How your Body Makes and Spends Energy
And how to regain your spark
What’s inside today ☑️
This edition is packed with information on how to regain your energy back. Learning how your body works empowers you take action and live a full life every day.
How You Make Energy
Mitochondria produces ATP—your body’s energy currency—via aerobic respiration from food and oxygen.
How You Store & Use Energy
Your body stores energy short-term as glycogen and long-term as fat. Your body stores unused energy which affects energy production and overall vitality.
Why You Still Feel Tired
Modern fatigue is often not physical depletion but the result of cognitive overload, poor sleep, nutrient gaps and inactivity.
What You Can Do
Learn how your body works, reconnect with natural rhythms and adopt simple, evidence-based strategies to recharge your energy effectively.
There are days when I wake up and, from the moment I open my eyes, I just know I’m ready to handle whatever comes my way—even when my smart watch might say otherwise. I roll out of bed and into my morning routine and the day just flows as I tick off my tasks.
But then there are those days when I wake up feeling groggy—my body feels heavy, my head foggy, I struggle to get out of bed. As I go through my usual morning routine—hydrating, moving, meditating—something doesn’t feel right. This is when I know yesterday’s choices—eating high carb or high fat meals, going to bed late at night—are catching up with me. Through the day, I force myself to be productive, but my brain doesn’t want to cooperate. I zone out every 15 minutes and, deep down, I just know my body’s asking for a break. But what do I do instead? The same thing we all do: keep pushing, becoming trapped in the perpetual ‘boom and bust’ cycle.
It feels like our modern day lives don’t give us any other choice. But is this really true?
In our last post, we mapped out the different dimensions of human energy and why understanding our energy in relation to our modern society is key to our survival.
Today we’ll continue by going back to the basics and answering a simple question:
How do our bodies create, store and spend energy every day?
First, we’ll dive into the amazing work our body does just to keep us alive.
Second, we’ll learn what simple shifts and habits we can incorporate in our daily lives to support our body’s natural ability to recharge.
How We Make Energy
Every action, thought, heartbeat and process in our body is powered by energy made inside our cells. You might remember from biology class that this energy is created through a process called cellular respiration.
Most of this happens in the mitochondria, your cells’ microscopic power plants. Their job is to take food—glucose, fat, protein—and oxygen and turn it into ATP (adenosine triphosphate), our body’s energy currency. In simple terms, cellular respiration is the process by which cells break down glucose to produce energy.
There are Two Main Types of Cellular Respiration
Aerobic Respiration
Aerobic respiration takes place in the mitochondria and produces the most ATP from food and oxygen. This is the most efficient process and it happens when oxygen is available.
Anaerobic Respiration
When your cells need energy fast and oxygen is in short supply (like during intense exercise), they can also produce ATP without oxygen. This is called anaerobic respiration. It’s much less efficient and happens in the cell’s cytoplasm, producing less ATP and creating byproducts like lactic acid.
In everyday life, your body uses both types—mostly aerobic when you’re at rest or doing lighter activities and a mix of both when we push harder and our heart capacity reaches 80–90% of your MHR (Maximum Heart Rate).
Unless you’re a professional athlete or living at high altitudes where oxygen is scarce, your body will mostly rely on aerobic respiration to produce energy.
Perspective
Calories are the potential energy in your food and ATP is what that potential turns into once your body processes it. Every time you move, think or even breathe, you’re using ATP made from the calories you eat.
How Aerobic Respiration Works
This is how your body turns calories into energy. We’re about to get a little technical here, so geek out with me for a sec.
Glycolysis
Glucose is broken down in the cytoplasm into pyruvate—an organic molecule—making a small amount of ATP.
Pyruvate to Mitochondria
Pyruvate is transported into the mitochondria and converted to acetyl-CoA—acetyl coenzyme A, a metabolite important for energy production.
Krebs Cycle
Acetyl-CoA enters the Krebs cycle, releasing carbon dioxide—CO₂—and transferring high-energy electrons to carriers—vital coenzymes like NADH, FADH₂.
Electron Transport Chain
NADH and FADH₂ pass their electrons through the chain, generating lots of ATP which is basically a molecule with three phosphates that break apart to produce chemical energy.
Formation of Water
Oxygen accepts the electrons at the end of the chain, combining with protons to form water (H₂O).
Did you know?
Micronutrients don’t provide calories, but they are essential for turning food into energy. If you’re low on key vitamins and minerals—especially B vitamins, magnesium and iron—your body’s energy factories can’t work at full power and you’ll surely feel it. That’s why eating a variety of whole, unprocessed foods really does make a difference in your daily energy.
The steps above are happening right now as you read this line. If you eat enough food and breathe plenty of fresh air, your body efficiently produces 10 million energy molecules per second, leaving you feeling recharged, focused and fully alive. But when you lack micronutrients or spend your day in poorly aired rooms, your energy levels begin to drop. You’ll feel tired, run down and, with the time, might be plagued by chronic illnesses.
Perspective
If your phone charged as quickly as your cells make energy, it would jump from 0% to 100% in the blink of an eye, again and again, 24/7. Staying at 100% is a bit more complex, but for now, just know it all comes down to a balance between movement and recovery.
How We Store Energy
When energy demands are low, surplus is stored for later use, so your body can create ATP when needed.
There are two main storage forms
Short-Term Energy Storage: Glycogen
After immediate energy needs are met, excess glucose is stored as glycogen—first in the liver, then in muscles.
Glycogen is like your body’s ‘energy savings account’. It can be quickly converted back to glucose whenever you need it—such as during exercise or fasting.
Long-Term Energy Storage: Body Fat
When glycogen stores are full, any extra glucose (from overeating carbs or excess calories) is converted to fat (via de novo lipogenesis) and stored in fat cells (adipose tissue).
Fat is your most concentrated, long-term energy reserve. It can be broken down into fatty acids, sent to cells and burned for energy, especially during fasting, exercise or low-carb diets.
Energy storage is essential for everyday functioning. It influences how we sleep, focus, recover from illness and maintain overall well-being. However, excessive fat storage—especially when combined with a lack of regular movement—can lead to various health problems. These include insulin resistance, chronic inflammation and a higher risk of diseases like type 2 diabetes and heart disease. Too much stored fat can even interfere with your cells’ ability to produce and regenerate energy efficiently. This is a topic we’ll explore in future posts.
Survival energy bank
There is a third potential source of energy: amino acids from muscle protein. However, your body only taps into this ‘bank’ during starvation or certain medical conditions.
How We Use Energy
Now that you have a better grasp of how energy is produced, let’s look at how it’s used. Millions of processes happen in your body every second—from chemical reactions inside each cell, to nerve signals, to hormone release, blood flow and digestion—all working together to keep you alive and functioning. All of them have energy requirements, some more than others.
Your body is constantly burning energy even when you’re not moving.
This baseline energy needs is called your Basal Metabolic Rate (BMR).
BMR is the amount of energy your body uses at rest, just to keep your heart beating, your lungs breathing, your brain working and your organs functioning. For most people, BMR makes up to 70% of daily energy use.
On top of BMR, every activity you do—walking, thinking, exercising, digesting food, fighting off a cold—requires even more energy. Here’s a quick look at how different activities stack up.
Energy variables
This table reflects the average calories burned per activity type. To get an accurate caloric count, you must factor in age, sex, body weight and activity intensity among others.
As you can see, activities like running or cycling demand about 7x to 8x times your basal metabolic rate (BMR), meaning their energy requirements are far greater than simply being at rest. While the brain itself uses about 20% of your total energy, even intense cognitive work typically raises your BMR by only 10–20%.
So, why do we often feel exhausted after a long, stationary day at work?
We’ll go deeper into that question soon. But first—to better understand our modern energy struggles, let’s compare how we live today with how humans evolved to function.
How Our Ancestors Used Energy
Our energy needs have shifted dramatically over the ages, from the earliest Homo sapiens to hunter-gatherer societies tens of thousands of years ago, through the agricultural revolution, industrialization and into the modern era.
Our basic biology hasn’t changed much. But our habits, work, lifestyles and social connections are nothing like they were 50,000 years ago.
A Day in the Lives of our Ancestors
Back then, daily life meant moving, building, carrying and engaging with the world directly through our bodies. Today, appliances, computers, cars and a number of gadgets do most of the work for us. We can accomplish more in less time, but in the process, we’ve traded the richness of hands-on, physical experience for convenience.
This trade-off has also shaped our health and well-being in ways our ancestors never faced. In the past, movement was abundant, food was more nutrient-dense and real rest and recovery were built into the day. Now, we see more sitting, mental work, chronic stress, processed meals, less physical activity, and fewer opportunities for genuine rest. The routines that once supported vibrant health have been replaced by habits that often leave us depleted, distracted, or disconnected from our bodies.
Why We Still Feel Tired
Why do we often feel tired after a long, stationary day at work when the energy demands of cognitive work are relatively low? If this happens to you from mostly sitting and thinking, you haven’t actually burned up your physical energy stores. Instead, you’ve depleted some of your brain’s working resources. Meanwhile, your muscles’ energy (glycogen and fat) is still there, waiting to be used as soon as you move more.
Why We Feel Tired after Mental Work
Feeling tired after mental work is not the same as general fatigue—other factors are at play when you stand up from that chair and leave the office.
Neurotransmitter Depletion
Extended focus can use up chemical messengers, such as dopamine and serotonin, and the accumulation of glutamate, can lead to loss of motivation and mental power.
Emotional and Cognitive Stress
Stress, anxiety, multitasking, and being constantly ‘on’ drain your mental resources by overloading your attention and resilience.
Posture and Circulation
Sitting for hours reduces blood flow, oxygen delivery and can make you feel physically sluggish, causing inflammation and a number of other physical and mental challenges.
Disconnection from Natural Energy Cycles
Lack of movement, daylight, and varied stimulation can make it hard to feel alert or energized, even if you didn’t burn much energy.
Hydration, Nutrition & Breath
On certain busy days we tend to forget to refuel. Without the intake of proper food, regular and deep breathing and proper hydration feeling energized and getting through the day without breaking is impossible.
Poor Sleep
Poor sleep is often the accumulation and experience of the above points. Sleep is the only and most efficient way to regenerate. If we neglect it, we simply can’t be functional in life, no matter what else we do.
Perspective
You can feel deeply tired and depleted even if you used very little physical energy and that’s because your body and brain need more than just calories to feel alive.
What We Can Do
Here are simple every day habits that will help you recharge your brain and replenishing your body with energy.
1. Physical Movement
I need to move constantly to use the energy stored in my body and regulate my head. Walking, stretching or doing light exercise, even a couple of minutes make a huge difference. This increases dopamine, serotonin, endorphins and improves blood flow, helps regulate cortisol and supports neuroplasticity.
2. Sunlight & Natural Light
After moving from Baja California to Central Europe, I started to wake up early to catch as much sunlight as possible. Morning daylight helps increase serotonin production (converted to melatonin at night). Only 5–10 minutes of direct sunlight can positively affect mood and circadian rhythm. Vitamin D and light therapy are effective alternatives in low-light months.
3. Deep Breathing / Breathwork
I’m big on breathwork and pranayama. Here’s a quick tip: try regulating your breath with slow and long inhalations and exhalations. Five deep breaths can ground you and make you feel calmer and energized. This helps release GABA neurotransmitters and it lowers heart rate and activates the parasympathetic nervous system.
4. Hydration & Nutrition
I make sure to hydrate properly. Water is essential for brain function, neurotransmitter signalling and energy metabolism. Protein-rich snacks (nuts, yogurt, eggs), supply amino-acids needed to make neurotransmitters.
5. Social Interaction
A chat, a laugh, a meal together are important to me. Human bonding runs deep in our biology, shaping not just our mood, but our overall well-being. This boosts dopamine and oxytocin and enhances feelings of safety, reward and belonging.
6. Music or Creative Breaks
After a long stretch of brain-heavy work, I like to switch gears and do something creative, whether it’s for work or just for fun. It helps clear my head and get my energy back. This raises dopamine and serotonin.
7. The Power of a Nap
I was never into naps, until recently. But now, whenever I close my eyes for just 15–20 I feel more alert. Apparently, it has to do with acetylcholine, a brain chemical that gets restored while you sleep. I’ve also noticed that quick rest like this seems to ease some of the tension and stress I carry through the day.
Closing Thoughts
I will end today’s edition with three key things that will help you truly start working with your energy—not against it.
Practice More Self-Awareness: Become self-awareness of your energy patterns—what fuels your spark and what drains it. Meditation, journaling and self-reflection are some of the best tools.
Understand How Your Body Produces Energy: Get a basic understanding of how your body produces, stores and uses energy— including what supports that process and what gets in the way (like poor sleep, stress, or nutrient gaps). We did this in today. ☑️
Align With Your Own Biology: This requires a mindset shift from relying solely on willpower to aligning with your biology and the natural rhythms of life. Think of how our ancestors lived: more in sync with nature, movement, light and rest.
Today, we explored the foundational science behind physical energy—how your cells create and store fuel. We’re just getting started. In upcoming posts, we’ll go deeper into how your mind, emotions and relationships also shape your energy, and toolsets to support all of them.
What’s one small shift you want to try this week?
Leave a comment. I’d love to hear more about it.
It’s quite eye-opening to see how much humans used to move.