Where Does Fat Go When You Lose Weight?

4 minute read

By Lauren Brown

Many people embark on the journey of weight loss, but few stop to ponder the scientific process behind it. What actually happens to the fat in our bodies when we shed pounds? Start a search online to learn more about what happens during weight loss.

Understanding the biological mechanisms of fat loss is key to demystifying the process. It’s not just about counting calories; it’s a complex interplay of metabolism, energy, and physiology. Let’s unravel the mystery behind it.

What Is Food, Really?

First off, let’s get clear on what fat is actually for and why our bodies make it in the first place. We’ll start with the growling sound our stomachs make when we’re in need of food.

Food, from a biological standpoint, is necessary to supply our body with the essential nutrients required to run all of its functions and processes. These include growing, repairing damage, digesting the food itself, keeping our heart beating, dealing with the bad stuff we ingest over the aforementioned weekend (and on and on), as well as the energy required for us to exist and perform all of our daily tasks and demands.

Food consists of micronutrients (vitamins and minerals), as well as macronutrients (carbohydrates, fats and protein). And depending on how processed it is, food might also contain chemicals, preservatives, colorants, etc., which is a discussion for another time. When broken down, macronutrients are a source of energy for the body (in addition to many other things) in the form of calories. To introduce a bit of physics into your day, one calorie is approximately the amount of energy required to raise one gram of water by one degree Celsius. Don’t you feel so much smarter now?

So, What Is Fat?

Anyway, when the body has divvied out the energy needed to fulfill the requirements of all of our cells and their roles, the spare energy is stored for later on down the road for when we might need it – i.e. if we ever run out of food. For a number of us in North America, this isn’t necessarily our reality, so over time we create a larger and larger hoard of energy – all in the form of fat.

Now, the fat isn’t roaming around willy nilly under our skin. It’s stored in its tiniest molecular form, called a triglyceride, which is a chain of three carbon atoms (called glycerol) attached to three fatty acid molecules. A bunch of these together form a lipid droplet and are stored in one of the body’s fat cells called an adipocyte.

The more excess fat you create, the more fat cells the body has to make to house it all (versus just shoving more and more fat molecules into a set number of adipocytes). And as all of us know, we are all entirely different in where our body chooses to distribute those cells…

Where Does the Fat Go When You Lose Weight?

But what is happening inside when you do bust your butt (like, literally) and are able to burn off some of those fat stores? Where does the fat actually go?

Well that process, my friends, is called lipolysis, (note: genesis = make, lysis = break down) and it’s pretty darn cool. When our body needs to dip into its energy bank because we’re either limiting the calories we consume, or are burning off more than we have taken in (or both), it breaks down those triglycerides back into their building blocks (i.e. the glycerol and fatty acid molecules) using enzymes called lipases.

The free fatty acids (FFAs) are then released from the adipocyte to travel along the bloodstream to our hungry cells. Once they arrive, the cells happily take them in and bombard the FFAs with oxygen molecules (a process called oxidation).

After this, they go through a series of complicated steps beyond what we’ll discuss here (hellllo, organic chemistry!) and end up being made into carbon dioxide, water and energy for the cells. That means our fat stores are actually released when we exhale (84%) and through our sweat and urine (16% combined)! Who would have thought?

Fat Cells Are Here to Stay

There are some interesting facts to note about losing weight and burning fat. Once your body has used up the triglycerides in your adipocytes, the empty cells do not disappear. They still hang out, albeit empty, and wait until they’re needed again. That means every fat cell you create during your lifetime (and it’s a supply and demand sort of deal) you will NEVER BE RID OF, even for all the hard work you do to empty them of their contents. That’s inspiring, now isn’t it? Oh dear.

Insulin Can Create Roadblocks to Weight Loss

Secondly, insulin, the hormone our pancreas makes to help glucose get into cells, actually messes with how much fat we burn. It carries out its evil plan by limiting the function of the lipase enzymes used during lipolysis, leaving it difficult for the body to break down fatty acids into their usable form. AND insulin increases fat production and storage by stimulating the activity of a key enzyme associated with lipogenesis. So we can now see why avoiding sweets is an effective tool in helping us lose weight!

Perseverance Is Key

The last tidbit that is kinda interesting is that for every one gram of fat burned, nine calories of energy are released into our cells, versus carbohydrate stores, which only give up four calories per gram. That being said, carb calories are easier for the body to assimilate, and unfortunately, our body resorts to these stores (found in the muscles and liver) first before it turns to those fat ones.

You might even notice it when working out: all of a sudden you’ve gone from feeling sort of OK to the sensation of pulling a flatbed loaded with boulders behind you. But if you’re trying to slim down, perseverance (in a healthy way!) will pay off.

Now, my friends, go get sweaty!

Lauren Brown MSc. WWHP, is a certified Health & Wellness Coach who loves teaching about all facets of health and wellbeing. Much of her time is spent in workplaces, helping empower employees to get healthy through the wellness programming initiatives and educational sessions she delivers. Please see www.inspiringhealth.ca for more information.

Lauren Brown