Triathlon combines three demanding disciplines into one race - swim, bike, run. Whether you're doing a sprint, Olympic, or half-iron distance, what you eat before the race directly affects how you perform across all three legs.
The unique challenge of triathlon is that different disciplines have different GI demands. Swimming with a full stomach is uncomfortable. The bike allows easier digestion. The run is notorious for causing GI distress. Your pre-race nutrition needs to set you up for success across all three.
Here's the evidence-based approach to fuelling your triathlon, whatever the distance.
Distance Matters
Pre-race nutrition scales with race duration:
- Sprint (750m/20km/5km): 45-75 minutes. Glycogen stores adequate with normal eating. Focus on topping up and feeling light.
- Olympic (1.5km/40km/10km): 2-3 hours. Significant glycogen use. Proper pre-race meal essential.
- Half/70.3 (1.9km/90km/21.1km): 4-7 hours. Major glycogen depletion. Carb loading and race nutrition crucial.
Longer races require more aggressive carb loading in the days before. Sprint triathlons can be fuelled with normal eating plus a good pre-race meal.
Race Day Timing Strategy
Aim for 1-4g carbohydrate per kg bodyweight 1-4 hours before endurance events. For most triathletes, 1-2g/kg works well 3-4 hours out.
Optional 20-40g easily digestible carbs. Some athletes prefer to skip this to ensure stomach is empty for the swim.
Small amount of simple carbs if desired - half banana, dates, or natural energy gel. Many athletes do this just before entering the water.
For Olympic distance and above, consuming 30-60g carbs per hour during the bike (and possibly run) maintains performance.
The Night Before
For Olympic distance and longer, carbohydrate loading in the 24-48 hours before increases muscle glycogen stores. This can improve performance in events lasting over 90 minutes.
Night Before Dinner Options
Pasta with Tomato Sauce
Classic carb loading meal. White pasta digests easily. Keep sauce simple - no heavy cream or excessive meat.
Rice with Chicken
White rice is excellent for glycogen storage. Lean protein without excess fat or fibre.
Jacket Potato
Potatoes are highly effective for glycogen loading. Simple toppings - skip the heavy cheese.
Risotto
Carb-dense, easy to digest, palatable. Chicken or seafood risotto works well.
Race Morning
Most triathlons start early (7-8am), meaning you need to eat 3-4 hours before - that's a 4am alarm for breakfast. Set everything out the night before to minimise early morning stress.
Race Morning Breakfast Options
Porridge with Banana
The classic triathlete breakfast. Oats provide sustained energy, banana adds quick carbs and potassium.
Toast with Peanut Butter & Banana
Carbs from toast, some protein and fat from peanut butter. Easy to eat at 4am.
Bagel with Jam
Dense carbs, very digestible. White bagels are easier on the stomach than wholemeal.
Rice Cakes with Honey
Very light on the stomach. Good option if you struggle to eat early or before swimming.
The Swim Consideration
Swimming with food in your stomach is uncomfortable at best, nauseating at worst. The horizontal position and abdominal compression make digestion difficult. This is why timing matters so much in triathlon.
Guidelines for swim-friendly nutrition:
- Finish your main meal at least 3 hours before swim start
- Keep any top-up snacks small and easy to digest
- Avoid high-fat, high-fibre foods that sit heavily
- Test your race morning routine in training swims
Final Pre-Swim Options (30 mins before)
Natural Energy Gel or Dates
Designed for rapid absorption. Take 15-20 minutes before entering the water with a few sips of water.
Half Banana
Quick carbs, minimal volume. Easy on the stomach.
Fast sugar, tiny volume. Many triathletes swear by this.
Sports Drink Sips
Combines final hydration with small carb boost. Don't gulp.
What to Avoid Before Triathlon
- Large meals too close: Nothing substantial within 3 hours of swim start
- High-fibre foods: Can cause GI distress across all three disciplines
- High-fat foods: Slow digestion means discomfort on the swim and early bike
- New foods: Race day is NOT for experiments. Stick with what you've tested
- Excessive caffeine: Some helps, too much causes GI issues and jitters
- Over-hydration: Drinking too much before the swim can cause discomfort and hyponatremia risk
Distance-Specific Guidance
Sprint Triathlon
Under 75 minutes of racing - your glycogen stores are adequate with normal eating. Focus on a light, carb-based breakfast 2-3 hours before. You probably don't need race nutrition during - just finish what you've stored.
Olympic Triathlon
2-3 hours of racing. A proper carb-rich dinner the night before, substantial breakfast 3-4 hours before, and you may benefit from dates or natural energy gels during the bike leg. This is where nutrition starts to become a factor.
Half Ironman / 70.3
4-7 hours of racing. Carb loading for 2-3 days before is beneficial. Larger pre-race breakfast. Race nutrition becomes critical - you'll need to consume 40-60g carbs per hour on the bike and potentially during the run. Test everything in training.
Hydration
Start hydrating the day before - don't try to catch up on race morning. Aim for 5-7ml per kg bodyweight in the hours before exercise. For a 70kg athlete, that's 350-490ml.
Don't over-drink on race morning. Your wetsuit feels tighter with a full bladder, and excessive fluid can cause hyponatremia in longer races. Sip steadily, but trust your pre-race hydration from the day before.
Your Pre-Triathlon Nutrition Summary
Night before: Carb-rich dinner (pasta, rice, potatoes) - especially important for Olympic+ distances. Race morning: Breakfast 3-4 hours before swim start. 1-2g carbs/kg from easily digestible sources. Final fuel: Optional small carbs 20-30 minutes before swim - dates, natural energy gel, half banana, few sweets. Hydration: Start day before, 5-7ml/kg in final hours, don't over-drink. Key rule: Nothing heavy within 3 hours of swimming.
After your race, recovery nutrition helps you bounce back. Read our guide on what to eat after a triathlon for recovery recommendations.
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