This is not an article about weight loss. It’s an article about how our bodies shed weight.
One day I might want to write an article about weight loss and our cultural obsession with losing weight, but really, we know how it works pretty well – eat less than what your body burns. Loads of veggies, nuts and fruits will be your best bet. If your goal is to lose weight, I won’t lie, it won’t be easy – and if you want it to stick it won’t be quick either. But it will work. Spending a lot of money on magic powders and potions might help, but in the end they all work by making you take in less energy than you spend. Crash dieting and crazy exercise feats just make it more likely you’ll gain weight again, and maybe more than you had to start with (see How The Biggest Loser participants all put their way back for an A+ case study). Anyway, as I said, not why we’re here.

So, when one loses weight, where doth it go? If you told someone you lost weight and they asked you “Where did you last see it?”, what would you answer? Does our body stash it away in the closet for a rainy day? Or does it become tears as we eat a whole cake after having a breakdown from the latest intermittent fast attempt?
Is it poop or wees?
No, it’s not.
Although a typical feces session weights about 0.5kg (give or take depending on the person’s size), most of what comes out is bacteria, protein, fiber, some salt and some fat (mostly from the food you ate, not from what’s in your body) and something experts very non-vaguely define as “waste material”. With our pee, most of it (roughly 96%) is water and the rest is salts and acids from things our body doesn’t want anymore (aka waste material).

A lot of what makes up that “waste material” is dead blood cells. Our blood cells only live about 120 days and when they go, our body takes out the iron to make new ones, and lets the liver deal with the remains of each cell (called urobilinogen). Once in the digestive system, some of them will be processed by bacteria in the intestine, giving them a brown-ish colour in the process. Some others will go back into the blood stream, at which point your friendly kidneys will pick it up to pass on to the bladder, which renders it yellow. (If you need visuals, this is an excellent watch.) You do lose some weight from this process, in the scale of milligrams per poo/wee. But your body is constantly making new blood cells from the food you ate and the iron it stored, so ends up pretty much same same.
Something interesting for you to ponder: people sometimes find themselves lost, in deserts or isolated islands and such, and go for long times without eating or drinking, which means they stop pooping and peeing, but they still lose a lot of weight. So, riddle me that Sherlock.
Oh, I see, it’s sweat then

Great logic, but no. Sweat is mostly water that your body pumps out in a desperate attempt to cool itself down. Granted you lose some water, but drink a glass of it and a bit of salt (waste material) and you gain that weight again.
If you want lose weight to “look sexy”, there’s an area where sweating can help though. Some sweating, specially the kind from armpits and groin, are a sure way to signal to a potential mate that you have the hots for them. Helpful bacteria get in the way, consume some of that sweat and “enhance” your natural scent, making you even more attractive. Industrious little creatures. And some people say romance is dead. But I digress.
Some weight, just a little tiny bit, goes out through “waste” and sweat, but it won’t account for most of the weight you lose when eating in caloric deficit. So, if our body is not furiously pumping out the extra fat through your intestines, bladder or sweat glands, how in the name of the heavens do we lose weight?
What Phil meant by “it” when he talks about what he felt that night
Here’s a very interesting experiment for you to do on yourself. After your last bathroom break before bed, weight yourself, write it down. Then, in the morning when you wake up, first thing before anything, weigh yourself again. I promise, provided you didn’t have any midnight snacks, 100% money back guarantee, you will have lost at least 100 grams. Now do that for 10 days and you’ll lose 1kg. Repeat the strategy until you lost those “just 5 little kilos”. You’re welcome.
If you’re like me, you probably did not do a whole ton of exercise during the night. The only thing you did is pump blood around, breathe and dream about rollercoasters that turn into fluffy bunnies and end up dropping into a pool full of cabbage patch dolls.

If you didn’t sweat too much, the only thing that came out of your body was air. Yes. Good old air. And with it, many grams of something that once was fat.
For something that doesn’t feel like it weighs a lot, it’s almost magic that losing weight would happen by exhaling the by-product of your body using energy. But it does. It’s a scientific fact that 1 kilo of air weighs 1 kilo and all scientists agree with me on that one.
You see, our cells need a few main chemical bits to get the energy they needs – carbs, fat or protein, water and oxygen. Once those get into the cell witchcraft happens, they get combined and shoved around like a lost piece of avocado in a coconut and mango smoothie, and out the other side come a bunch of energy – but also CO2, and very small quantities of nitrogen and rogue hydrogen (which is combined in part to form ammonia, which gives your urine that lovely pungent smell). Humans don’t live on carbon dioxide or ammonia, so the blood that brought delicious oxygen and water to the cells now picks that CO2 out so it can come out our nostrils, and the kidneys filter the ammonia out and mix it with some water to send it to the bladder. Repeat.

So what does all it mean?
Hopefully it doesn’t surprise you to learn that things that make you breathe faster help you burn more calories. As you exercise, your cells need more energy, which means they need more oxygen and water to use that energy, which means they need to get rid of it faster too.
Water is a key component of the process that creates energy for your cells (amongst many other important things), and without it cell metabolism gets affected hard. Your body has all sorts of water stores in muscles, your blood stream and other organs, which is why you can go a few days without it. But dehydration is dangerous and just going about without enough water in our body means we’ll struggle to get the best energy out of our food.
The metabolism process consumes a lot more oxygen than water. And our bodies have no way of storing oxygen – it attaches itself to a red blood cell in the lungs and gets delivered to another cell somewhere, while the transporting red blood cell hikes some carbon dioxide back to the lungs where it disposes of it. If you hold your breath, CO2 builds up in your blood stream because that red blood cell can’t dispose of it, and goes back to other cells not carrying any new oxygen. Your brain is the organ that consumes the most energy, and it needs a lot of oxygen to create it. Without oxygen, all sorts of things go awry in the brain first, but then everywhere else.
Another interesting thing to ponder is all the “diuretics” and other supplements that promise speed up your digestive system or whatever, all in the name of weight loss. These things tend to wreck all sorts of havoc in the bacteria in our gut and general digestive process. They work in the short term because they’ll mess up water and nutrient absorption, which mean you’ll have fewer calories coming in, which will help you lose weight. But they help you lose weight by affecting how your body naturally processes food, and in the long run they cause more harm than good.
(Please, don’t use this article as an incentive to go after any “CO2 exhaling enhancers” or believe any such thing.)
So there you have it. Eat your veggies, fruit, nuts and some meat in sensible quantities, drink plenty of water, do things that get you puffed. Don’t overcomplicate it, mkay?

As simple as it is, we all need a kick in the bum to get our lungs going. If you would like to have a chat about how best to get that CO2 out of ya, I’m here to help.