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Where does weight go overnight?


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I've always heard matter cannot be created or destroyed... so how is it possible I weigh myself right before I go to bed at night and wake up the next morning and weigh myself again (without using the bathroom or anything) and I have lost 2 lbs?  I'm not complaining but it just seems weird... like, where does it go?   Evaporation?? 

Laughing

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you breath moisture and sweat, it adds up....

Perspiration, that's where is goes.  Yes, you sweat while you sleep.

Also, the carbon dioxide you breath out weighs more than the oxygen you breath in. How neat is that? Here is a diagram.

matter cannot be destroyed, but energy can be converted.  chemical energy from food is converted into heat energy and kinetic energy as the food is digested.  that energy (calories) goes off to convert into other things.  moving, breathing, thinking, dreaming, circulating blood - all those things consume (convert) energy.

while energy itself doesn't have mass, the cells that contain the energy do.  regular bodily functions demand energy, and to get to that energy, the cells of nutrients are consumed.  this happens constantly, whether we're asleep or not, but while we're asleep, we're not replacing those nutrients.

either that or i'm just making up ****.

I thought about sweat and stuff, but 2 lbs is like... 4 cups!!  My bed would be soaked!  Kinetic energy, though, that sounds good.  :)

Original Post by pgeorgian:

matter cannot be destroyed, but energy can be converted.  chemical energy from food is converted into heat energy and kinetic energy as the food is digested.  that energy (calories) goes off to convert into other things.  moving, breathing, thinking, dreaming, circulating blood - all those things consume (convert) energy.

while energy itself doesn't have mass, the cells that contain the energy do.  regular bodily functions demand energy, and to get to that energy, the cells of nutrients are consumed.  this happens constantly, whether we're asleep or not, but while we're asleep, we're not replacing those nutrients.

either that or i'm just making up ****.

I'll go with just making it up.  Smile  Cells cannot be turned into energy - nor can nutrients.  At least, not in the way you've implied.  The only time mass and energy can be interconverted is in nuclear reactions, and I'm really hoping you're not radioactive!

Your body breaks nutrients down into smaller pieces - eventually into water and carbon dioxide.  You exhale both.  (Yes, you sweat a little, but I sure don't produce two pounds of sweat overnight!)

#7  
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Original Post by adolphs:

I thought about sweat and stuff, but 2 lbs is like... 4 cups!!  My bed would be soaked!  Kinetic energy, though, that sounds good.  :)

bmfan77 is right, your breath has a high moisture content.  Remember breathing on glass and writing in it. 

As a backpacker I can tell you that a poorly vented tent, with a ground tarp, will be soaked on the inside from nothing more than your breath in the morning.

Original Post by susiecue:

Original Post by pgeorgian:

matter cannot be destroyed, but energy can be converted.  chemical energy from food is converted into heat energy and kinetic energy as the food is digested.  that energy (calories) goes off to convert into other things.  moving, breathing, thinking, dreaming, circulating blood - all those things consume (convert) energy.

while energy itself doesn't have mass, the cells that contain the energy do.  regular bodily functions demand energy, and to get to that energy, the cells of nutrients are consumed.  this happens constantly, whether we're asleep or not, but while we're asleep, we're not replacing those nutrients.

either that or i'm just making up ****.

I'll go with just making it up.  Smile  Cells cannot be turned into energy - nor can nutrients.  At least, not in the way you've implied.  The only time mass and energy can be interconverted is in nuclear reactions, and I'm really hoping you're not radioactive!

Your body breaks nutrients down into smaller pieces - eventually into water and carbon dioxide.  You exhale both.  (Yes, you sweat a little, but I sure don't produce two pounds of sweat overnight!)

okay, look, susie.  my understanding of biochemistry is minimal at best, but the "exhalation and sweat" explanation completely ignores metabolism.  food is made up of cells, yes?  like everything else.  and we need the energy from food to live, yes?  and energy can be converted, but not destroyed, yes?

yes, we exhale, and yes, we sweat, and yes, we pooh and pee.  but we also convert food energy into heat and kinetic energy.  and once we've done that, those energy forms are no longer ours to claim.  they go off to heat and move other things.  and the sources that provided that energy for us (food, fat stores, muscle) are depleted.

no?

and we do that 24 hours a day.

and i really need a massive wee in the morniing even if i had one before bed.. .and i def didn't have a drink in the middle of the night when i was asleep!

 

I think the answer is much more simple than what people are saying. Food and water weighs quite a bit in your stomach. Drink 2 glasses of water and you may find you gained a pound from it! Only initially of course until it's distributed in your body, etc. So all night for 7ish hours you haven't eaten or drank anything. So there's nothing in your stomach to add weight. So before bed your weight might include some of what you had for supper or a snack, as well as any drink, etc. By morning it's no longer sitting in your stomach. Well I guess it's still kinda with you until you go to the bathroom, but still. Makes sense to me. Have you ever weighed yourself after you ate? You'd be amazed.

Original Post by pgeorgian:

okay, look, susie.  my understanding of biochemistry is minimal at best, but the "exhalation and sweat" explanation completely ignores metabolism.  food is made up of cells, yes?  like everything else.  and we need the energy from food to live, yes?  and energy can be converted, but not destroyed, yes?

yes, we exhale, and yes, we sweat, and yes, we pooh and pee.  but we also convert food energy into heat and kinetic energy.  and once we've done that, those energy forms are no longer ours to claim.  they go off to heat and move other things.  and the sources that provided that energy for us (food, fat stores, muscle) are depleted.

no?

and we do that 24 hours a day.

I second this. If you weren't converting 'energy' (read: calories, read: food), into heat, then you're temperature would be... zero. Cars are inefficient, because they lose so much energy to heat, when you're body is maintaining it's temperature, it's doing so with calories. Oh, and it's making your heartbeat, and your lungs work. And thinking uses calories (ever wonder why you're tired after a long hard test?), so I assume dreaming does also. Why? because all those pesky firing nuerons need energy. And where does energy come from? Calories. And where do calories come from? food. So you're body is using food (as in converting it), into usuable forms of energy, such as kinetic and heat, and when you 'burn' something, you use it's mass/weight.

Original Post by theholla:

Also, the carbon dioxide you breath out weighs more than the oxygen you breath in. How neat is that? Here is a diagram.

 love this link! i am the paragon of animals! i am a... a...water pump. heh.

this is why it best to weigh in the morning, because you have the least amount of water in your system.

this also explains why if you have one of the percent body fat calculator scales you want to do that in the evening - because its more accurate if you are hydrated.

awesome! i love it when i search the web and the most concise answer is from here!

Energy and mass are not the same thing. 

When you burn firewood you do not convert the "weight" of the wood into heat. 

Your body is throwing off moisture all night, a sweat so light that it evaporates before it soaks the sheets and most through breathing. 

Original Post by pgeorgian:

okay, look, susie.  my understanding of biochemistry is minimal at best, but the "exhalation and sweat" explanation completely ignores metabolism.  food is made up of cells, yes?  like everything else.  and we need the energy from food to live, yes?  and energy can be converted, but not destroyed, yes?

yes, we exhale, and yes, we sweat, and yes, we pooh and pee.  but we also convert food energy into heat and kinetic energy.  and once we've done that, those energy forms are no longer ours to claim.  they go off to heat and move other things.  and the sources that provided that energy for us (food, fat stores, muscle) are depleted.

no?

and we do that 24 hours a day.

Yes, there is energy transfer.  But the energy is not coming from the cells in the way that you're suggesting.  The energy is released by bonding together atoms (not by breaking bonds as is commonly but incorrectly suggested on sci fi shows/movies).

For the sake of argument, I'll focus on sugar, but the same type of thing happens to other foods too.  Enzymes break the sugar down into smaller pieces - water and carbon dioxide.  The bonds in a water or CO2 molecule are stronger than the bonds in the sugar molecule were, so these molecules are lower in energy (science speak for 'more stable'/'happier').  Since energy can neither be created nor destroyed, the difference in energy is released for our bodies to use. 

It's like in a campfire.  The larger cellulose molecules in the wood break down into smaller, more strongly bonded molecules of water and CO2 and energy is released.  And when the campfire is done burning, the mass of wood/ash left is a lot less than you started with because most of the atoms left as water/CO2 evaporated.

I hope that makes some sort of sense.  These things are much harder to explain when you can't draw pictures.  I like pictures, darnit!

The mass of the campfire ash is indeed less, but ,as susiecue noted, no mass disappeared.  The making of the heat is a chemical reaction, so the body making heat does not eliminate mass.  The mass that goes in is the amount that comes out.  Unless you have kissing bugs around the weight lost while sleeping is moisture.  When its cold and you see your breath fog up, that is moisture not heat, but hot air can hold more moisture so it is visible in contrast.  Multiply the amount of moisture you see in your breath on a cold day times the number of times you exhale in a given night and it adds up very quickly.

thhq
Jul 18 2009 22:50
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#16  
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This sounds about typical for nighttime weight loss.

The loss is due to metabolism.  In 12 hours without eating the average person burns about 800 calories.  As pure carbs or protein this is about 200 grams dry weight.  But that weight is associated with liquid.  The foods we eat are around 10-20% solids.  So the total food weight to supply 800 calories is more like 1300 grams, or 3 pounds.  The weight is lost as water mostly (through the kidneys as urine, through respiration and through perspiration), but also as carbon dioxide by respiration.  Some of it - maybe a third - stays in your lower intestines.

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