Where Does the Fat Go When You Lose Weight?

Did you ever wonder, where does the fat go when you lose weight? There was a survey done of 150 doctors, dietitians and personal trainers. It was surprising to find that even most of them did not have the right answer to this question. Of the 150 questioned, only 3 had the right answer.

The most common misconception by far, was that fat is converted into energy. Many believe that perhaps fat is converted into heat. These assumptions do not regard the law of conservation of matter.

Wikipedia says concerning this law:

The law of conservation of mass or principle of mass conservation … The law implies that mass can neither be created nor destroyed.

What is Fat?

Fat is one of the many types of soft tissue in the body. It supports cell growth, protects your organs, and helps keep your body warm. Fat helps your body absorb some nutrients and produce important hormones.

Triglycerides, cholesterol, and other essential fatty acids are the scientific terms for fats which the body cannot make on its own.

What is a Fat Cell?

As a child, and as you entered puberty, your fat cells were created. Those fat cells remain with you during your lifetime.

Your body stores fat within special fat cells called adipose tissue. Smaller amounts of fat are stored in your liver and muscles as glycogen. Fat cells enlarge when you gain weight and shrink when you lose weight.

If you consume more calories than your body needs, you will gain weight. The body fat stored in those cells will increase. The number of fat cells do not decrease but are always present in the body, or they may create more.

What Is Fat Made of

Fat is made up of carbon, hydrogen, and oxygen atoms.

Losing weight requires the fat to be changed into something else. It cannot just magically disappear. We will discover what the British Medical Journal found out in a 2014 study.

You can read about this in Ruben Meerman’s book “Big Fat Myths: When you lose weight, where does the fat go?” He is an assistant scientist at the University of New South Wales.

When fat is broken down, one-fifth is turned into water (H20) and four-fifths is turned into carbon dioxide (CO2). You cannot turn fat atoms into energy, they must be turned into some other type of matter.


A Lightbulb Moment

Since fat is made of carbon, hydrogen, and oxygen; to lose that fat, you must unlock the carbon, hydrogen and oxygen stored in those fat cells. This is done through a complex body function.

The fat you lose is then converted into water and carbon dioxide!

The By-Products of Fat

The by-products of fat are:

  • water, which is lost through bodily fluids such as urine, feces, breath, sweat, and tears
  • carbon dioxide, which is lost as you exhale

But you must be aware that you cannot lose weight just by huffing and puffing! If you do that, you will just hyperventilate and get dizzy!

By exercising, you increase your use of oxygen and release more carbon dioxide as you breathe. That is one reason why you are encouraged to exercise to assist in weight loss.

Don’t forget that exercise is good for more than weight loss, it strengthens your muscles and bones and makes you healthier in the best way.

As you exhale the carbon dioxide, the water circulates through your body until it is lost as urine or sweat.

If you lose 10 kg of fat…

  • 8.4 kg comes out through your lungs and the remaining
  • 1.6 kg turns into water.

Nearly All the Weight is Exhaled

In other words, nearly all the weight you lose is exhaled.

Where does the fat go when you lose weight? This may surprise many who think that fat is turned into energy. And to think that many health professionals in a survey of 150 doctors, dietitians, and personal trainers, did not have the correct answer to this puzzling question!

Just about everything that we eat comes back out as carbon dioxide, by way of the lungs! Some think fat is turned into muscle and others assume it escapes via the colon.

The only thing that exits via the colon is undigested dietary fiber. When you lose fat, it is absorbed into your bloodstream and organs, as water, and the carbon dioxide is vaporized through your lungs!

So now if you wonder, do you sweat it out, pee it out or breathe it out? The answer is yes.

When You Diet

In the process of dieting, you eat fewer calories than your body needs. Your body must turn to stored fat to get those needed calories to continue functioning properly.

Through a series of complicated steps, it disposes of that fat. The fat cells shrink, but they don’t go away.

If you are carrying extra pounds, it means that you are taking in more calories than you are using. The extra energy is stored in adipose tissue around your body in the form of triglycerides, while smaller amounts are stored in your liver and muscles as glycogen.

The Average North American

North Americans consume about 7.8 pounds of food and beverages each day. Of that about 15 ounces is solid macro nutrients, .6 ounces is fiber, and the remaining 6.9 pounds is water.

It is also important to note that we inhale more than 1.4 pounds of oxygen per day.

If you put in 7.8 pounds of food and water into your body, and 1.4 pounds of oxygen, then 9.2 pounds of something needs to come out if you are not going to gain weight!

Just going about your daily activities will increase your metabolic rate and going for a walk does so as well.

How You Lose Weight

If your lifestyle supplies less “fuel” than you use, you will lose weight. You exhale carbon dioxide and water is metabolized into your system and expelled as urine or sweat.

The only thing that makes it to your colon is undigested dietary fiber. Three-quarters of what makes it from your colon is water. The rest is undigestible fiber in fruit, vegetables, legumes and grains, and a few bits of steak and gristle if you like meat.

You Vaporize Your Fat and Exhale the Atoms

Fat turns into carbon dioxide and water, and nothing else. In other words, Fat + oxygen = carbon dioxide + water.

The air you exhale is heavier than the air you inhale. Carbon dioxide has an extra carbon atom wedged between two oxygen atoms, making up carbon dioxide.


Every carbohydrate and nearly all fats are converted into carbon dioxide and water. Almost everything we eat comes back out by way of the lungs. The small amount of water that is left is secreted as sweat or urine.

Burning Fat While You Sleep

While you are sleeping at night, you exhale 7 ounces of carbon dioxide. That is a quarter of your daily target.

Did you know that you can lose more weight while you are asleep than you do if you are sitting still in your living room? The fact is that you exhale 20 kg of carbon in your sleep every year.

Short Term/Long Term Success

Most popular diets may have short-term success, but fare poorly for maintaining that weight loss. Once they reach the 6-month milestone of their diet it is often difficult to sustain.

Long-term, successful weight loss is achieved by a conscious effort to adopt at least one of these strategies from the following list:

Increase –

  • Fruit and vegetables
  • Exercise

Decrease –

  • Calories
  • Fat
  • Junk food
  • Quantity of food

And you need to maintain that on a consistent basis. It is not surprising that today’s nutrition and health professionals would tell you the same thing!

No diet is considered successful if it is something you cannot live with every day. That is why it is called a lifestyle, because it must be maintained day by day.

Where does the fat go when you lose weight? You can read about it in the book “Big Fat Myths: When you lose weight, where does the fat go?” By Ruben Meerman, an assistant scientist at the University of New South Wales.

If you are curious you can check out the bmj article by Ruben Meerman
and Andrew Brown
“When somebody loses weight, where does the fat go?”

In Conclusion

Losing weight requires unlocking the carbon stored in fat cells. So,The most common misconception by far, was that fat is converted into energy.

Please Leave a Comment

I would love to hear from you. Have you tried successfully to lose weight? What has been your experience?

Disclaimer: If you have any concerns or questions about your health, you should always consult with a physician or other healthcare professional. No content on this site should be substituted for direct medical advice from your doctor or other qualified healthcare practitioners. The information contained here is for informational purposes only. It is from my research and personal experience.

6 thoughts on “Where Does the Fat Go When You Lose Weight?”

  1. This is interesting. I always thought we lost fat through urine and faeces but I just had a light bulb moment. That’s awesome that it’s exhaled through our breath instead. Luckily you said that we have to exercise because I was just about to start breathing heavily to see how much weight I could lose (haha). Thanks for the article, I’ll be back for more.

    • Hi Brandon,

      Thanks for the comment. It was fun working on this post. It was interesting to see how the carbon in the fat is broken down and combined with oxygen so we would exhale the carbon dioxide. Yes, there is no point hyperventilating and getting dizzy trying to lose a pound or two!

      All the best!

      Come back anytime!

  2. This is a fascinating article… I had no idea that we got rid of fat by breathing it out! Great insight into how to lose weight – when you know what’s going on in your body, it makes it easier to visualize the process of sorting it out… I’m intrigued now to read more of your posts! 

    • Hi Mohammad,

      Thanks for stopping  by! Our bodies are a work of art! It is amazing to learn all they can do!

      I enjoyed writing this article and learned a lot as well. That is the fun part of blogging. There is so much to learn.

      All the best,


  3. Wow…how did you even come up with such à question?…I would confess that over the years of going to several gyms and seeing several workout pros, I never thought of the fact that where do fats in our body usually go to when we lose them…and surprisedly, we use these fats for more energy just as much as we need energy to get rid of them…isn’t nature awesome….
    I did really learnt a lot from this article and I hope to see more of your article soon…

    • I must admit I too, found this subject quite interesting. Matter can’t just evaporate into thin air, it has to go somewhere. I found it interesting to know the chemical composition of fat. Carbon, oxygen and hydrogen. Isn’t nature such a wonder!


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