Most health professionals lack a clear understanding of how body fat is lost, often subscribing to misconceptions like fat converting to energy or muscle.
The truth is, fat is actually broken down into carbon dioxide and water, with the majority of the lost fat being exhaled as carbon dioxide. This insight is crucial for understanding the real mechanics behind weight loss and dispelling common myths.
Unveiling Weight Loss Misconceptions
The world is obsessed with weight loss and fad diets, yet few people actually understand where fat goes when we lose weight.
Even among 150 doctors, dietitians, and personal trainers we surveyed, this knowledge gap was surprisingly common. The most widespread myth was that fat is converted into energy. However, this idea contradicts the law of conservation of matter, which all chemical reactions obey.
Some respondents believed fat transforms into muscle, which is impossible, while others assumed it exits through the digestive system. In reality, only three people in our survey got the correct answer. That means 98% of these health professionals couldn’t accurately explain how weight loss works.
So if fat isn’t turned into energy, muscle, or waste, where does it actually go?
The Surprising Science of Fat Loss
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 10 pounds of fat, precisely 8.4lb comes out through your lungs, and the remaining 1.6lb 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.
The only thing in food that makes it to your colon undigested and intact is dietary fiber (think corn). Everything else you swallow is absorbed into your bloodstream and organs and, after that, it’s not going anywhere until you’ve vaporized it.
Understanding Energy and Weight Dynamics
We all learn that “energy in equals energy out” in high school. But energy is a notoriously confusing concept, even among health professionals and scientists who study obesity.
The reason we gain or lose weight is much less mysterious if we keep track of all the kilograms, too, not just those enigmatic kilojoules or calories.
According to the latest government figures, Australians consume 3.5kg of food and beverages every day. Of that, 415 grams is solid macronutrients, 23 grams is fiber and the remaining 3kg is water.
What’s not reported is that we inhale more than 600 grams worth of oxygen, too, and this figure is equally important for your waistline.
The 415 grams of carbohydrates, fats, protein, and alcohol most Australians eat every day will produce exactly 740 grams of carbon dioxide plus 280 grams of water (about one cup) and about 35 grams of urea and other solids excreted as urine.
An average 75kg person’s resting metabolic rate (the rate at which the body uses energy when the person isn’t moving) produces about 590 grams of carbon dioxide per day. No pill or potion you can buy will increase that figure, despite the bold claims you might have heard.
The good news is that you exhale 200 grams 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.
Active Solutions to Weight Loss
So if fat turns into carbon dioxide, could simply breathing more make you lose weight? Unfortunately not. 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.
But here’s some more good news. Simply standing up and getting dressed more than doubles your metabolic rate. In other words, if you simply tried on all your outfits for 24 hours, you’d exhale more than 1,200 grams of carbon dioxide.
More realistically, going for a walk triples your metabolic rate, and so will cooking, vacuuming, and sweeping.
Metabolizing 100 grams of fat consumes 290 grams of oxygen and produces 280 grams of carbon dioxide plus 110 grams of water. The food you eat can’t change these figures.
Therefore, to lose 100 grams of fat, you have to exhale 280 grams of carbon dioxide on top of what you’ll produce by vaporizing all your food, no matter what it is.
Any diet that supplies less “fuel” than you burn will do the trick, but with so many misconceptions about how weight loss works, few of us know why.
Written by:
- Ruben Meerman, Assistant scientist, UNSW Sydney
- Andrew Brown, Professor and Head, School of Biotechnology and Biomolecular Sciences, UNSW Sydney
Adapted from an article originally published in The Conversation.
News
Scientists Flip a Gut Virus “Kill Switch” – Expose a Hidden Threat in Antibiotic Treatment
Scientists have long known that bacteriophages, viruses that infect bacteria, live in our gut, but exactly what they do has remained elusive. Researchers developed a clever mouse model that can temporarily eliminate these phages [...]
Enhanced Antibacterial Polylactic Acid-Curcumin Nanofibers for Wound Dressing
Background Wound healing is a complex physiological process that can be compromised by infection and impaired tissue regeneration. Conventional dressings, typically made from natural fibers such as cotton or linen, offer limited functionality. Nanofiber [...]
Global Nanomaterial Regulation: A Country-by-Country Comparison
Nanomaterials are materials with at least one dimension smaller than 100 nanometres (about 100,000 times thinner than a human hair). Because of their tiny size, they have unique properties that can be useful in [...]
Pandemic Potential: Scientists Discover 3 Hotspots of Deadly Emerging Disease in the US
Virginia Tech researchers discovered six new rodent carriers of hantavirus and identified U.S. hotspots, highlighting the virus’s adaptability and the impact of climate and ecology on its spread. Hantavirus recently drew public attention following reports [...]
Studies detail high rates of long COVID among healthcare, dental workers
Researchers have estimated approximately 8% of Americas have ever experienced long COVID, or lasting symptoms, following an acute COVID-19 infection. Now two recent international studies suggest that the percentage is much higher among healthcare workers [...]
Melting Arctic Ice May Unleash Ancient Deadly Diseases, Scientists Warn
Melting Arctic ice increases human and animal interactions, raising the risk of infectious disease spread. Researchers urge early intervention and surveillance. Climate change is opening new pathways for the spread of infectious diseases such [...]
Scientists May Have Found a Secret Weapon To Stop Pancreatic Cancer Before It Starts
Researchers at Cold Spring Harbor Laboratory have found that blocking the FGFR2 and EGFR genes can stop early-stage pancreatic cancer from progressing, offering a promising path toward prevention. Pancreatic cancer is expected to become [...]
Breakthrough Drug Restores Vision: Researchers Successfully Reverse Retinal Damage
Blocking the PROX1 protein allowed KAIST researchers to regenerate damaged retinas and restore vision in mice. Vision is one of the most important human senses, yet more than 300 million people around the world are at [...]
Differentiating cancerous and healthy cells through motion analysis
Researchers from Tokyo Metropolitan University have found that the motion of unlabeled cells can be used to tell whether they are cancerous or healthy. They observed malignant fibrosarcoma [...]
This Tiny Cellular Gate Could Be the Key to Curing Cancer – And Regrowing Hair
After more than five decades of mystery, scientists have finally unveiled the detailed structure and function of a long-theorized molecular machine in our mitochondria — the mitochondrial pyruvate carrier. This microscopic gatekeeper controls how [...]
Unlocking Vision’s Secrets: Researchers Reveal 3D Structure of Key Eye Protein
Researchers have uncovered the 3D structure of RBP3, a key protein in vision, revealing how it transports retinoids and fatty acids and how its dysfunction may lead to retinal diseases. Proteins play a critical [...]
5 Key Facts About Nanoplastics and How They Affect the Human Body
Nanoplastics are typically defined as plastic particles smaller than 1000 nanometers. These particles are increasingly being detected in human tissues: they can bypass biological barriers, accumulate in organs, and may influence health in ways [...]
Measles Is Back: Doctors Warn of Dangerous Surge Across the U.S.
Parents are encouraged to contact their pediatrician if their child has been exposed to measles or is showing symptoms. Pediatric infectious disease experts are emphasizing the critical importance of measles vaccination, as the highly [...]
AI at the Speed of Light: How Silicon Photonics Are Reinventing Hardware
A cutting-edge AI acceleration platform powered by light rather than electricity could revolutionize how AI is trained and deployed. Using photonic integrated circuits made from advanced III-V semiconductors, researchers have developed a system that vastly [...]
A Grain of Brain, 523 Million Synapses, Most Complicated Neuroscience Experiment Ever Attempted
A team of over 150 scientists has achieved what once seemed impossible: a complete wiring and activity map of a tiny section of a mammalian brain. This feat, part of the MICrONS Project, rivals [...]
The Secret “Radar” Bacteria Use To Outsmart Their Enemies
A chemical radar allows bacteria to sense and eliminate predators. Investigating how microorganisms communicate deepens our understanding of the complex ecological interactions that shape our environment is an area of key focus for the [...]
