Where does it go?

What happens when you decide to lose weight?

Well, first thing that happens is that you have to start using up more calories than you consume. That, and you keep weighing yourself.

If you're like me, you get confused by some of the things your scale shows you. The patterns just don't seem to make sense.

It helps to know a few of your body's basics, like where does the weight go when you lose fat?

I read an article where a bunch of people were asked that question. One of the most common answers was that the fat was converted into energy, so you weigh less. That's very wrong. Your body is a chemical engine, not a nuclear one. You can't destroy matter, except on a theoretical level. To create all the energy your body uses in a lifetime, it would require the destruction of far less than a single gram of matter. Far, far less.

So where does it go?

Another surprisingly common answer was that you poop it out. Really? Your digestive system is self contained, and is a one-way route INTO your body. Quite a bit doesn't get absorbed, but that has nothing to do with elimination of waste from inside the cells of your body.

That must mean you pee the weight out. In part, yes, but only a small percentage.

Think of your body like a fire. Even the metaphors we use do that; we say we “burn” fat. What happens when fire burns? If you start with ten pounds of wood, you end up with just ounces of ash. Where does the rest of the wood go?

It burns. The carbon in the wood combines with the oxygen in the air, and it flies away.

In your body it's more complex. The formulas for the various components of your fat all look more or less like the one for Linoleic Acid; C18 H32 O2. I don't know if Linoleic Acid is actually fat, but I Googled the formula for fat and got a page of chemistry that all looked just about exactly like it. I just picked a typical one. None had anything other than hydrogen, oxygen, and carbon.

Break the bonds of that apart with lots of oxygen around. The oxygen in the acid just joins the party. The hyrdogen links up with some of that oxygen and turns into water, which will eventually end up leaving the body through the kidneys, or possibly as sweat or some such.

The carbon also links up with oxygen, forming carbon dioxide. How does the body get rid of carbon dioxide? That's right. It leaves through your lungs.

Interestingly, the carbon in the acid molecule makes up 80% of its weight. If you lose 10 pounds of fat, about 20% of it turns into water and 80% into air.

Knowing that makes the silliness of the bathroom scale make a little more sense.