Carb Loading: What It Actually Means — and What It Doesn't
- Shrey Aggarwal
- Mar 27
- 5 min read
I've had this conversation more times than I can count.
An athlete tells me they carb-loaded before their big race or match. I ask what they did. "Had a big bowl of pasta the night before."
That's not carb loading. That's just dinner.
The confusion around this one term is doing real damage to how athletes prepare for competition. Some do it wrong and wonder why it didn't help. Others do it when they don't even need it. And many avoid carbs entirely before competition because they're worried about feeling heavy — which is almost the opposite of what the science recommends.
Let's clear it up properly.
This blog contains
What Glycogen Actually Is and Why It Matters
When you eat carbohydrates, your body stores the excess as glycogen — primarily in your muscles and liver. Muscle glycogen is your body's most accessible, high-powered fuel source during exercise. The harder and longer you go, the more you rely on it.
The problem is storage is limited. Research shows that by the 90–120 minute mark of sustained effort, glycogen stores can be critically low — and when they are, performance drops sharply. Speed falls, effort perception climbs, and your ability to sustain intensity collapses.
This is what athletes call "hitting the wall". It's not fitness. It's fuel.
Carb loading exists to push that ceiling — to start competition with glycogen stores maximised above normal resting levels, giving you more runway before depletion becomes a problem.
Where the Myth Came From
The original carb loading protocol was developed by Scandinavian researchers in the 1960s. Athletes spent three days depleting glycogen through low-carb eating and exhausting training, followed by three days of extremely high carbohydrate intake. The idea was that the depletion phase would prime muscles to store even more glycogen — a process called "glycogen supercompensation"
It worked, but it was miserable. Three days of carb restriction left athletes fatigued and flat right before competition.
Later research showed the depletion phase wasn't necessary at all. Well-trained athletes could achieve the same glycogen supercompensation simply by combining a training taper with a high carbohydrate diet over three to four days. No depletion needed. This is the modern protocol — and it still looks nothing like one pasta dinner.
What Carb Loading Actually Requires
True carb loading is a structured 36–48 hour process. Sports nutrition guidelines put the target at 10–12g of carbohydrate per kg of body weight per day during the loading window — combined with a significant reduction in training.
In real numbers: a 70kg runner needs 700–840g of carbohydrates per day. That's rice at every meal, bread, potatoes, fruit, and likely liquid carbohydrate sources too. It requires deliberate, structured eating across the full day for at least two days.
One thing worth knowing: for every gram of glycogen stored, the body retains approximately 2.7g of water. Athletes will gain 1–2kg during a proper carb load. This is not fat. It is water bound to stored fuel. Athletes who understand this welcome it. Those who don't, panic unnecessarily.
Who It's Actually For and Who It Isn't
This is the most misunderstood part.
Carb loading is evidence-based for one specific context: events lasting longer than 90 minutes at sustained moderate to high intensity. Research consistently shows that elevated glycogen stores postpone fatigue by approximately 20% and improve performance over a set distance by 2–3%. For a marathon runner, that's real, measurable minutes.
So it's genuinely useful for marathon runners, long-course triathletes, and cyclists in road races.
For a 5km runner? Research is clear — there is no performance benefit for efforts under 90 minutes. Glycogen at normal resting levels is more than enough. You won't run faster because you ate more pasta.
For a cricketer, it depends on format and role. A fast bowler in a Test match — bowling 20+ overs across multiple days with repeated explosive efforts and accumulated fatigue — has genuine glycogen demands. But the solution is consistent daily carbohydrate intake structured across the match, not a loading dinner the night before. A T20 batter has entirely different requirements. One approach does not fit all.
For a gym-goer training 45–60 minutes three times a week? Carb loading will not help. It may just cause unnecessary weight fluctuation and digestive discomfort.
What Actually Matters for Most Athletes
Here's what the carb loading conversation misses for the majority of active people: the bigger issue isn't loading before competition. It's chronic daily under-fuelling throughout the training week.
Most athletes I work with aren't going into competition low on glycogen because they forgot to carb load. They're going in low because they've been under-eating carbohydrates for weeks. They've absorbed the low-carb messaging everywhere on social media. They feel guilty about rice. They skip the post-training meal because they're not immediately hungry.
Week after week, glycogen stores are partially depleted. Training sessions are harder than they should be. Recovery slows. Adaptation suffers. That is a carbohydrate availability problem — and it doesn't get fixed by one loading dinner. It gets fixed by understanding your daily carbohydrate needs relative to your training load and structuring nutrition consistently around that.
This is what carbohydrate periodisation actually means — matching intake to the demands of each day. Higher on hard training and competition days. Lower on rest days. Not restriction. Purposeful, structured fuelling.
The Fueletics Perspective
At Fueletics, carbohydrate strategy comes down to one question: what does this athlete actually need, on this day, for this session or event?
For a marathon runner, yes — a proper 36–48 hour carb load with specific gram-per-kg targets is part of the race-week plan. For a cricketer, it's consistent daily carbohydrate intake structured around match demands and recovery windows. For most people training three to five days a week, the focus is ensuring day-to-day carbohydrate intake is actually adequate for the work being done — which for the majority, it isn't.
Carb loading is real and evidence-based. But it has a specific context, a specific protocol, and a specific athlete it was designed for. Outside of that, the most powerful carbohydrate intervention is simply eating enough of them — consistently, strategically, and without the guilt that low-carb culture has created around one of sport's most important fuels.
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**Research References**
Bergstrom & Hultman — Muscle Glycogen Synthesis After Exercise. Acta Medica Scandinavica, 1967.
Hawley et al. — Carbohydrate-Loading and Exercise Performance: An Update. Sports Medicine, 1997.
Burke LM et al. — Carbohydrates for Training and Competition. Journal of Sports Sciences, 2011.
Thomas DT et al. — Position of the Academy of Nutrition and Dietetics: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics, 2016.
Gatorade Sports Science Institute — Dietary Carbohydrate and the Endurance Athlete: Contemporary Perspectives.
PMC Review — Carbohydrate Supplementation Approaches in Elite Long-Distance Endurance. Nutrients, 2025.
ScienceDirect — Carbohydrate Loading Overview.