not cardiovascular. you're converting calories to muscle. muscle is more dense than fat, and weighs more. if you're running, you're burning more calories but not adding as much muscle. if you're lifting, you're ripping and rebuilding a lot of muscle.

problem is, this is very unlikely. the odds of someone gaining enough muscle mass relative to fat lost to gain weight is highly improbable. in a rigorous workout routine, a person will gain only about 4 kg of muscle.

-Pf

Uh, IIRC, the muscle building (or rebuilding) does NOT take place during the exercise session, but during the rest period following it. Thus, you do not GAIN any muscle until your body has time to recuperate.

Under the conditions given in the OP, i.e., no ingestion of water or food during the exercise session, the subject will not gain weight during said session.

[Dark Knight Bob]

Muscle growth through excecise works like this. You excercise. This damages the muscle tissue stimulating new growth. Sports scientists basically try to figure out the optimum amount of muscle growth you can get with excercise without damaging the muscles so much your body ends up having to simply replace the damaged tissue or worse damaging the muscle beyond any short term repair.

This is hwy you get a variation in how much excercise you should do on certain limbs etc and dependant on your body weight and current muscle size.

[David Z]

Am I completely wrong here?You are completely right here. You can lose a lot of weight from dehydration during a long exercise session, but as other posters have stated... where does the mass come from that would cause you to increase weight, if you aren't eating anything? Did they stick one of the plates in their pocket? They are wrong, you are right... please slap them for me.

From the title of the thread I thought this was going to be a question about whether an exercise regimen can cause you to gain weight over time, which of course it can. This happened to me when I was a skinny kid and I took up running. I went from having no fat and no muscle to having no fat and some muscle. I gained almost 20 pounds. Alarmingly, I also developed weird lumps all over my body, the worst being at the top of the back of my legs. It was a butt!

[Agemegos]

The only way to gain weight is to drink water or eat food.

Indeed. Even though exercise can stimulate the growth of muscle tissue, the mass still has to come from somewhere outside the body. Conservation law.

The only way to lose weight is to shit or piss (or sweat, etc.).

'etc.' includes to breathe. The carbon from foods oxidised in respiration is nearly all disposed of by exhalation of CO2. Inhaled O2 is replaced with exhaled CO2, with the result that the dry mass of exhaled air is 1.5% higher than that of inhaled air. In addition to which a considerable (but variable) proportion of our water losses take place through the lungs, as exhaled air is moister than inhaled air.

[Duck!]

yes, you can gain weight if you're doing a power-lifting type deal, and not cardiovascular. you're converting calories to muscle. muscle is more dense than fat, and weighs more. if you're running, you're burning more calories but not adding as much muscle. if you're lifting, you're ripping and rebuilding a lot of muscle.Surely it wouldn't matter how dense muscle is. All that would mean is that you're the same weight, but you have less volume. You can't convert 1Kg of fat into 1Kg+ of muscle. That would violate
some of the the most basic laws of nature.


Duck!

[Phishfood]

I agree with you guys. I was spitting out some high school gym stuff I remembered, and didn't think.

sorry for making myself look dumb

-Pf

[B_Sharp]

Laws of Thermodynamics, 1st Energy Conservation or 2nd Entropy, do NOT apply, only loosely, because a body working out is an "open" system.

Next then, the only added weight is the chemical processes of breathing in air, then converting some of those air molecules into 'added' mass via amino acids. Measure your lung air capacity times breath rate times duration times efficiency of air to solid.

Gas (breath air) to solid conversion is low.
Liquid (sweating) expelling is high.
Liguid (sweat) contains a high volume conversion of gas.

PV=nRT.

CONCLUSION
Since your body expells far more gas via liquid (sweat) than the intake of solid/liquid via gas (breathe air) conversion, there is NO WAY you will gain weight. :cool:

[penumbra]

I agree with you guys. I was spitting out some high school gym stuff I remembered, and didn't think.

sorry for making myself look dumb

-Pf

No sweat (so to speak) we all suffer brain farts now and then (and mine have become more frequent with age!!)

[walt6]

Perhaps this phenomenon can be explained by not-so-accurate weight scales.

[mirage]

Given that for every mole of O2 you inhale, you exhale one mole of CO2, you actually lose weight through respiration. But as you say, it's miniscule.

theyeti
Actually to go for the nit pick crown of the thread, you breathe out fewer Co2s for Each O2 for fat metabolism (ratio 0.7) than for carbs (ratio 1.0) because of the O and H ratios in them. So the overall value is 0.7-1.0 range and tells you what you've been eating lately.

[scigirl]

Hi dirtymatt,

It is possible to gain weight if you are bulking up more muscle than you are losing fat. Plus, as you start exercising, your caloric intake goes up. I worked in an exercise research lab last year in my "spare time" from medical school, and we often found that people who first started exercise programs would in fact gain a couple of pounds before losing. This is temporary, and goes away eventually, after your basal metabolic rate goes up to help shed the pounds.

If the goal is weight loss: A better way to see if you are losing actual fat weight is to monitor your waist circumference. The fat that's bad for you is stored in your abdominal region.

Adipose tissue: a mediator of cardiovascular risk. (http://0-www.ncbi.nlm.nih.gov.library.uchsc.edu/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12457291)

Anther recent study came out, I'll have to find it, that showed people who are active but slightly overweight are actually more healthy (in terms of cardiovascular factors) than normal weight individuals who are very sedentary.

So the moral of the story is: exercise! ;)

scigirl

[scigirl]

theyeti:
The only way to gain weight is to drink water or eat food. The only way to lose weight is to shit or piss (or sweat, etc.). Anyone who thinks that food can be "converted" into something of lower mass doesn't understand the first law of thermodynamics.

Surely it wouldn't matter how dense muscle is. All that would mean is that you're the same weight, but you have less volume. You can't convert 1Kg of fat into 1Kg+ of muscle. That would violate
some of the the most basic laws of nature.
Of course both of you are correct. However, I think that this is not an ideal way to look at weight loss and energy conversion.

As you start to exercise, your basal metabolic rate increases. Or conversely, let's say you go through menopause. Your BMR decreases. So you can eat the exact same amount of food as you did a year ago and now gain weight. So it's basically like trying to estimate a car's fuel efficiency by the products of the burned fuel while the catalytic converter keeps changing.. A little tougher to do.

And actually you could convert, theoretically, 1 g of fat into 1 g of muscle, if you allow that the body has a liver and other such organs to chip in things. Fat has 9 kcal/g whereas protein has only like 4 or 5. The energy transfer is what needs to balance.

Edited to add: actually you would need to know how much energy it takes to build protein, not break it down. If you need less than 9 kcal/g to build muscle, than you can in fact build muscle from fat, assuming this is being done in a human body and not a test tube.

scigirl

[DNAunion]

Laws of Thermodynamics, 1st Energy Conservation or 2nd Entropy, do NOT apply, only loosely, because a body working out is an "open" system.

They don't?

The law of conservation of mass/energy states that the mass/energy of an isolated system must remain constant. The isolated system here being the universe. The open system of interest is the person's body. So the mass/energy of the open system and it's surroundings must remain constant. If the open system is increasing in mass/energy, then the the surroundings must be decreasing in mass/energy: conservation. This applies perfectly to the discussion: as people said, one would have to eat, drink, or otherwise bring in matter (mass/energy) from the surrounding in order for the body to gain weight. So the question then becomes, during exercise in which a person does not eat or drink anything, what could be entering the body to increase mass/energy by 1 or 2 pounds? Since no one has offered any plausible source, we must conclude that the idea that a person can gain 2 or 2 pounds when exercising - without ingesting anything - is wrong.

And the second law of thermodynamics can be summarized as "you can't break even". Basically, during any transformation of energy from one form to another, some of the energy is degraded into a less usable form. So during exercise, chemical energy in molecules (such as ATP) is transformed into mechanical energy (used to move limbs) and some of the original energy is "lost" as unusable heat. So each "microstep" of exercise decreases the body's overall usable energy a bit, as some energy escapes as heat. Now, if the second law didn't apply, then the body could continue to exercise indefnitely without worrying about energy losses. But that's not the case. According to the second law, since energy - more correctly, mass/energy - is leaving the body, then for the body to even maintain constant mass, it must bring in mass/energy from the surroundings. Again, showing that the original claim that one can gain mass when exercising and not taking in anything cannot be correct.


B_Sharp: Next then, the only added weight is the chemical processes of breathing in air, then converting some of those air molecules into 'added' mass via amino acids.

The main function of breathing in air during exercise is to obtain enough oxygen to allow for continued cellular energy production; it's not for the synthesis of amino acids. (If you do low intensity aerobic exercise, then the oxygen intake is keeping pace with demand; if you do high intensity anaerobic exercise, then oxygen intake cannot keep pace with demand and the muscles use anaerobic mechanisms to sustain contractions: then for a period after exercise, you continue to breathe heavily to make up for the oxygen debt you've established during the anaerobic exercise).

And as at least one other person has pointed out, muscle mass (in the form of the synthesizing of contractile proteins from amino acids) doesn't occur during an exercise session, but afterwards: during periods of rest. So an increase in amino acid production isn't a key event during exercise that might lead to an increase in mass.

[mirage]

Edited to add: actually you would need to know how much energy it takes to build protein, not break it down. If you need less than 9 kcal/g to build muscle, than you can in fact build muscle from fat, assuming this is being done in a human body and not a test tube.You would also have to take into account the significantly bellow perfect efficiency of this process. kcal are what you get burning fat in a flame. The efficiency of glucose to ATP energy transfer is about 40% (I think).

You also can't get around needing your essential amino acids to come from diet, so a straight conversion is not possible.

The early weight gain with exercise programs (starting the day of exercise) is largely due to increased water content of the muscles, i.e. being "pumped up" and replacing the displaced water volume with fluid intake. (Pumped up muscles are largely just because of higher blood flow there. Longer term changes are increased cellular water content in the stressed muscles.)

[scigirl]

I read the original question a little closer,
A co-worker and myself are having an argument with several other co-workers about if it is possible to gain weight after exercising, assuming you do not drink or eat anything while exercising. Ie, you go to the gym, weigh yourself, work out, and weigh yourself again and you have gained two pounds.
Um no that is not possible. Have they documented this actual phenomenon? If so, consider the following:
1) they did in fact drink 2 lbs of water.
2) The scale has a margin of error of greater than 2 lbs.
3) Shoes and clothes off, then shoes and clothes on. Or they weighed themselves with a heavy towel afterward.

In my last reply, I was thinking more of the question "can you gain weight by exercising?" which is "yes" over a period of weeks, etc, with increased food intake, more muscle build-up, increased water retention as mirage mentioned, etc.

[DNAunion]

(Pumped up muscles are largely just because of higher blood flow there. Longer term changes are increased cellular water content in the stressed muscles.)

And two types of hypertrophy.

[liquid]

2 points on this discussion:

Nitpicky one - Some people seem to be confused over what the OP is asking. It appears that the OP is talking about gaining or losing mass in a single exercise session i.e. a physics problem, not anything to do with ody changes through an exercise program.

Not nitpicky one - There are also a few people who obviously know something of the physics, but are getting themselves horrendously confused.

This problem involves the principle of conservation of mass. It is NOTHING to do with the laws of thermodynamics (at least not unless you are trying to figure out particular mass and energy flows or other such details).

You lose energy when exercising. You could even gain energy if you were being gently cooked whilst exercising! None of this has any effect on body mass in itself.

After all, I doubt there's too much E=mc^2 going on!

So all you have to do is analyse mass flows concerning your control volume:

In: Air, Dust.

Out: Exhaled air (as noted above, more mass than intake), dust, blood, sweat, tears, snot, dead hairs, skin cells... you get the idea!

So unless your friends are eating a couple of kilos of dust in their gym air, you can safely say that they are wrong.

[theyeti]

Actually to go for the nit pick crown of the thread, you breathe out fewer Co2s for Each O2 for fat metabolism (ratio 0.7) than for carbs (ratio 1.0) because of the O and H ratios in them. So the overall value is 0.7-1.0 range and tells you what you've been eating lately.

You win! :)

theyeti

[theyeti]

'etc.' includes to breathe. The carbon from foods oxidised in respiration is nearly all disposed of by exhalation of CO2. Inhaled O2 is replaced with exhaled CO2, with the result that the dry mass of exhaled air is 1.5% higher than that of inhaled air

Right, this is just a guess, but I'd bet that you defecate (and piss) more carbon than you breathe out. I've got no numbers to back that up or anything, but it's just a hunch on my part. I'm waiting for someone less lazy than me to prove this right or wrong.

theyeti

[liquid]

The carbon from foods oxidised in respiration is nearly all disposed of by exhalation of CO2

I think maybe you should reread the first clause of that sentence yeti!

So you're just down to certain constituents of piss then.... interestingly enough, that was how Atkins thought you lost weight on his diet.

[dirtymatt]

I read the original question a little closer,

Um no that is not possible. Have they documented this actual phenomenon? If so, consider the following:
1) they did in fact drink 2 lbs of water.
2) The scale has a margin of error of greater than 2 lbs.
3) Shoes and clothes off, then shoes and clothes on. Or they weighed themselves with a heavy towel afterward.

Yikes, thanks for all of the replies everyone. I should have been more clear in the OP, but I did infact mean weight gain imediately after excersizing, ie, weigh yourself, jump on a treadmill for 30 minutes, weigh again. One of my co-workers does say she routinely experiences a 2 pound weight gain after excersizing. She rulled 3 out, this is before showering or changing and says she drinks less thank a few ounces of water, which I don't think would weigh two pounds. I'm sure her clothes are heavier, as she was sweating, but since that sweat had to come from her body in the first place, it shouldn't be able to add weight. I honestly think 2 is the most likely. It seems odd that it would routinely be 2 pounds heavier after excersize, but my experience has been that people tend to remember situations that confirm their theories more often than situations that don't.

Again, thanks to everyone who posted. One more quick question; is it possible to say gain 2 pounds from eating 1 pound of food. Say it's one pound of lard, is it possible to gain more than 1 pound from eating it? To me it seems like it's not. No matter how you change that food's form, it can never increase in weight. Especially since you will lose a good deal of it as waste, and a lot of the energy will go into the actual process of digesting it.

Thanks again.

[theyeti]

I think maybe you should reread the first clause of that sentence yeti!

Er, yeah, I guess if we're talking about respiration, then CO2 is the fate of nearly all the carbon.

So you're just down to certain constituents of piss then.... interestingly enough, that was how Atkins thought you lost weight on his diet.

Well, urea has just as much carbon as nitrogen... :)

theyeti

[theyeti]

Again, thanks to everyone who posted. One more quick question; is it possible to say gain 2 pounds from eating 1 pound of food. Say it's one pound of lard, is it possible to gain more than 1 pound from eating it?

Only if you drink a pound of water.

There's nothing speical about food, it behaves like any other matter. The energy you get from it comes from its chemical bonds. You gain weight when your body takes sugars and fats and converts them into adipose tissue. Or you can build muscle from proteins you eat. (And yes, for all you pedants, you'll build lots of other stuff as you're growing.) But no matter what, you can't gain more wieght than what you eat. Muscle and fat doesn't materialize out of thin air, it must be built from the food you eat. Water will be used for hydrolysis in some cases (as with fat or protein), but again, it doesn't come from nowhere, you have to swallow it.

theyeti

[liquid]

is it possible to say gain 2 pounds from eating 1 pound of food

No. Principle of conservation of mass again. The energy content has nothing to do with it.

[DNAunion]

double post

[Boro Nut]

Can you gain weight after exercising?

Certainly. Every American can gain weight by exercising., their inalienable right to stuff themselves beyond capacity. It's only out of respect for (and in recognition of) your sacred freedoms that we British will reply to a happy 'Have an nice day' with a cheery 'Get stuffed'.

Boro Nut

[DNAunion]

No. Principle of conservation of mass again. The energy content has nothing to do with it.

That's the second time you've mentioned the priniciple of the conservation of mass. I am aware of the law of conservation of matter (from chemistry) and the law of conservation of energy (from physics; which is more accurately described as the law of conservation of mass-energy), but I am not aware of a scientific law of conservation of mass.

To me, you seem to be talking about the law of conservation of matter, since you are considering the difference between the amount of matter taken in and the amount of matter expelled.

[DNAunion]

Not nitpicky one - There are also a few people who obviously know something of the physics, but are getting themselves horrendously confused.

This problem involves the principle of conservation of mass. It is NOTHING to do with the laws of thermodynamics (at least not unless you are trying to figure out particular mass and energy flows or other such details).


The laws of thermodynamics are very key here. Do you not think that bioenergetics applies to exercise?

And consider this. If we discard the laws of thermodynamics, there's nothing to prevent several pounds of mass-energy from just popping into existence inside the person and increasing his/her weight. Everyone here is implicitly relying on the conservation of mass-energy in their explanations.

liquid: You lose energy when exercising. You could even gain energy if you were being gently cooked whilst exercising! None of this has any effect on body mass in itself.


Yes it would. If someone added energy to your body, that additional energy would increase your body's mass. It could not be otherwise. And any energy you lose as heat during exercise does decrease your mass.

liquid: After all, I doubt there's too much E=mc^2 going on!

"E=mc^2 going on" occurs in all kinds of everyday phenonema. Take a bunji cord and stretch it: by your storing potential energy in it you've increased its mass, even though you've not added any atoms. Or take a coal-burning plant: the same amount of mass is converted into energy as occurs in a nuclear power plant for the same yield.

Or more to the point, take chemical reactions that occur in cells. Neither atoms, nor electrons, nor protons, nor neutrons are created or destroyed, yet mass is definitely converted into energy. It's the rearrangement of chemical bonds, which results in changes in binding energy. And if you could measure the mass of the products and the mass of the rectants - using an unbelievably precise scale - for an exergonic reaction, you would find that the products have less mass than the reactants: the missing mass has been converted into energy.

**************************

Now, perhaps you mean the degree of mass-to-energy conversion isn't significant enough to bother with in regards to this discussion about weight. That may be so, but then again, what IS significant enough to account for an actual 2-lb gain in body weight if the person doesn't eat or drink, but exercises? Nothing (assuming g, the acceleration due to gravity, remains constant throughout - as we would expect). For example, the matter balance you and others have been discussing: what is the net effect of all of the matter exchanges? How many pounds? How many ounces? Hoe many grams? It's quite negligible.

liquid:
In: Air, Dust.

Out: Exhaled air (as noted above, more mass than intake), dust, blood, sweat, tears, snot, dead hairs, skin cells... you get the idea!


You bleed when you exercise? You cry when you exercise? I've heard of "no pain, no gain", but wouldn't that be taking it to extremes? : -)

[Agemegos]

Right, this is just a guess, but I'd bet that you defecate (and piss) more carbon than you breathe out.

Perhaps. Anyone care to venture a BoE calculation or cite some evidence?

[Agemegos]

One more quick question; is it possible to say gain 2 pounds from eating 1 pound of food.

Not by itself, of course. But one pound of extra food can cause you to retain more of other food and drink.

For example, if your diet is normally fairly low in carbohydrate, and you eat say four ounces of starch per day for four days in addition to eating and drinking your normal diet, then the extra carbohydrate can elevate your insulin level and reduce your glucagon level. These hormone changes can alter your kidney function, reduce the production of urine, cause you to retain extra water, and make you put on weight at the scale far out of proportion with the extra glucose. But when you return to a low-carbohydrate diet the extr weight will drop off in a few days.

For a sort of example, two years ago I was showing some symptoms of hyperinsulinaemia, and faced a danger of developing type II diabetes. I switched from a conventionally 'good' diet high in complex carbohydrates to a low-carbohydrate diet. My sustained weight loss over the next six months was a kilogram per week (nine pounds per month), and that gives you a fair idea of what I accomplished by reducing my intake of food energy (I did not increase my level of exercise enough to signify). But in the first two weeks I lost a total of 9 kg (20 lb): estimating that two of those kilos represented actual loss of fat, I reckon that I lost 7 kg (fifteen pounds) of retained water in about ten or eleven days by an adjustment to my diet.

[scombrid]

A co-worker and myself are having an argument with several other co-workers about if it is possible to gain weight after exercising, assuming you do not drink or eat anything while exercising.

Breatharians? (http://www.breatharian.com/)

[scombrid]

One more quick question; is it possible to say gain 2 pounds from eating 1 pound of food. Say it's one pound of lard, is it possible to gain more than 1 pound from eating it?

Not directly. 1 pound in cannot be assimilated into body tissue weighing more than 1 pound unless it is combined with something else imbibed.

If you are glycogen depleted (say after a couple of hours of vigorous training) then eating a starchy carb meal plus drinking water will make you gain more weight than just the dry weight of the consumed carbs. When carbs are converted to glycogen and stored in muscle, a lot of water is stored with them. I often gain 5lbs (about 2.6% of my bodyweight) in a day or two when tapering (reduced training load and increased carb intake) for a race. That 5lbs doesn't represent a change in bodymass but instead reflects the glycogen stored in the muscle (and attendant water weight).

[Matt the Medic]

...she drinks less thank a few ounces of water, which I don't think would weigh two pounds.

Water is alot heavier than people think. Of course "weight" can be dependent of factors such as temperature and pressure, but at room temperature, consider:

1 Gallon of Water = 8.33lbs
128 fl. ounces = 1 gallon

A 'few ounces' is a small sum indeed. Lets say she drinks one normal sized bottle of water. That is 20 fl. ounces right there.

SO, 128 fl. oz. H20 = 8.33 lbs
(8.33 / 128) * 20 = 1.30lbs / 20 fl. oz H2O

2 pounds of water would be (128 * 2) / 8.33 = 30.73 fl. oz. -Which would only require her to down 1 and a half normal sized bottles of water; or roughly 90% of one of the slightly larger (but still common) 1Liter(~34 fl oz) bottles.

Downing a 1L bottle while exercising would typically be a conservative estimate based on many exercises. The bottom line is that gaining two pounds could very well be possible provided variables such as loss of fluids through sweat and expiration, accuracy of the scale, and others are accounted for. Ask her to weigh herself on the same scale a third time, but wait several hours after exercising. I would imagine that after evaporation of any remaining water, plus nature taking its course (micturition :) ) her weight would be back down to where it was pre-exercise/consumption. All variables considered.

[Matt the Medic]

Perhaps. Anyone care to venture a BoE calculation or cite some evidence?

Urine typically has <5 mmol / L of CO2. I'm not sure how much else is carbon in other forms, considering nearly every molecule in our body has carbon in some form in it :D.

I dont have any exact sources with me but I recall that in exhalation only ~4% of the air is CO2, but considering that normal lung capacity is somewhere around 4 liters, 4% of that is quite simply 160mL. I don't have to do the conversion to mmol to show that CO2 leaves the body in a far superior quantity via exhalation. :)

Of course carbon and CO2 in stool is an entirely different beast. That has a ton more to do with what you consume and the reactions your food has with your Gi Tract. Many foods such as dairy and medicines such as laxitives actually release CO2 as a byproduct (Gas anyone?)

[Vinnie]

The only way someone can gain weight while working out without eating or drinking something is through a miracle.

Vinnie

[Agemegos]

I dont have any exact sources with me but I recall that in exhalation only ~4% of the air is CO2, but considering that normal lung capacity is somewhere around 4 liters, 4% of that is quite simply 160mL. I don't have to do the conversion to mmol to show that CO2 leaves the body in a far superior quantity via exhalation. :)

I'll attempt the conversion, just to be on the safe side.

160 mL of CO2 per breath by 12 breaths per minute by 60 minutes per hour by 24 hours per day is 2745 L of CO2 exhaled per day.

Divided by approximately 25 L per mol is about 110 mol per day. Each mole of CO2 contains about 12 g of carbon, so a typical person exhales about 1.33 g (2.9 lb) of carbon every day.

I don't know: that figure seems awfully high. Did we take into account the incomplete emptying of the lungs on exhalation?

[Matt the Medic]

I'll attempt the conversion, just to be on the safe side.

160 mL of CO2 per breath by 12 breaths per minute by 60 minutes per hour by 24 hours per day is 2745 L of CO2 exhaled per day.

Divided by approximately 25 L per mol is about 110 mol per day. Each mole of CO2 contains about 12 g of carbon, so a typical person exhales about 1.33 g (2.9 lb) of carbon every day.

I don't know: that figure seems awfully high. Did we take into account the incomplete emptying of the lungs on exhalation?

No we didn't but I think you more than accounted for that by using the minimum textbook adult respiratory rate. I can tell you from professional experience most adults' respiratory rate is closer to 16-20 on average.

[Matt the Medic]

The only way someone can gain weight while working out without eating or drinking something is through a miracle.

Vinnie

Or to skip to the point, it is impossible. :)

[badger3k]

Or to skip to the point, it is impossible. :)

Nonsense. I gained 20 lbs in one workout.

Then I put down the dumbbell. :)

[DNAunion]

The only way someone can gain weight while working out without eating or drinking something is through a miracle.



It could occur quite naturally.

Consider someone in orbit about to return to the surface. He weighs himself - 0 lbs - then starts down. On the way down, he does a few curls or what have you. As soon as he lands, he weighs himself again - 155 lbs. This person has gained a whopping 155 lbs of weight while exercising without eating or drinking anything.

All of our explanations that show that a person can't gain 2 lbs while exercising and not consuming any food or liquids have explicitly or implicitly assumed that g (the acceleration due to gravity) remains constant throughout (which need not be true in a generalized case), and that the conservation laws hold.

[Dhaeron]

I don't know: that figure seems awfully high. Did we take into account the incomplete emptying of the lungs on exhalation?
Also, 25l is a bit on the high side, so i'd expect even more as result of an exact calculation.

[dirtymatt]

It could occur quite naturally.

Consider someone in orbit about to return to the surface. He weighs himself - 0 lbs - then starts down. On the way down, he does a few curls or what have you. As soon as he lands, he weighs himself again - 155 lbs. This person has gained a whopping 155 lbs of weight while exercising without eating or drinking anything.

I'll have to check, but I'm pretty certain that her gym does not enter orbit on a regular basis.
:Cheeky:

[DNAunion]

I'll have to check, but I'm pretty certain that her gym does not enter orbit on a regular basis.
:Cheeky:

Some gyms do. And, in case you didn’t notice, the numerous responses in this thread did not use any characteristics – such as lung volume, heart rate, etc. - for the actual people who were exercising in the OP. Everyone generalized the argument.

So not one person addressed the actual peoples' physiology or the actual gyms: it was all generalized.

Second, in case you didn't notice, I was responding specifically to the following statement, not the OP itself:

Vinnie: The only way someone can gain weight while working out without eating or drinking something is through a miracle.

That is a general statement: a very general statement. In fact, it says THE ONLY WAY to do X is Y, which indicates there is no other possible way, at all. I showed that there is in fact a different way.

Further, I explicitly stated:

DNAunion: All of our explanations that show that a person can't gain 2 lbs while exercising and not consuming any food or liquids have explicitly or implicitly assumed that g (the acceleration due to gravity) remains constant throughout (which need not be true in a generalized case), and that the conservation laws hold.

[Agemegos]

Also, 25l is a bit on the high side, so i'd expect even more as result of an exact calculation.

One mole of gas occupies 24.5 litres at SLTP, 22.4 l at STP. But exhaled breath is notoriously warmer than 20 C. By Charles' Law 1 mole of gas at 37 C should occupy 310/293 * 24.5l = 25.9 l. I think 25 litres was close enough for the back of an envelope.

The thing that has me worried is that I seem to have people exhaling carbon that masses more than the dry weight of what they eat in a day. I think the discrepancy must lie in the fact that the lungs are very far from being emptied entirely in a breath of normal respiration.

But anyway, I think the point is made that, counterintuitive though it seems, people can lose significant weight by breathing.

[Matt the Medic]

One mole of gas occupies 24.5 litres at SLTP, 22.4 l at STP. But exhaled breath is notoriously warmer than 20 C. By Charles' Law 1 mole of gas at 37 C should occupy 310/293 * 24.5l = 25.9 l. I think 25 litres was close enough for the back of an envelope.

The thing that has me worried is that I seem to have people exhaling carbon that masses more than the dry weight of what they eat in a day. I think the discrepancy must lie in the fact that the lungs are very far from being emptied entirely in a breath of normal respiration.

But anyway, I think the point is made that, counterintuitive though it seems, people can lose significant weight by breathing.

I've come across some important numbers in my nursing textbooks. Tidal capacity is usually around 500mL in a typical adult at rest, far shy of the total lung volume I reported earlier. This alters the results significantly. Let's try it with 500mL as her tidal volume. (Here, I slap my head for not putting 2+2 together. I work with patients on vents on daily basis, and the tidal volume is typically set at or below 500mL)

4% of 500 is only 20mL

20mL of CO2 per breath, RR 18 (I raised this to a more common average),
18RR*60min*24HR*20mL= 518.4L CO2/24 HRS

518.4L C02 / 25LPM = ~21mol/day
Which is about 250mg (0.252g) of CO2 a day.
Or about 1/2 a pound.

Which is much more accurate. This is of course considering all other variables neutralized (no exertion in breathing throughout the day, gravitational forces (for DNAU) :p, height, etc.)

[Duck!]

Consider someone in orbit about to return to the surface. He weighs himself - 0 lbs - then starts down. On the way down, he does a few curls or what have you. As soon as he lands, he weighs himself again - 155 lbs. This person has gained a whopping 155 lbs of weight while exercising without eating or drinking anything.It's pretty obvious that the OP meant weight in the sense of mass, not in the sense of the gravitational force acting on you.


Duck!

[Norseman]

yes, you can gain weight if you're doing a power-lifting type deal, and not cardiovascular. you're converting calories to muscle. muscle is more dense than fat, and weighs more. if you're running, you're burning more calories but not adding as much muscle. if you're lifting, you're ripping and rebuilding a lot of muscle.

problem is, this is very unlikely. the odds of someone gaining enough muscle mass relative to fat lost to gain weight is highly improbable. in a rigorous workout routine, a person will gain only about 4 kg of muscle.

-Pf

You will gain density like that, not weight. Gaining wieght without having nay extra material added to you violates the laws of physics. Mass cannot come from nowhere, and no mater how much you change mass, you cannot change it so that it gains mass.

[Bumble Bee Tuna]

The laws of thermodynamics are very key here. Do you not think that bioenergetics applies to exercise?

The point is that it doesn't matter what's happening with your energy. Even if your ATP is converted to heat and released, that won't change your mass any. So talking about thermodynamics and things like entropy is really irrelevant.

And consider this. If we discard the laws of thermodynamics, there's nothing to prevent several pounds of mass-energy from just popping into existence inside the person and increasing his/her weight. Everyone here is implicitly relying on the conservation of mass-energy in their explanations.

Well, yes, but I think a lot of people don't count conservation of mass as a law of thermodynamics even though mass = energy so it is in a sense the first law.

Yes it would. If someone added energy to your body, that additional energy would increase your body's mass. It could not be otherwise. And any energy you lose as heat during exercise does decrease your mass.

No, it wouldn't. It would increase your net amount of mass-energy. Your mass would stay the same. Mass and energy are two sides of the same coin, but they are still different. You have a specific amount of mass and a specific amount of energy, and they are measured and considered separately.

if you weigh yourself, and then you warm yourself up, you don't suddenly weigh more. Your mass stays exactly the same. Your energy increases, not your mass.


"E=mc^2 going on" occurs in all kinds of everyday phenonema. Take a bunji cord and stretch it: by your storing potential energy in it you've increased its mass, even though you've not added any atoms. Or take a coal-burning plant: the same amount of mass is converted into energy as occurs in a nuclear power plant for the same yield.

Or more to the point, take chemical reactions that occur in cells. Neither atoms, nor electrons, nor protons, nor neutrons are created or destroyed, yet mass is definitely converted into energy. It's the rearrangement of chemical bonds, which results in changes in binding energy. And if you could measure the mass of the products and the mass of the rectants - using an unbelievably precise scale - for an exergonic reaction, you would find that the products have less mass than the reactants: the missing mass has been converted into energy.

No, you wouldn't. Chemical reactions are just mass being rearranged, not actually converted into energy. Stretching a bungie cord does not add to its mass. Burning coal does not decrease its mass, if you could capture all the gaseous byproducts and release only the heat.

Now, perhaps you mean the degree of mass-to-energy conversion isn't significant enough to bother with in regards to this discussion about weight. That may be so, but then again, what IS significant enough to account for an actual 2-lb gain in body weight if the person doesn't eat or drink, but exercises? Nothing (assuming g, the acceleration due to gravity, remains constant throughout - as we would expect). For example, the matter balance you and others have been discussing: what is the net effect of all of the matter exchanges? How many pounds? How many ounces? Hoe many grams? It's quite negligible.

Very true. if what you were saying were true, due to E=mc^2 there wouldn't even be a measurable change from a year of exercise. However, it's even better than that- not only do you not gain .0000000000000000000000000000000000000001 ounces, you gain 0 ounces. Exactly zero, because energy changes don't affect mass whatsoever in basic chemical reactions.

-B

[llanitedave]

Only if you drink a pound of water.

There's nothing speical about food, it behaves like any other matter. The energy you get from it comes from its chemical bonds. You gain weight when your body takes sugars and fats and converts them into adipose tissue. Or you can build muscle from proteins you eat. (And yes, for all you pedants, you'll build lots of other stuff as you're growing.) But no matter what, you can't gain more wieght than what you eat. Muscle and fat doesn't materialize out of thin air, it must be built from the food you eat. Water will be used for hydrolysis in some cases (as with fat or protein), but again, it doesn't come from nowhere, you have to swallow it.

theyeti

Thing is, if you eat a pound of lard, you darn well BETTER drink a lot of water!

[Plognark]

A co-worker and myself are having an argument with several other co-workers about if it is possible to gain weight after exercising, assuming you do not drink or eat anything while exercising. Ie, you go to the gym, weigh yourself, work out, and weigh yourself again and you have gained two pounds. They both swear it is possible due to either retaining water, or undigested food gets converted to energy or fat. I say that this is not possible. Sure, you can retain water, but if you're not drinking, any water that ends up in your body, had to start in your body. I also don't see how a 1 pound cheese burger can some how become 1.5 pounds of fat.

I can see plenty of ways you can lose weight, sweating, moisture loss from respiration, conversion of stored chemical energy into kinetic energy. I wouldn't expect any of these to acount for a lot of weight loss, sweating being the most.

The only thing I can think of that would cause weight gain would be increased oxygen stored in muscle tissue, but I doubt that could account for a two pound gain.

Am I completely wrong here?

Thanks

I haven't bothered to really read through all of the responses, but yes, you're correct.

keep in mind, bathroom scales or gym scales aren't the most accurate, sensitive measuring devices on the planet. Hell, my scale at home, if I lean one way just a bit, I lose two pounds :rolleyes:

[liquid]

Bumblebee, DNAUnion...

Bumblebee, thanks for answering some of the points DNAU made regarding my comments. However, I think your reply slightly missed the mark...

DNA is actually right in stating that adding energy to a substance can increase its mass. This even happens when you heat a kettle of water, it doesn't require a nuclear fission/fusion process. Can't remember equations off the top of my head mind, but I've had a look at that sort of problem before. So it's not correct to say that thermodynamics is irrelevant on the basis that it doesn't happen, because it does. But when I made my earlier points I was perfectly aware of it.

That, DNA, is why I stated I doubt there's too much E=mc^2 going on, with the too much being a pretty important part of that sentence! Although you seemed to catch onto that halfway through your post, without erasing the stuff previously (but that's useful for people who won't have much idea what we are going on about I suppose).

Sooooo the first part of DNA's longer reply isn't really relevant, because it's the second path, that such effects are negligibly small, that is the key issue.

Just to answer some of your specific points DNA....

Law of conservation of mass is a perfectly recognised term/concept. Google it and you will find over 3mn references, including several universities and NASA on the first page alone. Laws are nothing more than mathematical descriptions, not fundamental theories, and so certain laws that are valid in certain regimes are not in others. Hooke's law is a simple point in case, conservation of mass is another - I use it on a regular basis for fluid mechanics work and so do my various textbooks.

Of course there's an implicit assumption that energy effects are negligible. I have to problem with recognising that, you are correct on that point, and I made it half explicit with my 'too much' comment. But on that point I really just have to say so what? That assumption is

a) effectively true to all practical intents and purposes
b) self-evident to anyone with sufficient knowledge to even think about energy effects
c) very useful in the solution of this problem

and therefore has all the points that makes it a reasonable assumption.

The energy-mass interchanges are so insignificantly small that it's as valid to use as any more refined model. After all, all models are approximations with implicit assumptions, even the most refined ones we could possible conceive of! For the record I also assumed the magical sky-fairy didn't interfere, or (only slightly!) more seriously that we didn't get quantum effects randomly popping matter into the body. ;) Can't list them all.

what IS significant enough to account for an actual 2-lb gain in body weight if the person doesn't eat or drink, but exercises? Nothing

yes, I know dust etc. flows are insignificant. That was exactly the point in fact, that there were no significant mass inflows. If you read back carefully, I wasn't trying to justify the claim, but debunk it.

So in summary, I don't disagree with any of your physics in the slightest, but I think you are being over the top with making assumptions explicit. However, because I was dismissive of thermodynamic effects without indicating why, and you had already referred to it, I can understand why you'd want to defend your post, in which case fair enough.

But with clarification, I stand by my assumption as a a reasonable one, and I don't think you should disagree with that - sometimes making reasonable assumptions is the right thing to do! But that's a philosophy of science debate, and we are just here to solve a practical problem, and we do of course agree that it's not possible.

As for bleeding, ever played rugby?! :D

[DNAunion]

The point is that it doesn't matter what's happening with your energy. Even if your ATP is converted to heat and released, that won't change your mass any.

Sorry, but it would change your mass.

Bumble Bee Tuna: So talking about thermodynamics and things like entropy is really irrelevant.

As I said before, throw away the first law of thermodynamics/the law of conservation of mass-energy and then one can no longer say that a person can't gain 2 lbs when exercising if he didn't eat or drink anything ... and g remains constant, of course :-) Shoot, 20 pounds of mass-energy could just spontaneously pop into existence within the person.

And the second law makes it clear that during exercise, during which energy transformations are occuring, you can't even break even in regards to mass-energy: your 'burning calories' will directly cause a reduction in your mass as some of the chemical energy is converted into a less usable form - heat - which escapes from the body. If were threw out the second law, and allowed for 100% efficient transformations of energy, then one could exercise indefinitely without having to eat or drink because he could just continue to recycle the starting amount of energy over and over again.


Bumble Bee Tuan: No, it wouldn't. It would increase your net amount of mass-energy. Your mass would stay the same. Mass and energy are two sides of the same coin, but they are still different. You have a specific amount of mass and a specific amount of energy, and they are measured and considered separately.

Not so. If you had a percise enough scale, you could see that increasing the internal energy of a system increases its mass, even though it doesn't add any atoms. But I'll address this in a minute, where you repeat your error.

Bumble Bee Tuna: No, you wouldn't. Chemical reactions are just mass being rearranged, not actually converted into energy. Stretching a bungie cord does not add to its mass.

Wrong.

By the way, the reason I picked the bunji cord example the first time is because I have a video lecture series on physics in which the Ph. D. lecturer -professor Richard Wolfson, from Middlebury College - uses exactly that example to show that E=mc^2 conversions occur even in everyday phenomena.


Bumble Bee Tunay: Burning coal does not decrease its mass, if you could capture all the gaseous byproducts and release only the heat.

Wrong again.

By the way, the reason I also picked the burning coal vs. nuclear reactor example is because of the same video lecture series on physics with professor Richard Wolfson, from Middlebury College. He also uses exactly that example to show that E=mc^2 conversions occur even in everyday phenomena.


Bumble Bee Tuna: if what you were saying were true, due to E=mc^2 there wouldn't even be a measurable change from a year of exercise. However, it's even better than that- not only do you not gain .0000000000000000000000000000000000000001 ounces, you gain 0 ounces. Exactly zero, because energy changes don't affect mass whatsoever in basic chemical reactions.

Wrong again. Mass does change in exergonic chemical reactions: where do you think the liberated energy comes from? Do you think it just poofs into existence? Well, it doesn't. It comes from the "missing" mass.

[DNAunion]

This isn't the actual lecture statements from the physics video lecture series: this is from the accompanying course guidebook.

"Actually, E=mc^2 applies to all energy transformations, including the chemical reactions involved in burning coal or gasoline or metabolizing your food, as well as the nuclear reactions that power the Sun or our nuclear reactors and nuclear weapons. Even a stretched rubber band weighs more than an unstretched one, because of the energy put into stretching it." (emphasis in original, course book for Einstein's Relativity and the Quantum Revolution, Part 1, Professor Richard Wolfson, The Teaching Company, p53)

[Bumble Bee Tuna]

wow, I stand corrected, I think? I have no idea how I never could have learned this.

[Boro Nut]

wow, I stand corrected, I think? I have no idea how I never could have learned this.

Never say never. I'm sure you could learn it if you really tried to.

Boro Nut

[DNAunion]

Law of conservation of mass is a perfectly recognised term/concept.

Yeah, I had it all backwards: my bad. It IS the law of conservation of mass, NOT the conservation of matter. I have a hard time keeping that straight because it's a misnomer. In chemical reactions, matter (as in the number of atoms and other particles) remains constant ... but mass changes. So matter is conserved while mass is not, yet it is called the law of conservation of mass.


liquid: The energy-mass interchanges are so insignificantly small ...

Are they that small? A pound of body fat is equal to about 4200 Calories of energy (if burned). An average (70kg) man who runs for an hour burns about 1,084 Calories. That amount of energy is equal to approximately a quarter pound of body fat. Not too shabby if you ask me. And where does that energy come from? Wouldn't it be the "missing" mass resulting from the exergonic biochemical reactions?

[theyeti]

Urine typically has <5 mmol / L of CO2. I'm not sure how much else is carbon in other forms, considering nearly every molecule in our body has carbon in some form in it :D.

I dont have any exact sources with me but I recall that in exhalation only ~4% of the air is CO2, but considering that normal lung capacity is somewhere around 4 liters, 4% of that is quite simply 160mL. I don't have to do the conversion to mmol to show that CO2 leaves the body in a far superior quantity via exhalation. :)

Of course carbon and CO2 in stool is an entirely different beast. That has a ton more to do with what you consume and the reactions your food has with your Gi Tract. Many foods such as dairy and medicines such as laxitives actually release CO2 as a byproduct (Gas anyone?)

I was really talking about carbon, not CO2 specifically. Most carbon in urine is probably in the form of urea. Urine is about 5% urea. Carbon makes up about 20% of the mass of urea, so that would be about 1g of carbon for every 100ml of urine, roughly speaking. Since the average person probably excretes at least a liter of urine a day, that would be 10g just from urine. Feces probably contains far more carbon though. I'd still curious as to just how much.

theyeti

[Dhaeron]

Are they that small?
Yes.

A pound of body fat is equal to about 4200 Calories of energy (if burned).
Note that "burned" in this case does not mean that one pound of mass is converted into energy, but rather that all the chemical energy contained within a pound of body fat, and the body can use, is used up. One pound of mass *converted* into energy would yield about 1*10^16 cal. (assuming the metric pound)

An average (70kg) man who runs for an hour burns about 1,084 Calories.
So, about 4*10^-11 g. Irrelevant, isn't it. ;)

That amount of energy is equal to approximately a quarter pound of body fat.
Yes, but equivalent to the chemical energy contained in a quater pound of body fat, not the total energy. Most (virtually all) of the fat will just be converted into other substances.

[Duck!]

Not so. If you had a percise enough scale, you could see that increasing the internal energy of a system increases its mass, even though it doesn't add any atoms. But I'll address this in a minute, where you repeat your error.I realise that increasing the internal energy system will increase because of the mass/energy equivalance, but I don't see in any of your posts where you explain where this extra energy comes from. We've already agreed that the person in question doesn't eat or drink anything.



Duck!

[DNAunion]

DNAunion: Not so. If you had a percise enough scale, you could see that increasing the internal energy of a system increases its mass, even though it doesn't add any atoms.

I realise that increasing the internal energy system will increase because of the mass/energy equivalance, but I don't see in any of your posts where you explain where this extra energy comes from. We've already agreed that the person in question doesn't eat or drink anything.


I think you need to go back and look at the chain of statements leading up to those. The context has been lost and you appear to now have me saying things I didn't.

[DNAunion]

DNAunion: An average (70kg) man who runs for an hour burns about 1,084 Calories.


So, about 4*10^-11 g. Irrelevant, isn't it.


Yes and no.

I agree that I got confused, considering the burning of a pound of fat in one spot as it should be, and thinking about it as being all converted into energy in another; and that that led me to the wrong conclusion - which you pointed out.

But my calculation ends up different than yours: if mine is right, yours is about 1,000x too low.

1 Cal = 1 kCal = 4.184 kJ = 4,184 J

1,084 Cal = 1,084 Cal (4,184 J / 1 Cal) = 4.535 x 10^6 J

E = mc^2
m = E / (c^2)

m = 4.535 x 10^6 J / [(299,792,458 m s^-1)^2]
m = 4.535 x 10^6 J / (8.9876 x 10^16 m^2 s^-2)

1 J = 1 kg m^2 s^-2

4.535 x 10^6 J = 4.535 x 10^6 kg m^2 s^-2 = 4.535 x 10^9 g m^2 s^-2

m = (4.535 x 10^9 g m^2 s^-2) / (8.9876 x 10^16 m^2 s^-2)
m = 0.5046 x 10^-7 g

m = 5.046 x 10^-8 g

Irrelevant for sure, but that would be 1,000x less irrelevant than what you calculated (assuming I didn't blunder in my calculation).