What happens to fat when you lose weight? Where does it go? It obviously doesn’t just disappear into thin air. I was recently asked this question which I was dumbfounded by. This is something I had never thought about before and apparently neither have a lot of other people. The law of conservation of mass tells us that mass (anything made up of atoms) must be conserved meaning it cannot be created or destroyed. Maybe humans got to the top of the food chain with this unknown ability to perfectly turn mass into energy breaking the laws of physics as we know it!!! Or maybe fat just ends up being flushed down the drain… Who knows what happens to the fat that magically falls off our body?!
Eating at a caloric deficiency will lead to weight loss due to our bodies need for an energy source. So of course the fat just becomes energy and gets burnt up, right? Well… not really! When we lose weight we physically lose lbs of our self. Energy is weightless… Hey science Nazi’s! Settle down out there! E-mc2 doesn’t apply here so let’s just stick with Newtonian physics and be on our way… Where was I? Oh yea, Energy is GENERALLY weightless and is measured in joules…. Or what our body knows as calories, not lbs. So since our weight can’t disappear into heat or other forms of energy the question still remains.
Let’s take a look at what fat actually is. Human fat is made up of chains of Carbon, Hydrogen, and Oxygen, pretty standard organic chem stuff so far. The average human fat molecule looks like C55H104O6. The carbon and hydrogen atoms may vary up or down but C55H104O6 is the average of all of our fat. When you hear about saturated, unsaturated, monounsaturated, or triglycerides all of these are referring to the combination of carbon, hydrogen and oxygen.
So we want to know where this stuff disappears to. Well the equation is quite simple.
C55H104O6 + 78O2 à 55CO2 + 52H2O
Better known as
Fat + Oxygen turns to Carbon Dioxide + Water.
Could it be so simple? Basically this equation tells us that when we burn stored body fat we use oxygen inhaled and the fat and convert it into CO2 that we exhale and water. Water may come out as sweat, urine, feces, or even tears of joy from seeing your body transformation, maybe not so much on the last point. This blew my mind! When we work out we are literally sweating our asses off! But also breathing it from our mouth too?
Ruben Meerman went even further to explain how much fat is breathed out and sweated out in his TedTalk video linked. Running through the mass balancing calculation he determined that fat is lost with a ratio of 84% leaving as CO2 and 16% as H2O. So a huge majority is just breathed out! He goes on to explain that we can’t just sit around and “breath more” to lose weight. What is oversimplified in the equation above is that arrow. That arrow represents everything our body is doing in order to break down the fat into the energy, CO2, and H2O. That arrow represents all the biochemistry going on in our body during exercise, all the releases of hormones, the call to break down fat into energy by the process called lipolysis. You need to put your body under the stress of increasing your heartrate and elevating you breathing naturally. Hyperventilating will not cause fat loss.
A quick note on lipocytes also known as fat cells. These can be thought of as the houses that store C55H104O6. Once these cells are formed they can expand and shrink but do not disappear. Procedures such as liposuction goes in and removed the fat cells and many think of this as an extreme solution to obesity. On the contrary removing fat cells will not cause the ones left behind to not expand. To lose weight the healthy way we actually have to shrink the lipocytes by burning up the stored fat energy accumulated over the years.
Although it may just be a bunch of fun facts take a moment and appreciate how incredible your body is! Its innate ability to store excess energy and then consume it when needed blows my mind! The problem is with the average American’s diet we are “storing” way to much energy. We are not bears getting ready for the long winter! Your body is amazing and it’s the only one you’ll ever get so start taking care of it right now. Taking control of your diet and health. Let’s not create any more lipocytes but let’s shrink the ones we have to a nice healthy level! As Ruben put it, “All you need to do is; eat less, move more, and just keep breathing”.