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Obesity is one of the major health concerns all over the world, and people strive to lose that extra fat to live a fit and healthy life. But, to say the least, very few actually understand the process of fat loss and how it happens in the human body.

Therefore, this article seeks out the actual fat loss process to make you understand the mechanism behind it. By understanding how fat is stored and burned by the body, you will  know how to control your body fat levels. Of course, it is a highly complex process, but you don't need a degree in medical sciences to understand how it works. Understanding the basic principles will help you in your fat loss journey and live a fit and healthy lifestyle.

How You Gain Fat in the First Place?

Before understanding the fat loss process, you need to know how you gained fat in the first place, and for that, you need to know the concept of calories in and calories out.

The food that you eat contains energy (measured in calories). You use that energy throughout the day to move your body and do regular work like walking, working, working out, etc.

Therefore, when you consume extra calories that your body uses throughout the day to fuel your daily activities (also called caloric surplus), it gets stored in the form of triglycerides in the body fat cells.

This is because your body preserves these calories (energy) for future needs. Over time, if you continue eating excess calories, your fat cells start expanding. The continuous storage of fat cells changes your body composition, and you gain fat around your body.

What Happens to the Calories in Your Body?

The energy contained in the foods and drinks you consume either goes straight into your bloodstream for immediate use, or it will be used to replenish energy stores in places like your muscles and liver and, once those stores are full, it gets stored as energy in your fat cells.

It's important to note that you're both storing and using energy simultaneously at any given moment. You always need some fuel just to stay alive and perform any activity. But the less active you are and the more energy intake, the more of a surplus of energy you have in your system and the more energy your body will store for later in your fat cells.

So, How Does Fat Loss Takes Place?

First, to promote fat loss, you need to be in a caloric deficit, meaning you need to burn more calories than you consume.

So, your body first uses the energy stored in your bloodstream and muscle before tapping into the fat stores. This is because your body treats fat cells as reserved energy to be used in the future, and the energy in your muscles and bloodstream (also called glycogen) is for immediate uses.

Fat Loss3

Once your body starts tapping the fat stores for energy, the fat is released from the cells and reaches mitochondria and broken down to produce energy. And as you continue being in a calorie deficit, more fat cells get engaged to fuel your body daily activities. But the fat storage cells don't actually disappear; only the stored fat gets removed and used as energy. Therefore, to get lean, you need to keep shrinking those cells by maintaining a deficit.

So, Where Does Fat Go?

The science behind this procedure is a bit complex. But keep in mind that the fat stored in your cells will eventually be broken down into its components - carbon, hydrogen, and oxygen.

The compounds that your body does not use are excreted. You either breathe it out (carbon dioxide) or excrete it as water (through your urine, sweat, etc.

Would You End Up Burning Muscles?

When it comes to losing fat, you may be concerned about losing your hard-earned muscle tissues also. And your concern is justified too. When the energy reserves in your blood run out, your body can resort to your muscles for energy, resulting in muscle tissue being "burned up" as fuel. Of course, this is the last thing you want since it will not only make your body composition worse, but it will also cause your metabolism to slow down, which means your body will burn less energy in the future.

However, you can prevent this from happening by fueling your diet with enough protein from foods like eggs, meat, dairy, soya, etc.

healthy food high protein

Protein will help to build and maintain muscle mass while being on a fat loss.

The Bottom Line

While it may sound simple to burn fat and make it disappear, everyone who has been on a fat loss knows how complicated it can get.  Unfortunately, there is no quick fix for this: You need to count your daily calories to stay in a deficit in conjunction with a workout plan and stay active through the day to ensure a healthy, sustained rate of fat loss.

If you’re looking to lose fat but are unsure of the best ways to do it, read our previous articles on varied topics to suit what is best for you like; The 12 Main Reasons You Are Not Losing Weight and Intermittent Fasting: What It is? & What It Isn’t?. We have also collated and researched topics on some effective ways for fat loss which can interest you as well. Read our blogs like How to Shred Body Fat Quickly?, The  Fat Loss Pyramid – Manage Your Nutrition, Workouts and Supplementation! etc. and pave your way to a healthy life.


Howell, S., & Kones, R. (2017). "Calories in, calories out" and macronutrient intake: the hope, hype, and science of calories. American Journal of Physiology-Endocrinology and Metabolism, 313(5), E608–E612.

Cox, C. E. (2017). Role of Physical Activity for Weight Loss and Weight Maintenance. Diabetes Spectrum, 30(3), 157–160.

van Baak, M. A., & Mariman, E. C. M. (2019). Mechanisms of weight regain after weight loss — the role of adipose tissue. Nature Reviews Endocrinology, 15(5), 274–287.

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