How Do We Acquire and Use Energy From Food? Part 1

Ever think about how we, as the crazy people we are, get energy to do everyday stuff? Walk, run, jump, pick up kids, throw said kids because they’re annoying, even getting out of bed! Everything you do takes some bit of energy!

Where do we get that energy? Caffeine? Well, it may seem like it, but caffeine provides no ACTUAL energy. It’s just a stimulant that makes you FEEL energized. There’s a huge difference. We derive our energy from food in the form of calories from carbs, protein, and fat (and alcohol)!

But, let’s dig deeper..how exactly does your body break food down into components that it can use for energy? More importantly, why is this important? Well, if you know what and how your body fuels itself, you can provide it better fuel at better times to feel better, without stimulants!

So, what gives us the energy to live the awesome lives we live? These awesome things known as energy systems!

Energy systems are typically discussed in the context of exercise because that’s one of the few times that all the systems may be utilized during one time period. Typically, at rest, only one (aerobic glycolysis) is used; but, keep this in mind, whenever you’re doing strenuous work like moving or lifting heavy objects, the other sports-related systems may be in use.

There are a few ways our bodies use the different fuel sources. It all depends on the activity you’re doing and the amount of energy needed to perform that activity. Let’s begin by talking about what our body actually uses as energy. Hint: It’s not glucose (technically).

ATP

ATP is THE energy molecule. Whenever we’re doing literally anything, we’re using ATP. While we can acquire ATP from different forms (carbs, fat, protein, alcohol, etc.), it all funnels into ATP and some other secondary molecules. This happens because we have different systems in our bodies to break down the different macronutrients. With that in mind, let’s talk about what they are, when they’re used, and why this applies to you.

In part 1 of this series, I’ll talk about the exercise-focused energy system, Anaerobic Glycolysis; but remember, whenever you’re doing intense, strenuous work, these systems are working, so don’t skip this if you don’t exercise! Part 2 will cover the more general system known as Aerobic Glycolysis.

Anaerobic Glycolysis

To begin, we discuss Anaerobic Glycolysis. This refers to systems that generate energy WITHOUT the use of oxygen. Oxygen is the primary distinction between aerobic and anaerobic systems. Oxygen as a chemical has some interesting properties to it that allows us to create energy in different ways. The next two systems-Creatine Phosphate and Lactic Acid Cycle-do not need oxygen to create energy. Let’s begin!

Creatine Phosphate System

This is the very first system used when doing typically high-intensity exercise or activity. Anything from deadlifting 1000lbs to picking up some heavy furniture. This system is used for, as Deadpool says, MAXIMUM EFFORT. Creatine phosphate is made up of a few atoms-the things on the periodic table-to make a molecule (Chemistry 101 lesson right there, you’re welcome). This molecule, Creatine Phosphate, will donate some atoms to make ATP.

All of this occurs inside the muscle tissues, so energy is able to be generated very quickly, hence why it’s used first; but there is a very limited supply of creatine phosphate in muscles, so this system will deplete in a matter of seconds. So why does this matter? Well, if you’re an athlete, or someone who just likes to exercise (running, lifting, etc.), then this is what jumpstarts you whenever you start your exercise! If you’re going to sprint, that quick jolt of energy is this system at work. Knowing what systems are at work can allow you to better fuel up for training! Creatine is most commonly found in meats. Vegans and vegetarians may have to supplement it.

Creatine supplements work by flooding your muscles with creatine, thereby allowing this system to last longer than a few seconds and continue to produce energy quickly which can lead to better training sessions since your endurance is improved! This is some seriously cool stuff. Think about it next time you pick up something heavy, or move some furniture!

Lactic Acid Cycle

After the Creatine Phosphate system is exhausted, the body shifts over to the lactic acid cycle for up to roughly 2 minutes of continuous work (think two minute run or two minutes straight of lifting). This is typically when someone will start to “Feel The Burn”, especially in terms of weight training. The reason this occurs is because there is an accumulation of hydrogen in the muscles, which causes the muscle tissue environment to become more acidic.

What this results in is that fatigue and tiredness experienced when lifting weights. The acidic environment inhibits the working muscles from contracting and causes that burning sensation and fatigue.

So why do we use this system if it’s just going to burn us? That’s some BS.

Not quite, dear reader!

The lactic acid cycle is great in its ability to produce energy quickly and for a relatively long time. If we couldn’t produce energy this way, we’d be pooped much quicker. Here’s how it works:

The cycle is between the working muscles and your liver. The things that are cycling are glucose and lactate. Remember glucose? That’s the primary source of energy and ATP and guess what? It still is in this case! As glucose enters the muscle cell, the glucose will produce some ATP for the immediate energy demand and then be converted to lactate.

Then, this lactate will travel to the liver to be converted back into glucose. When converted back to glucose, the lactate also produces some ATP for immediate use. The lactate (now glucose) will travel back to the muscle cell to produce more ATP and continue the cycle until the hydrogen atoms inhibit further muscle contractions.

As you can probably imagine, this system pretty much produces energy on demand, meaning that there is none stored for future use. The ATP that is synthesized is immediately used.

Takeaways

Once again, this system only lasts for a few minutes, then the aerobic glycolysis systems kick in and produces a TON of energy but at a slow pace. This will be the topic for part 2 next week! Stay tuned! Check out my other articles about the sources of ATP (Protein, carbs, and fat) to learn more about the awesomeness of our body’s interaction with food! Thanks for reading!

  • The body utilizes the macronutrients through different energy systems for different demands of energy
  • Higher energy demand is derived from anaerobic glycolysis systems
  • The Creatine phosphate system is the initial system used for high-intensity work but only lasts a few seconds
  • The Lactic Acid Cycle allows us to work at high intensities for a couple of minutes until muscle contraction is no longer possible. This is accomplished by cycling glucose and lactate between the liver and muscle cells.

 

2 Comments

  1. Very informative about the main sources of where the human body receives it’s energy, and the systems that it uses. The only couple of things I was missing in the article were: what the acronym ATP stands for to possibly understand it further simply through its name, and exactly how caffeine makes us “feel” now energized. I was expecting more about caffeine throughout the article based on the intro. However, I’m looking forward to part two.

    Liked by 1 person

    1. Thanks for the feedback. I’ll include a description on ATP in part 2!

      Caffeine is only a stimulant. Typically, it contains little to no calories, which is what contains the protein, carbs, fats, etc. that our body can actually break down to create energy. The stimulant factor of caffeine is more so an effect on the brain’s perception of energy rather than actual energy!

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