Why do you weigh less after sleeping?

[chp03bcd]

You also wake up taller than you were the night before

[Supra-Brett]

Put a small mirror in the fridge then when its nice and cold take it out and breath on it. the water vapour in your breath will condense on the cold surface.

 

This water weighs a small amount.

 

Multiple that small amount by the number of breaths you take in a night and the water loss through breathing adds up.

 

Add this water loss through breathing to fluid and salt loss through sweating and hey presto you have accounted for the weight loss.

 

Remember that matter can neither be created nor destroyed so the weight must be going somewhere.

 

The water/sweat examples above are a suitable hypothesis to account for the weight loss.

[Carl_S]

As you sleep your dreams lift away waste material (day residue) from your mind, this goes away into nothingness. The weight associated with this is why you way less in the morning, since you have gotten rid of some your excess weight.

[RedM]

As you sleep your dreams lift away waste material (day residue) from your mind, this goes away into nothingness. The weight associated with this is why you way less in the morning, since you have gotten rid of some your excess weight.

 

Don't plagiarise my posts. Oh, and spell weigh correctly next time too, you big faker.

[Carl_S]

Deep breaths.

 

Life is an adventure.

[DJButler]

Don't plagiarise my posts. Oh, and spell weigh correctly next time too, you big faker.

 

Plagiarism is the sincerest form of flattery!!!!!!!!!!!!!!

 

P.S I stole that from someone else.

[jevansio]

Don't plagiarise my posts. Oh, and spell weigh correctly next time too, you big faker.

I agreee, I thought your response was one of the whittiest replys on here in ages (bar LBM's posts)

[TonyP]

As you sleep your dreams lift away waste material (day residue) from your mind, this goes away into nothingness. The weight associated with this is why you way less in the morning, since you have gotten rid of some your excess weight.

 

Twat

[Lbm]

Twat

 

 

 

Cat.

 

 

 

 

Sorry, thought this was mallet's mallet.

 

 

I didn't really.

[TonyP]

Cat.

 

 

 

 

Sorry, thought this was mallet's mallet.

 

 

I didn't really.

 

Post whore.

[Lbm]

Post whore.

 

Why yes?!

 

Now enough of this hijackery...

[stevie_b]

*waits for someone to pull the plane/conveyor card*

 

I agree with you there Steve, but Ralphman is asking why you weigh less when you wake up after you go to sleep, i.e no mass is being introduced to the system.

In answer to the OP's question, you weigh less after sleeping because you sweat and lose water via breathing. No weight loss is due to muscles working.

 

If you look at your basic metabolic rate http://www.bmi-calculator.net/bmr-calculator/ and put in height/weight it'll give you calories you'd roughly use without doing any exercise.

You'd burn calories, but you wouldn't lose any weight at all (assuming no sweating etc).

 

I agree with your about chemical energy, but petrol still has mass! Body-fat is mass, it's burnt off whilst you're asleep or awake, if your body does not have any other chemical/mass in the tank otherwise. Surely body fat is part of your overall mass? Yes it goes through a process to be used and converted into kinetic/heat energy, I agree no energy can be created or destroyed, just converted.

Body-fat does have mass, but the mass isn't burnt off. For example, 1kg of food will give rise to 1kg of cr@p+pee, if the body decides not to store it as fat. If it does store it as fat, then you gain weight by virtue of not expelling everything you've eaten.

 

Suppose I was a strange chap (even stranger than I already am ) who didn't sweat, exhale moisture or lose dead skin. If I went for a run, I wouldn't weigh any less than when I started. The only way I could lose weight is by going to the toilet.

 

Same goes for a car engine. 1kg of petrol+air, when burned, will produce 1kg of exhaust gases. Like energy, mass is neither created nor destroyed.

[Scott]

So does the plane take off?

[Tannhauser]

 

 

In answer to the OP's question, you weigh less after sleeping because you sweat and lose water via breathing. No weight loss is due to muscles working.

 

That's not strictly true, because there is a connection between 'muscles working' and weight lost through breathing.

 

The energy required to maintain life processes, for movement and to generate heat comes from the oxidation of molecules derived from food. This oxidation results in the production of waste product molecules, principally water and carbon dioxide.

 

What you're missing is that most of that carbon dioxide, and a proportion of the water, is removed from the body during exhalation.

 

Using some dodgy assumptions and back of the envelope calculations,we could have a bash at how much mass is lost through the respiration of food.

 

Let's say a smallish bloke burns 80 calories an hour during sleep (probably not too far out), and sleeps for eight hours. That's 640 kCal. If we also assume that he respires either carbs or protein to produce that 640 kCal, well both of those produce about 4 kCal per gram, so he's converted about 160g.

 

OK, now assuming those carbs/protein are converted to glucose as they enter the aerobic respiration reactions, we can work out how much CO2 and water are produced.

 

The summary equation is (apologies for no subscripts):

 

C6H12O6 + 6O2 -> 6H2O + 6CO2

 

The molecular weight of water is 18 and CO2's is 44. Therefore, 1g of glucose produces 18/62 g of water and 44/62 g of CO2.

 

160g would produce 46g of water and 113g of CO2. He's going to lose most of that CO2 through breathing out. I've been puzzling over the water part for a while. The water that is produced by aerobic respiration (the reaction, not the breathing process) will go into the bloodstream, and it's the kidneys that mainly regulate that. Water is lost through breathing, I think, as a result of differential partial pressures and diffusion. I doubt that burning more calories makes you lose more directly because of the extra water produced.

 

Anyway, the summary: you do lose a small amount of weight from breathing out CO2, which is directly linked to metabolic rate, which in turn is directly linked to muscular activity. Water loss from the lungs derived from metabolising food is probably minimal. However, loss from the lungs is more substantial because of natural diffusion. My guess is that the vast majority of water is lost through sweating.

[Tannhauser]

Curses, I've just realised that I haven't taken account of the mass of oxygen taken in for aerobic respiration, which messes up my calculations. There's still a net loss in weight through the lungs from expiration of CO2, but it's even less than I thought initially. I'm too tired to work out how much.

[Rob]

That weight you lose during sleep is in fact the weight of the world. It's usually found on your back but when you sleep and forget about all your worries the weight of the world is lifted.

 

If you took that 3/4lb and multiplied it by the number of people on Earth it would actually be the same as the physical weight of the planet.

 

That's not scientifically provable but it is a fact.

 

Are crabs paedophiles?

[Carl_S]

I don't pretend to understand the above formulae, but this is why weight training (working out in the weights section of the gym for example) can help you lose body weight overall.

 

I have read that it can be even more effective than cardiovascular workouts alone.

[stevie_b]

Hmm, good posts Tannhauser! I'm enjoying this. I'll have a think and get back to you.

[Tannhauser]

Double post

[Tannhauser]

 

Suppose I was a strange chap (even stranger than I already am ) who didn't sweat, exhale moisture or lose dead skin. If I went for a run, I wouldn't weigh any less than when I started. The only way I could lose weight is by going to the toilet.

 

Same goes for a car engine. 1kg of petrol+air, when burned, will produce 1kg of exhaust gases. Like energy, mass is neither created nor destroyed.

 

Just looking back at this post, the idea of mass conservation and energy conservation are spot on. If you were to get someone to sleep in a huge sealed plastic bubble, there would be no net change in weight of the bubble, as the sleeper would merely have converted one lot of mass (carbs, fats, protein) into another (CO2, water, urea). Likewise, if no energy can escape the bubble in any form, there's no net change. The bond-energy that was holding the food molecules together has been converted into other forms, principally heat.

 

However,as Mr.Caseys points out, the body itself is not a closed system and some of this converted mass is lost.

 

Going back to the respiration equation, I reckoned a night's sleep uses the equivalent of 160g of glucose. To make the maths easier, if we up that to about 180g, we get this:

 

180g glucose + 192g of oxygen* breathed in -> 264g of CO2 breathed out + 108g of water, either breathed out, sweated out or removed by the kidneys to be later peed out.

 

Even if we say that he isn't losing any of the water produced by respiration (he stores that in his bladder until morning), he still has to release CO2, or he will die. The mass of CO2 minus the mass of oxygen taken in is (264 - 192)g, or 72g. This represents the mass of the carbon that's been 'removed' from the glucose molecule.

 

If someone loses about a kilo overnight, then if these calculations are on the right lines, very little of it is due to "burning food" (a misleading phrase) - the vast majority is probably from sweating and water lost through breathing out, which doesn't derive from aerobic respiration of food.

 

*180g = one mole of glucose. This requires six moles of O2, which weighs 6 X (16 X 2) = 196g. Six moles of CO2 are produced, which weighs 6 X (12 + (16 X 2)) = 264g.

[Ewen]

I remember a dedicated Kirby salesman years back...one of the demonstrations he gave us was Kirbying our mattress, after installing a clean bag....my wife was horrified at the amount of light grey muck the Kirby produced after just one sweep of the mattress. Dead skin and mites according to said Kirby salesman.

I let him keep it as a visual aid for use on future customers.

My wife made me buy a new mattress soon after, and I must have bought a good one as it lasted nigh on twenty years.

[Kirk]

christ, my BMR is 1715.31 sheesh no wonder i struggle to put weight on! the advantages of being young

[Pete]

Perhaps you don't lose weight whilst asleep, but you're putting it on during the day.

 

Interestingly I saw a program the other day whereby a chap doing exercise (just walking at a pace) he used X many calories...but then carried on "burning" calories throughout the night.

They did the experiment with and without the exercise measuring him throughout the night and the difference was quite significant.

[Chris Wilson]

Define night. I go to the pub after darkness falls, wake up well after first light, and invariably I am heavier, although financially lighter, what's the bloody secret then?

[stevie_b]

However,as Mr.Caseys points out, the body itself is not a closed system and some of this converted mass is lost.

 

Tannhauser and caseys, I think you've spotted a flaw in my argument here. I was trying to approximate the body as a closed system by including the sweat and breath-moisture in my sums. But it isn't as simple as that, because the body is taking on mass every time it inhales and pushes it out every time it exhales. I was assuming that the air that is breathed could be cancelled on both sides (inhale and exhale), but of course that doesn't work: for inert gases such as nitrogen this is OK (nitrogen is sucked into the lungs, and I presume expelled straight back out again), but inhaled oxygen chemically combines with compounds already in the body, and then exhaled as a different compound, thus potentially giving a weight loss.