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What Is Carb Loading? Is It Useful & How?
Madhura MohanCarb loading is one of the most misunderstood nutrition strategies in sport. It is not an excuse to eat pasta the night before a 5K. It is a specific, scientifically-validated approach to maximising muscle glycogen before prolonged endurance events — and it only works under the right conditions.
What Is Carb Loading?
Carb loading (carbohydrate loading) is the practice of systematically increasing carbohydrate intake in the 1 to 3 days before an endurance event. The goal is to super-saturate muscle and liver glycogen stores above their normal capacity. Muscle glycogen is the primary fuel for sustained moderate-to-high intensity aerobic exercise. When glycogen runs out, performance drops sharply — the phenomenon runners call “hitting the wall.”
Who Benefits From Carb Loading?
- Endurance events lasting 90 minutes or more: Marathons, triathlons, long-distance cycling, half-marathons, team sports (football, rugby), long-course swimming
- High-intensity team sports: Where repeated sprints over 90+ minutes deplete glycogen
- NOT beneficial for: Events under 90 minutes, strength training, casual exercise, or short high-intensity events where phosphocreatine and anaerobic pathways dominate
How To Carb Load Correctly
Phase 1: Glycogen Depletion (optional)
Traditionally, carb loading was preceded by a depletion phase (high-intensity exhaustive exercise followed by very low carbohydrate intake for 3 to 4 days) to create a “supersaturation” effect. Modern research shows the depletion phase is largely unnecessary — simple carbohydrate loading without depletion produces similar glycogen supercompensation in trained athletes.
Phase 2: Loading Phase (1 to 3 days before event)
- Carbohydrate target: 8 to 12g per kg of bodyweight per day
- For a 70kg athlete: 560 to 840g carbohydrates daily
- Best foods: White rice, pasta, bread, potatoes, bananas, oats, sports drinks
- Avoid: High-fibre foods (bloating), fatty foods (slow gastric emptying), new foods (GI risk)
- Reduce training intensity: Rest or very light exercise during the loading phase
Race Day
3 to 4 hours before the event: 1 to 4g carbohydrates per kg bodyweight. Low fat, low fibre, familiar foods only. No experimentation on race day. Continue fuelling during the event (gels, sports drinks) for events over 90 minutes.
Expected Weight Gain
Each gram of glycogen is stored with approximately 3g of water. Full glycogen loading can add 1 to 2kg of body weight. This is expected and beneficial — it represents stored fuel, not fat. It will reverse within days after the event as glycogen is used.
Frequently Asked Questions
“Carb loading works. But only for the right event, with the right amount, at the right time. A pasta dinner the night before a 5K is not carb loading — it’s just dinner.”
90+ minute events only. 8–12g carbs/kg/day. 1–3 days pre-event. White rice, pasta, bread. Avoid fibre. Reduce training. Expect 1–2kg water weight. Fuel during the event too.