Carbs vs Fat for Energy: Which Fuel Source Powers Your Body Best?

Carbs or fat—which one fuels your body best? It’s a question that sparks more arguments than pineapple on pizza.

You’ve likely heard both sides. “Carbs are quick energy!” “Fat burns cleaner!” Meanwhile, you’re just wondering why you’re knackered by 3pm, even though you’re “eating healthy.”

The truth? Both low-fat and low-carb diets can help you lose weight. But the bigger question is—what makes sense for your body, your energy, and your long-term health?

Spoiler alert: your ancestors didn’t snack on bagels or guzzle seed oils. They ate what was available seasonally, and it wasn’t a cupboard full of refined carbs.

Let’s dig into how your body actually uses carbs and fat, and which fuel source really keeps you going.

TL;DR: Carbs vs Fat for Energy

• Carbohydrates give quick energy but spike blood sugar, leading to crashes, hunger, and fat storage.
• Fat provides stable, long-lasting energy, promotes fat oxidation, and keeps cravings in check.
• Our ancestors relied mainly on fat and protein, with carbs eaten seasonally, not every few hours.
• Modern diets packed with refined carbohydrates, added sugars, and vegetable oils drive today’s health problems.
• To boost fat loss, body composition, and overall health, eat real fat and use carbs strategically, not constantly.

How the Body Uses Energy: Carbs vs Fat Explained

Before taking sides in the carbs vs. fat for energy debate, we need to understand how the human body actually works when it comes to fuel.

Think of your body like a hybrid car. It can run on two primary fuel sources: carbohydrates and fat. Both provide energy, but in very different ways.

Carbohydrates: The Fast Fuel

When you eat carbs—whether it’s fruit, rice, or a chocolate bar—your body breaks them down into glucose. That glucose enters the bloodstream, becoming blood sugar, which your body uses immediately for energy or stores for later.

Some of it gets stored in your muscle glycogen stores and liver for quick access. But if you’ve got more carbs than your body needs right now? That excess is converted into body fat.

This makes carbs great for quick energy, especially during high-intensity exercise, where fast fuel is needed. But there’s a catch: that energy doesn’t last long. When blood sugar drops (and it will), so does your energy, mood, and sometimes your will to live.

Fat: The Endurance Engine

Fat, on the other hand, is the slow-burn fuel. It doesn’t spike your blood glucose or crash your energy levels. Instead, your body taps into fatty acids—either from your food or your stored fat—and converts them into energy through fat oxidation.

Fat is the preferred fuel for low-intensity and endurance exercise, as well as for getting through the day without needing a snack every two hours. It’s steady, reliable, and efficient.

Your body’s ability to tap into this fat-burning mode depends on your carbohydrate intake and how metabolically flexible you are. If you’re constantly loading up on sugar and starch, your body gets lazy and forgets how to burn fat effectively.

That’s why many people feel like they “hit a wall” if they miss a meal—it’s not normal hunger. It’s blood sugar withdrawal.

So… Which Fuel Should You Use?

Here’s the kicker: your body will always burn carbs first when both are available. It’s quicker, easier, and requires less work. But that doesn’t make it better.

Relying solely on carbs means you’re constantly topping up your glycogen stores, continually spiking and crashing blood sugar, and storing excess calories as fat when your body doesn’t need the immediate energy.

But when you lower your carb diet and shift towards fat metabolism, you teach your body to tap into the massive fat supplies it already has—something your ancestors would have depended on to survive.

Up next: let’s break down the pros and cons of low—fat and low—carb diets and why both have their place, but only one makes long-term sense.

A Look at Low-Fat Diets: What Works and What Doesn’t

The low-fat craze didn’t happen by accident. For decades, we were told that eating fat, especially saturated fat, clogged arteries and caused heart disease. So, we stripped it from our diets, replaced it with more carbohydrates, and poured vegetable oils into everything from margarine to muffins.

At first, people lost weight. Why? Because they were cutting total calories—not because dietary fat was the villain. Fat has more calories per gram than carbs or protein, so dropping it often creates a caloric deficit.

That part makes sense. But what we didn’t realize was how that shift affected our blood sugar, hormones, and even body composition.

The Downsides of Low Fat

Low-fat diets often mean high carbohydrate intake. Especially the processed kind, which consists of refined carbohydrates and added sugars. These spike blood glucose, crash your energy, and push your body into fat storage mode over time.

Without enough fat, your body struggles to synthesize hormones, keep your brain sharp, or even supply energy between meals. You’re running on quick fuel, burning through it fast, and are constantly hungry.

Plus, when fat supplies are limited and your glycogen stores run dry, guess what your body turns to next? Amino acids—from your muscles. That’s right: you could be breaking down muscle for fuel just because your diet lacks what it actually needs.

The Role of “Healthy Fats” in a Healthy Diet

Here’s where things get twisted: while we were avoiding natural fats like tallow and butter, we were being encouraged to eat polyunsaturated fats from seed oils—aka vegetable oils.

These are fragile, oxidize easily, and do your overall health no favors. In fact, the rise in trans fats and seed oils has coincided with a sharp increase in obesity, diabetes, and metabolic issues.

Our daily intake of these industrial oils is higher than ever, yet we’re more fatigued, inflamed, and hormonally out of balance.

Coincidence? Doesn’t look like it.

Low-Carb Diets: Shortcuts to Fat Burning or Long-Term Solution?

Low-carb diets took the spotlight for one big reason: they work. When you reduce carbohydrates, your body switches gears. It starts tapping into fatty acids and stored fat for fuel—a process called fat oxidation. That’s where the magic happens.

This shift doesn’t just help people lose weight. It stabilizes blood sugar, lowers insulin levels, and keeps energy levels steady throughout the day. You don’t get that mid-afternoon crash or the “hangry” mood swings.

And unlike carbs, fat is satiating. Meals keep you full for hours. You’re not raiding the fridge an hour after lunch or dreaming about snacks during meetings.

You eat, you’re satisfied, and you get on with your day.

What Happens Inside the Body

When you eat fewer carbs, your glycogen stores start to deplete. Once they’re low, your body produces ketones from fatty acids—an alternative energy source that your brain and muscles can run on just fine – in fact, it feels great.

This metabolic shift improves the body’s ability to burn fat for fuel and makes it more efficient at managing blood glucose. Over time, it even boosts fat metabolism, which is a fancy way of saying your body becomes better at using its own fat supplies to provide energy.

That’s why so many people on low-carb or ketogenic diets experience better focus, fewer cravings, and even improved well-being. You’re no longer at the mercy of your next carb fix.

What to Watch Out For

That said, going low-carb doesn’t give you a free pass to eat just anything labeled “keto.” Packaged low-carb junk still contains vegetable oils and trans fats, often lacking nutritional value.

Also, during high-intensity exercise, your muscle glycogen stores matter. If you’re lifting heavy or sprinting, your body might need additional carbs now and then to fuel exercise efficiently.

Most of us aren’t training like endurance athletes, but this balance becomes more important if you are.

In general, though, for the average adult aiming for fat loss, stable energy, and improved overall health, a low-carb approach just makes sense—especially when it’s based around real, ancestral foods rather than modern ultra-processed substitutes.

What Our Ancestors Ate (And What That Tells Us Today)

Let’s rewind the clock. Imagine your ancestors out in the wild, long before convenience stores, food delivery, or 24/7 cereal ads. What did they eat? Well, it depended on the season—and more importantly, what was available.

Carbohydrates weren’t a constant. They came from natural sources like fruit, honey, and the odd starchy root—but only when those foods were in season. If the fruit trees weren’t ripe, you didn’t eat fruit. Simple as that.

The rest of the year? Your body ran on fat from animals. Not just muscle meat, but the fatty acids found in fat, organs, marrow, and connective tissue. This wasn’t optional. It was survival.

And because there was no fridge, no granola bars, and no refined carbohydrates, our ancestors became excellent at switching between glycogen stores when food was plentiful and fat oxidation when it wasn’t.

That’s metabolic flexibility—the very thing many people today have lost.

The Common-Sense Diet

Now think about what we’re eating today. Pasta, cereal, snack bars, soda, muffins, white bread, crisps… all packed with added sugars, vegetable oils, and empty calories.

Would it make sense to expect the human body, designed over hundreds of thousands of years to thrive on meat and seasonal produce, to be perfectly fine with modern food made in a factory?

Of course not.

That mismatch is a big reason we’re dealing with metabolic syndrome, weight gain, low energy, and chronic fatigue. Our body can’t keep up with the barrage of more carbs, seed oils, and ultra-processed nonsense.

The Problem with Modern Carbohydrates

Carbs like fruit, honey, and vegetables were once occasional, natural foods. Today, modern refined carbohydrates, stripped of fibre and loaded with added sugars, flood the diet—and our bodies can’t keep up.

The result? Wild blood sugar spikes, crashes, constant cravings, and a metabolic system that’s under siege.

Fat Took the Blame

While carbs crept into everything, fat—especially saturated fat—was wrongly demonized. Natural dietary fat became the villain, while vegetable oils and carb-heavy low-fat products took over.

Real fat doesn’t spike blood glucose or trigger fat storage like modern carbs do. Meanwhile, seed oils and trans fats set the stage for inflammation and declining general health.

The Vicious Carb Cycle

The more carbohydrates we eat, the hungrier we get. Carbs burn fast, leading to endless snacking, cravings, and more fat stored instead of burned. It’s a vicious cycle—and it all starts with modern food.

Fat as Fuel: A Smarter, Simpler Approach

Animal fat wasn’t feared for most of human history—it was survival fuel. Calorie-dense, stable, and slow-burning, fat kept our ancestors alive when food was scarce.

Unlike carbs, fat doesn’t spike blood sugar or crash your energy. It promotes fat oxidation, allowing your body to tap into massive fat supplies for long-lasting, stable energy.

There’s a reason our bodies have a fat storage system; it’s good stuff that can be used later in times of famine. It’s a survival tool.

More Than Just Energy

Fat doesn’t just supply energy—it builds hormones, brain cells, and supports immune function. Without enough, your body struggles on every level, from libido to metabolism.

When eaten in a diet free from refined carbohydrates and added sugars, real fat becomes one of the most powerful tools for improving body composition, boosting fat loss, and supporting long-term well-being.

Finding the Right Balance: A Nutritional Approach That Works

Here’s the truth most diet books won’t tell you—no single, perfect ratio of carbohydrates, fat, and protein works for everyone. We all have different genes, health histories, stress loads, and levels of physical activity.

But some patterns seem to hold true for most people:

🍞 Most of us eat way too many refined carbohydrates
🧈 Most of us eat too little real (animal) fat
🍗 Most of us don’t get enough protein or quality amino acids
🤔 And most of us have no idea how much better we could feel if we gave our body the fuel it was designed to run on

Paul Saladino and Andrew Huberman say it well here…

The Missing Link: Protein and Fat

When you eat enough protein and fat, your appetite naturally regulates. You don’t need to count calories, white-knuckle cravings, or obsess over macros. You just eat until you’re full, and stay full for hours.

Fat and protein provide the amino acids, vitamins, and minerals your body needs to build, repair, and thrive. They support hormone synthesis, fat metabolism, immune function, brain health, and steady energy.

If you’re still afraid of total fat intake, it might be time to challenge that.

Focusing on real fat—from meat, eggs, butter, tallow, and other ancestral sources—is a far cry from the polyunsaturated fats and trans fats hiding in processed food.

The Carb Curve

If you’re metabolically healthy, lean, and active, you may handle more carbs just fine, especially if they come from whole, seasonal foods like fruit, roots, or raw honey.

These can be used strategically, especially around endurance exercise or when muscle glycogen stores need replenishing.

But if you’re dealing with health issues, fatigue, weight gain, brain fog, or blood sugar swings, cutting back on carbs—especially added sugars and modern processed junk food—can make a huge difference.

You don’t need to go zero carb forever.

However, reducing carbohydrate intake and relying more on fat as your primary fuel source allows your body to rebalance. It’s not a punishment—it’s just common sense.

My Experience: From Chronic Fatigue to Fat-Adapted

For me, this wasn’t just theory—it was personal. I didn’t start questioning the whole carbs vs fat for energy debate until my body completely gave up on me.

I was living in a constant fog. No energy, no drive, barely enough strength to get through the day.

I was doing everything the experts said—eating “balanced,” watching my calories, avoiding animal fat & red meat, and topping up with healthy snacks (aka more carbohydrates) every couple of hours.

Sound familiar?

Then came the diagnosis: chronic fatigue syndrome. But labels don’t fix anything. What helped was stepping back and asking: what would my ancestors have eaten if they were trying to survive and function at their best?

Spoiler: it wasn’t toast and orange juice.

Cutting the Carbs—and the Crashes

Out of desperation, I stripped it all back. I cut out all carbohydrates—even the so-called healthy ones like fruit and starchy veg. Not forever… to see what would happen.

The change was wild. My energy started coming back. My mind felt sharper. My body stopped begging for snacks and sugar every few hours. It was as if I’d finally stopped fighting with my metabolism and started working with it.

That was the start of learning how to fuel myself properly—with real fat, enough protein, and zero tolerance for junk food.

What I’ve Learned

These days, I can tolerate small amounts of carbohydrates—seasonal fruit, a bit of honey, maybe some root veg here and there. But if I push it too far, those old symptoms creep back in.

That tells me my body’s ability to process sugar isn’t what it used to be. Maybe it’s still healing. Or maybe modern food broke it permanently. Either way, I’ve learned to listen to what my body actually needs: steady fuel, not sugar spikes.

And what fuels me best, without fail, is fat.

The Verdict on Carbs vs Fat for Energy

Choosing the right fuel source isn’t about following the latest diet—it’s about understanding what your body is designed to run on.

Yes, carbohydrates can provide energy, especially during intense bursts. But for daily life, stable focus, and lasting energy, fat is the better bet.

Your ancestors weren’t eating six meals daily or carb-loading at every opportunity. They thrived on real fat, protein, and seasonal foods—and so can you.

What This Means for You

If you’re tired, gaining weight, or battling cravings, odds are your carbohydrate intake is higher than your body can handle… you’re not fueling your body right.

Shifting to real fat and cutting out added sugars and vegetable oils allows your body to reset, heal, and tap into its natural fat-burning engine.

And if that also means better moods, fewer crashes, and more effortless fat loss—even better.

Fuel Like a Human

Ditch the food pyramid. Eat real food. Prioritise fat and protein. Use carbs intentionally, not constantly. I call this the Ultimate Human Diet.

And when in doubt, ask:

Would this food have existed 10,000 years ago?

If not, it probably doesn’t belong in your diet today.

And that’s it… have a nutritious day!

FAQs

Are carbs or fats better for energy?

Carbohydrates are good for quick bursts of energy, but fat is better for steady, long-lasting fuel. Fat stabilizes blood sugar and hunger, making it a better daily fuel source for most people.

Is it better to eat carbs or fat for working out?

For high-intensity exercise, carbohydrates help top up muscle glycogen stores. But for regular or low intensity training, eating more fat works great and keeps your energy stable without the crashes.

Is it better to burn carbs or fat?

Burning fat is better for long-term health, fat loss, and steady energy. Burning carbs is helpful for quick energy but leaves you more prone to hunger, cravings, and blood sugar dips.

Does it take more energy to burn fat or carbs?

Yes, burning fat takes more work than burning carbs. But that’s a good thing—it keeps energy steady and taps into your body’s ample fat supplies without the ups and downs of blood glucose spikes.