Despite decades of research, carbs remain the most argued-over macronutrient in athletic performance, here's what the science settles.
Despite decades of research, carbs remain the most argued-over macronutrient in athletic performance, here's what the science settles.
Somewhere between the low-carb movement and the protein obsession, carbohydrates became the nutrient everyone has an opinion about and almost nobody understands properly.
That's not an exaggeration. Walk into any gym, sit in any changing room before a match, scroll through any athlete's comment section, the noise around carbohydrates is louder than ever, and most of it points in the wrong direction. Too much. Too little. Wrong type. Wrong time. The confusion isn't random; it's the product of diet culture bleeding into sport, where the rules are fundamentally different.
In everyday life, carbohydrates are often framed as optional, something to moderate, swap out, or earn. In sport, that framing collapses. Carbohydrates are the primary fuel for high-intensity work. Muscle glycogen, the stored form of glucose, is what powers a sprint, a tackle, a heavy squat, a final set. When it runs low, output drops. Not because of willpower or fitness, but because the engine is running on fumes.
Fat can sustain low-intensity effort. Protein can contribute under extreme conditions. But neither can replace carbohydrate's role when intensity climbs. This isn't a preference, it's physiology. The body's reliance on glycogen during hard exercise is well established, and no amount of metabolic adaptation fully overrides it for athletes training and competing at meaningful intensities.
Most athletes who think they're eating enough carbohydrates are eating them at the wrong time. A large pasta dinner the night before a session doesn't compensate for arriving at training with depleted glycogen. What you eat in the hours before, and in the window after, matters as much as total daily intake.
Pre-exercise carbohydrates prime the system. Intra-exercise carbohydrates, gels, drinks, chews, sustain it during sessions lasting longer than an hour. Post-exercise carbohydrates begin the process of restoring what was used. Each of these windows has a different purpose, and treating them as interchangeable is one of the most common errors athletes make. Eating more at dinner doesn't fix what was missing at 6am.
The other persistent mistake is treating carbohydrate requirements as fixed. They aren't. A rugby prop in pre-season double sessions has different needs from a marathon runner in a taper week, who has different needs again from a recreational gym-goer training four times a week. Body mass, training volume, session intensity, sport type, and even the time of year all shift the numbers.
Custom nutrition, genuinely tailored to what an individual is actually doing, exists precisely because generic recommendations fall short. The athlete who follows a standard carbohydrate guideline without adjusting for their specific load is either under-fuelling or carrying unnecessary intake. Neither is optimal.
The cultural baggage around carbohydrates, the idea that they cause weight gain, that they're somehow less clean than other macronutrients, that elite athletes are quietly avoiding them, has real consequences. Athletes under-fuel. Recovery suffers. Training quality drops. And because the decline is gradual, it often gets misattributed to overtraining, poor sleep, or motivation.
Carbohydrates don't need defending. They need understanding. Not as a dietary villain or a magic bullet, but as a functional fuel with specific roles, specific timing requirements, and specific quantities that vary from one athlete to the next.
Getting that right isn't complicated once the noise clears. It just requires looking at what you're actually doing, when you're doing it, and fuelling accordingly, rather than borrowing a framework designed for someone with entirely different demands.