As a sports nutritionist, I often hear active people - from weekend warriors to serious competitors - say the same thing:
“Something must be wrong with my diet… I’m just not getting what I want out of my training.”
Nine times out of ten, what’s wrong isn’t their effort - it’s their fuelling.
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Below are three of the most common fuelling mistakes that quietly hold athletes back. Whether you’re training for a race, playing team sport, or just wanting more from your workouts, avoiding these errors can make a huge difference to how you feel and perform.
Error 1: Exercising on an Empty Stomach
Somewhere along the line, the myth took hold that eating before exercise slows you down or makes you sluggish. As a result, plenty of exercisers - even competitive athletes - go out of their way to train fasted, often avoiding food for three or four hours beforehand.
The truth? You’ll perform better when you’re fuelled, not fasted.
Think of it like this: you wouldn’t expect your car to run well without fuel in the tank. Your body works the same way - first put fuel in your car, then go.
What the Research Shows
In one study, seven cyclists completed two workouts at 70% VO₂max until exhaustion.
- On one occasion, they ate a 400-calorie breakfast three hours beforehand.
- On the other, they skipped breakfast and only ate dinner the night before.
When fasted, they lasted 109 minutes. After breakfast, 136 minutes - almost half an hour longer.
That’s a big difference for something as simple as eating beforehand.
Bottom line: if you want more stamina and endurance, don’t train on fumes.
Cyclists who ate breakfast before training lasted nearly 30 minutes longer than when fasted - proof that fuelling before exercise boosts endurance.
A balanced pre-exercise meal or snack, rich in carbs, moderate in protein, low in fat, gives your body the energy to perform at its best.
READ ALSO: Should I Skip Breakfast to Train Fasted?
Error 2: Skipping Fluids During Short Workouts
Many exercisers assume they don’t need to drink anything during sessions lasting less than an hour. “I’m only training for 45 minutes - I’ll be fine,” they say.
Not quite. Even mild dehydration can affect performance, especially when the session is intense or in warm conditions.
The Evidence
- When cyclists replaced sweat losses with plenty of water (≈1.4 L), their sprint performance improved 6% over baseline.
- When they consumed 300 calories of sports drink during the ride, they improved 12%.
That’s a massive difference - the kind that separates first place from the middle of the pack.
Practical takeaway: even for shorter sessions, sip regularly.
Water is fine, but for hard efforts or competition, small amounts of a carbohydrate-electrolyte drink can provide a performance edge. Sports drinks, gels, flat cola, or even boiled sweets can do the job.
Error 3: Dieting Too Hard to “Get Lean”
Many athletes (and plenty of regular gym-goers) believe they’d perform better if they could just lose those “last few kilos.” And yes, reducing excess body fat can improve relative power and efficiency.
But when you start under-eating to chase a “perfect” body composition, performance usually goes the other way.
Aggressive dieting may improve power-to-weight ratio in the short term, but under-fuelling leads to fatigue, nutrient loss, and poor long-term performance.
When you cut calories too aggressively, you’re also cutting:
- Carbohydrates - your muscles’ and brain’s preferred fuel.
- Protein - needed for muscle repair and recovery.
- Vitamins and minerals - essential for energy metabolism and immune health.
You can’t expect to train longer or harder on too little fuel.
Furthermore, if it takes severe restriction to lose weight, it’s unlikely you’ll keep it off once you resume eating normally.
READ ALSO: Should you be hungry when losing weight?
A Reality Check
Weight is about far more than willpower - genetics matter.
If you’re already leaner than most of your family, your body might resist getting much leaner.
Rather than forcing it, shift your focus to performance. That is to say, fuelling properly, training smart, and recovering well. Your body will find the weight that suits your physiology and your sport.
There’s no scientific evidence that the leanest athlete is the best athlete.
But there’s plenty showing that well-fuelled athletes perform better, recover faster, and stay healthier.
Under-fuelling makes training feel harder, limits recovery, and can shift focus from performance to appearance. Fuel first = perform better.
Final Thoughts
If your training feels harder than it should, don’t automatically blame your program - look at your fuelling.
Ask yourself:
Because the truth is simple:
You can’t expect to train or compete at your best if you’re under-fuelled.
Eat well. Drink smart. Fuel to perform - not just to get by.
READ ALSO: Fuelling up before exercise
