Fuel Smarter, Run Stronger
The right carbs at the right time keep you steady from start to finish
Every runner knows the feeling of running out of gas.
One minute you’re cruising, the next your legs turn to concrete, your breathing spikes, your head gets foggy, and every step feels like a battle just to keep moving. That crash isn’t about fitness — it’s about energy.
Your body can only go so far on what it has stored, and once those reserves run low, performance nosedives. No matter how much willpower you have, you slow down because the engine is out of readily available fuel.
That’s why fueling matters. Getting the right carbs at the right time can mean the difference between fading halfway through and finishing strong. But fueling is more than grabbing a random gel or sports drink on race day. It’s about understanding how fuel works, what your body actually needs, and how to train your gut to handle it.
Some runners overcomplicate this — chasing exotic products or obsessing over every gram. Others under-fuel, hoping grit will carry them through. Both approaches miss the point. Smart fueling means matching the fuel to the run.
In this article, we’ll break down why we fuel in the first place, how to choose between gels, chews, drinks, or real food, and how to time your intake so your energy stays steady from start to finish. Fuel smarter, and your training clicks, your racing feels smoother, and you finally unlock the full payoff from the fitness you’ve built.
“An army marches on its stomach.” – Napoleon Bonaparte
👉 Ready to fuel smarter and run stronger? Book your FREE discovery call and let’s build a race-day strategy that works for you.
Why We Fuel at All
Running is about more than just muscles and lungs — it’s about energy management.
At every pace, your body pulls from three fuel sources:
Fat – plentiful, but slow to turn into usable energy.
Blood sugar – a small, quick supply from what you ate recently or what you take in mid-run.
Glycogen – stored in your muscles and liver, very fast to tap into, but limited.
At easy paces, fat can cover most of the need, with a little help from blood sugar and glycogen. But as you speed up, fat can’t keep up — it’s too slow to process and requires plenty of oxygen. That’s when glycogen and blood sugar take over. The higher the intensity (and the less oxygen available to process fat), the more your body leans on those quick fuels.
Here’s the catch: glycogen is the only fuel your body can store in large amounts inside muscle and break down fast enough to sustain high intensity when oxygen is limited. Blood sugar contributes, and can also be used quickly, but the supply is smaller and can’t cover the demand as quickly since it’s spread through your body.
Over time, glycogen gets used up. If your effort is low enough, fat and blood sugar can cover more of the need and help conserve glycogen. But when intensity stays high, there’s no fuel source fast enough to fill the gaps. Eventually, glycogen runs too low, and that’s when you hit “the wall.”
Legs turn heavy — stride shortens, cadence drops.
Breathing spikes — the same pace suddenly feels like a sprint.
Head goes foggy — focus slips, decisions get clumsy, even holding form feels confusing.
Temperature regulation suffers — sweat rate shifts, you may feel chills or overheating as your system strains to keep up.
Mood tanks — frustration, irritability, or an urge to quit out of nowhere.
Energy collapses — one moment you’re running, the next every step feels like a grind.
This isn’t about mental toughness. It’s physiology — it’s your body pulling the brakes.
Fueling on the run works best when effort is sustainable. Extra blood sugar helps stretch your glycogen stores and keeps your energy systems in balance. It won’t override pacing or oxygen limits — but it will help you stay steadier and stronger for longer.
What Makes a Good Fuel
The best run fuel is one your body can absorb quickly, burn efficiently, and stomach without discomfort. That’s why nearly all endurance fuels are built around carbohydrates — but not all carbs act the same.
Your muscles only run on glucose. Every carb you take in — from gels, drinks, or real food — has to be broken down into glucose before it can actually fuel your stride. The difference between sugar types is how fast they become glucose and how well your gut can handle them.
Here’s the breakdown:
Single sugars (monosaccharides) – fastest to absorb
Glucose: the body’s preferred fuel. Goes straight into the bloodstream and to your muscles.
Fructose: absorbed through a separate pathway. Slower on its own, but when paired with glucose it increases total carb absorption per hour.
Galactose: less common in sports fueling, from milk sugars. Slower and less efficient than glucose.
Double sugars (disaccharides) – pairs of singles, must be split first
Sucrose (table sugar/candy): one glucose + one fructose. Breaks apart quickly, so it uses both absorption pathways. A common and effective sports fuel.
Lactose: glucose + galactose. Breaks down slowly and often causes GI distress — not a good fueling choice.
Maltose: two glucose units. Splits into glucose quickly, similar in effect to maltodextrin.
Chains (oligosaccharides / polysaccharides) – longer chains, need more steps to break down
Maltodextrin: short chains of glucose. Technically a complex carb, but digests almost as fast as glucose. Widely used in gels and drinks because it’s easy on the stomach and less sweet.
Starches (rice, potatoes, oats): long chains of glucose. Slower to break down, better for lower-intensity or ultra-distance efforts where comfort and variety matter more than speed.
What this means for runners:
Glucose is fastest, but the gut has a limit.
Pairing glucose with fructose (or sucrose, which is both) lets you absorb more per hour.
Maltodextrin smooths things out — quick like glucose, but easier to tolerate in large amounts.
Real-food starches can work at low intensity, but are not good at race pace.
That’s why sports fuels often mix glucose + fructose + maltodextrin: it maximizes absorption, minimizes gut stress, and delivers energy quickly enough to match the effort.
Good mid-run fuel should also be:
Low fiber, fat, and protein — to avoid slowing digestion.
Portable and repeatable — something you can take in stride and your stomach can trust.
Don’t just rely on the label. Different brands use different sugar blends, and every stomach reacts differently. Check the ingredients, practice with them in training, and never gamble on something new on race day.
In general, you’ll pay more for higher-quality blends that use balanced sugars and gut-friendly ingredients — but for many runners, that cost is worth it when the alternative is stomach trouble at mile 18.
Timing and Practice
Fueling isn’t just about what you take — it’s about when you take it and how you practice it. The right timing can be the difference between steady energy and running out of gas.
How much:
Most runners do well with 25–60 grams of carbohydrate per hour (about 100–240 calories) once the run goes longer than an hour. That might look like a gel every 30–40 minutes, a handful of chews spaced across a couple of miles, or steady sipping from a sports drink.
When to start:
Fueling doesn’t just begin once you’re already out the door — it starts with what you do before the run. Going in topped up makes a big difference. A carb-rich meal the night before and a light snack an hour or two before you start can give you a head start on glycogen and blood sugar.
Once you’re moving, don’t wait until you feel drained. By the time you feel heavy or foggy, it’s too late to catch up. Instead, begin fueling early — usually in the first 30–45 minutes of a long run or race — and then keep a steady rhythm the rest of the way.
How often:
It’s not just how much you take in, but how you spread it out. Your body absorbs fuel better when it comes in steady intervals instead of all at once. Smaller, regular doses are easier on your stomach and keep energy more level. Think of it as a rhythm: frequent sips or bites that fit naturally into your run, rather than big gaps followed by big dumps.
Match your effort:
Fueling gives the most benefit when the pace is steady and sustainable. At half-marathon or marathon intensity, it can be the difference between holding form deep into the race and fading hard. At sprint intensity, though, no fuel can keep up — oxygen is the limiter. Use fueling to extend endurance, not to save an all-out effort.
Practice in training:
Fueling isn’t something to leave for race day. Your stomach adapts to carbs just like your muscles adapt to mileage. If you never practice, you’re more likely to deal with bloating or gut distress when it matters most. Long runs are your testing ground — try different fuels, play with timing, and find the amounts your system can handle comfortably. By race day, fueling should feel automatic, not experimental.
What’s your go-to mid-run fuel? Drop it in the comments — gels, chews, drinks, or something offbeat — and let’s compare what actually works in the real world.
At the end of the day, fueling isn’t about magic formulas or trendy products. It’s about giving your body the energy it needs to actually use the fitness you’ve worked so hard to build.
Get the basics right — understand your three primary fuels and how intensity affects them, choose carbs that your body can absorb, and practice timing your training. Do that, and fueling shifts from something to stress about into a reliable part of your running toolbox.
Ready to put this into practice? On your next long run, test one fueling strategy — timing, type, or amount — and see how it changes your energy.