Metabolism: Seriously, what’s this all about?

Lets play a quick game. Which of these have you heard before (variations count):

  • “I’m only overweight because my metabolism is so slow.”
  • “This new pill will SKYROCKET your metabolism!”
  • “People with high metabolisms are naturally skinny, so they don’t need to workout.”
  • “I have a high metabolism, so I just eat everything.”
  • “It’s not about what you eat or do, it’s about your metabolism.”

Between social media, news media, advertising, and other people in the gym, I’m sure you’ve heard most – if not all – of these at least once. The overriding theme is, of course, this mysterious thing called your “metabolism” that apparently is the Only Thing In the World That Matters for your health and wellness. From diet pills that promise to boost your metabolism by 600% to diet plans that purport to increase resting metabolism to super-high levels of fat burning awesomeness, metabolism gets a big slice of the fitness advice pie.

But, seriously, what’s this all about? Stand back people, we’re about to Science! (Yes, I just used “science” as a verb. I’m a hardcore nerd; I’m allowed.)

What is Metabolism?

Metabolism has one of two word origins, both Greek: “metabolē” which means “change”, or “metabolismos” which means “out-throw”. The modern word refers to nothing less than the sum of all chemical reactions in your body that occur to sustain life, including growth, reproduction, structural stability, and responding to environmental changes. If that sounds like a huge amount of stuff being described in just one word, that’s because it is! Essentially, your metabolism is almost everything your body does in order to Not Die.

That’s a very broad definition, so lets break it down a bit more and see how many licks it takes to get to the center of this Tootsie Pop. Today we’ll be covering the two metabolic categories.

Metabolism Categories

There are two types of metabolism which we can call out: Catabolism and Anabolism. These are the two sides of the metabolic coin, with one being responsible for breaking down stuff and the other being responsible for building new stuff. They’re your body’s Yin and Yang. You might recognize the root words as belonging to different steroid groups. Catabolic steroids (also called corticosteroids) break down muscle mass to reduce significant swelling, and to treat autoimmune diseases or severe asthma. Anabolic steroids are used to treat muscle loss from diseases like AIDS or to aid males who fail to go through puberty correctly. They are also the type used to cheat at body building and strength gain (which is still illegal, by the way).

Catabolism, the Breaker

Stemming from the Greek words “kata” meaning “downward” plus “ballein” meaning “to throw”, this is the process that breaks down molecules into smaller parts in order to release energy. Generally, in order to do something your body needs enough energy to affect some kind of chemical reaction. The catabolic pathways are what takes things like sugars and uses them to produce energy. Digestion is a gross (meaning “large”, not “disgusting”) is a good example mechanism that directly affects your health, and can be controlled based on what you feed into it.

Food is broken down into macro-nutrients (what we commonly know as Fat, Protein, and Carbohydrate). These dietary compounds are then broken down even further into polymers (meaning “many parts”) including polysaccharides (complex sugar), lipids (like body fat), nucleic acids, and proteins. Polymers are then broken down even more into monomers (meaning “one part”) like monosaccharides (simple sugars), fatty acids (simple fats), nucleotides, and amino acids.

Once the body has the monomers, it has the building blocks it needs to do one of two things: produce energy or build new polymers. We’ll cover the building piece in the section about Anabolism, but lets talk about energy production now.

Once your body has some spare monomers laying around, it can get on with producing energy by breaking them apart even more. The breakdown of monomers creates three things: cellular waste products, heat, and ATP.

Common Waste Products:

  • Lactic acid: The junk that builds up in your muscles when you workout, causing that feeling of soreness during recovery as it drains off into the body.
  • Acetic acid: Produced, for instance, during the breakdown of alcohol. It can be used to form fatty acids or further broken down into carbon dioxide and water.
  • Carbon Dioxide: Produced by all kinds of processes and removed from the lungs as you breathe.
  • Urea: This is a mostly neutral compound that is used to remove other waste from the body, like nitrogen and ammonia, without harming the cells, through urination and sweating.

A nifty thing you get when you break down a monomer is energy. I won’t hearken too far back to biology 101 here to keep it simple(ish). Basically, the process of breaking apart atoms and molecules acts as a really, really small explosion. Some of the energy in that mini-explosion is lost as heat, but most of it goes directly into creating ATP (or adenosine triphosphate, if you’re curious). This awesome little molecule is what provides the energy for all the cool stuff that Anabolism does in the next section.

Anabolism, the Maker

Coming from the Greek words: “ana-” meaning “upward” and “-ballein” which means “to throw”, it can also be known as constructive metabolism. The ATP which is produced during the catabolic cycles above is used to fuel the build up of organs and tissues in the body. This process takes a lot of energy and is what causes growth of skeletal muscle, bone, smooth muscle, etc. For the most part, if your body needs to build something big from smaller pieces, you’re pumping ATP into the anabolic cycle to get it done.

Honestly there’s a lot that goes into this part of the process; way too much for this article. Here’s an overview of some stuff anabolic processes accomplish in your body:

  • Gluconeogenesis: Converting monomers into glucose, which is then used to maintain blood sugar levels.
  • Fatty Acid Synthases: Used to create the fat tissue that stores long term energy.
  • Protein biosynthesis: Used to build up muscle tissue, for growth or repair.

And that’s it! Here ends our primer on metabolism. There’s so much more to go into, but this enough science for one week. Next week we’ll go into how it’s regulated in the human body and how you can affect it!