So, this is kind of a two part question. First, I guess I am wondering where the fat goes when you lose it. I am sure there have been previous posts on this, and I've heard that you just metabolize it and (sorry, gross) pee it out, for lack of a better way of phrasing it. Is that true? I ask because I think it's kind of important to to know how all of that works. If there is a previous post discussing this, feel free to link to it.

Secondly, the past few days I have had HUGE losses overnight. Like, between the time I went to bed Tuesday night and the time I woke up Wednesday morning, I lost 1.4 pounds-- from 135 even to 133.6. I did not go to the bathroom or anything between those times. Then it happened again last night-- 133.6 to 132.8. I know that is a pretty big loss for two days, so it is probably water weight, but where in the world is it going? It's not coming out of me physically... Is my body just redistributing the weight? Can the scale even tell? Is my scale just broken? Haha. Seriously, if anyone has any idea, do tell, because I am very curious.

You breathe it out, seriously

http://www.ehow.com/how-does_4926344...se-weight.html

Your body releases heat through your skin, water as you sweat and carbon dioxide as you breathe; it converts the energy in the bonds of ATP into energy your body can use.

That's really cool! Thanks!

Yup. What they said.

Calories are a unit of energy. They fuel a person just like gas fuels a car. Where does gas go when the car uses it? Well... the car burns it up and converts it into all the actions that the car does like spinning the wheels.

So calories are used similarly. The body takes them and uses them to fuel your actions like walking, breathing, jumping, blinking, heat, sweat, beating of the heart, thinking... everything. And fat, which is just a storage chamber for the calories (it's probably more complex than that, but for simplicity sake, let's just say that's it's only function), acts in the same way. It just has to take an extra step from calories and convert the stored energy into usable energy.

I'm glad you asked this question! I've been wondering the same thing... now can anyone explain why I weighed more after 30 minutes of cardio when I hadn't drank any water or anything in between? Not that it bothers me, I'm really more curious from a biological standpoint.

Other than working out in a humid room (where breathing in water/extra water condensing on skin might make some kind of difference), can't think of any reason for this. Scale error? Change of clothes/shoes?

The average scales is not accurate or precise

I don't know the biological reason, but someone told me that you weigh more after exertion. So if you wait 15 min or so after a workout til your body has calmed down you should weigh less again? At least that's what I was told. Don't know how much truth there is to it.

You took in more oxygen. Oxygen has mass.

Seriously, I think it was probably the scale.

I love that someone asked this because I have always wondered exactly this too.

All I can think of is a chemical change inside the body... For example, ice is water, water is steam, but ice is a lot heavier than steam. But I don't really buy my own argument

Muscle weighs more than fat... so perhaps your muscles expand a bit after a workout and get all puffy? Just a guess... (I have a difficult time beliving you can get something (weight) from nothing though... especially when you're using energy. What a mind boggler!)

I think all of the medical advice is good.
But for myself, I like to picture all these fat stores I'm burning off floating up into the air, flying across the world and attaching themselves to some poor starving child in a third-world country. Clearly, i don't need them...why not share!?

About the OT, I always lose around that much from night to morning. I weigh in twice a day, at night right before bed and in the morning right after I've gone to the bathroom. The change is usually anywhere from 1 to 2 pounds. The change from one morning to the next isn't usually that much, though. I gain some during the day, and then it is gone the next morning. Water weight and food and what not. Is it not the same for other people?