The Pulse


Where Does Lost Fat Actually Go?

by Patrick Reynolds

Here at Kenzai headquarters we spend all day, every day, looking at the human bodies at various sizes and weights. When you spend that much time with the body, adjectives tend to drop away. Words like "fat" and "skinny" go completely unused here. You will hear the word "biomass" quite a lot however.

I don't walk around the world seeing fat and thin people. I walk around the world seeing people who are carrying various amounts of biomass on their frames. Some of them want some help getting this biomass off their frames, and they come to us to help them do it. And at point we have a physics problem on our hands, one of which we know all the numbers and equations.

The truth is, breaking up fat stores and shifting biomass off a person is not particularly difficult. It's just energy in vs. energy out, while keeping one eye on the levels of lipids, amino acids, vitamins and minerals. This is the easy part. What's challenging is giving that person systems that motivate them to keep hitting the right numbers, week after week, because short of cutting off a leg, shifting biomass takes time.

A study recently came out that put a delightful new spin on the work of moving biomass from within the body to the world outside. It was published in the British Medical Journal and is happily not behind a subscription wall so you can read it here if you have the same passion for stoichiometry as I do. If not, I'll break it down in layman's terms for you.

The study started with a simple question. When someone loses biomass in the form of body fat, where exactly does that mass go? We know it's not just disappearing, the law of conservation of mass is called a law for a reason. So it must be leaving the body somehow.

The researchers asked medical doctors, nutritionists, and trainers, and almost all of them made the same mistake. The majority of them thought that the mass was converted to energy. On its face, this seems logical. When you're running a caloric deficit during your training diet, the body needs to find the energy to maintain itself. So it takes the triglyceride fat packets, breaks them apart with a catabolic reaction, and uses that energy to power metabolism. So the mass becomes energy... right?

This is about the time a pesky equation noisily clears its throat and brings the party to a halt.

E = mc²

Energy and matter are deeply related. The mass of an object times the squared speed of light will give you the energetic potential of that object (in joules). These numbers are always pretty shocking when you run them through the equation.

For example, let's say that Albert loses 5kg (11lb) on his training program. If that 5kg were converted directly into energy it would unleash the equivalent of 100 megatons of TNT. For perspective, that's twice the energy of the biggest nuclear bomb ever tested (Russia's Tsar Bomba) and 5000 times the energy of the bombs dropped on Hiroshima and Nagasaki.

So Albert's fat mass couldn't have been transformed to energy. If that's how things worked, every time someone went on a health kick they'd end up levelling their neighborhood.

So where is the mass going? The researchers carefully charted the course of the atoms of an average triglyceride packet and found a surprising result. Are you ready for this?

Of all the atoms in the 5kg of fat that Albert loses, 4.2kg of it will be exhaled from the lungs in the form of CO2. You exhale 84% of lost fat through your lungs! That's where all that biomass is going. It's being broken down into carbon dioxide and pumped out into the air around you!

And how about that other .8kg? It's packed up into H20, and excreted from your body through urine, feces, sweat, or other bodily fluids. And that's it. Fat turns mostly into exhaled carbon dioxide and a little water. As the research paper summed up, "The lungs are the primary excretory organ for weight loss." Isn't that fabulous!?

It doesn't take long for people to look at these results and think... "so, if I breathe a lot more will I lose some extra fat?" Sadly, no. The fact that the fat packets are being used at all is the result of a body doing exercise and not having enough calories in the system to meet energy needs. You can't cheat your way around that reality. This study won't spare you from the sacrifice and exertion of training, all it is shows exactly how all that biomass is getting from inside your body to the outside.

I don't know about you, but seeing the body like this is incredibly inspiring for me. We're made of simple matter and powered by the energy of our little star, and our bodies follow the same exact rules as the rest of the universe. We aren't special, our bodies aren't mysterious black boxes that we have to be superstitious about, they're bound to the same limits of all matter. And with our intellect we can understand these limits and work with them to feel happy and healthy in our few years of life. All too soon not just our fat, but our skin, organs, and eventually bones will break down into their constituent atoms and be scattered across the planet. And the planet will also be broken up one day and diffused across galactic space.

This is an awe-inspiring dance of time, space, matter and energy, and we have the privilege to be a part of it. I'd like to do that dance not weighed down with a lot of useless biomass hanging off me. Let's mobilize that fat with a clean diet and daily exercise, and end the day with a sigh of satisfaction, a sigh that carries with it the molecules that once were sticking to our bodies!

Bonus: critical thinking challenge! If you're putting out all this extra CO2 from breaking down fat, are you contributing to global warming when you slim down?

Answer: No! Let's say you got fat eating sweet potatoes. Plants live on CO2. The potatoes took atmospheric carbon and incorporated it into their mass to grow. You then ate the potatoes and sequestered that carbon into your own body in the form of fat. Finally you exercised, broke up that fat, and exhaled most of it back into the atmosphere.

This is a closed carbon cycle, with no extra CO2 being added to the system, hence no global warming. Global warming is caused by accessing vast amounts of CO2 that used to be locked away in the earth's crust and shifting it to the atmosphere, not from organic plants and animals cycling it through their bodies as energy and waste.

If you wanted to split hairs, you could argue that because the sweet potatoes were tilled by a tractor and came to you on a truck they aren't really carbon neutral, but that's not the potatoes' fault.



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