The funny thing about weight loss is, as much as many of us desperately want it to happen, we often don’t actually notice when it does. Sure, there’s always the number on the scale, but that never tells the whole story. It’s only when your pants become way too loose or someone points it out that you realise how much you’ve shed. Body fat creeps up out of nowhere and disappears in the same way. But the question of the century is—where does fat go when you lose it? Does it evaporate into thin air? Does it get released in our sweat or… other bodily fluids?
It’s something most of us have briefly considered at one point or another—before throwing it in the ‘too complicated’ basket and moving on with our lives. And it appears we’re not the only ones. In a study from the Univesity of New South Wales, even the 150 doctors, dietitians and personal trainers surveyed couldn’t explain where fat goes you lose it. Only three of the respondents gave the right answer, which means 98% of health professionals surveyed could not explain how weight loss works. Some respondents thought fat turns into muscle, which is impossible, and others assumed it escapes via the colon. Yikes.
So, what actually happens to the fat when you lose it? In a piece for The Conversation, two UNSW scientists, Ruben Meerman and Andrew Brown, give us the lowdown:
“The correct answer is that fat is converted to carbon dioxide and water. You exhale the carbon dioxide and the water mixes into your circulation until it’s lost as urine or sweat. If you lose 10kg of fat, precisely 8.4kg comes out through your lungs and the remaining 1.6kg turns into water. In other words, nearly all the weight we lose is exhaled. This surprises just about everyone, but actually, almost everything we eat comes back out via the lungs.
Every carbohydrate you digest and nearly all the fats are converted to carbon dioxide and water. The same goes for alcohol. Protein shares the same fate, except for the small part that turns into urea and other solids, which you excrete as urine.”
Yep, you read that correctly—the majority of fat comes out through your breath. Crazy, right!? So, does that mean the key to becoming shredded is simply breathing more?
“Huffing and puffing more than you need to is called hyperventilation and will only make you dizzy, or possibly faint. The only way you can consciously increase the amount of carbon dioxide your body is producing is by moving your muscles.”
However, the scientists note that getting enough shut-eye can also help you lose fat, as “you exhale 200g of carbon dioxide while you’re fast asleep every night, so you’ve already breathed out a quarter of your daily target before you even step out of bed.” So, while the fact that fat comes out through your breath may be groundbreaking to some, the fundamentals of weight loss remain the same—eat less kilojoules than you burn and get plenty of sleep and you’ll be well on your way!