Fueling Long Course Triathlons: Nutrition Tips for Half and Full Ironmans

14 January 2026

Triathlon isn't just about swimming, biking, and running—it's a battle of endurance, strategy, and, most importantly, fueling. If you're tackling a Half (70.3) or Full (140.6) Ironman, getting your nutrition right is just as vital as your training.

Think about it: Your body is the engine, and food is the fuel. Would you expect a car to run 140+ miles without refueling? Nope. The same goes for your body during a grueling endurance race.

In this guide, we’ll dive deep into the best nutrition strategies for long-course triathlons to ensure you don’t hit the dreaded bonk.

Understanding Triathlon Nutrition Basics

Triathlon fueling is a mix of science and personal practice. What works for one athlete might be a disaster for another. But at the core of any endurance race nutrition plan, there are three essentials:

- Carbohydrates – The primary energy source for endurance athletes. Your body can only store so much glycogen, so replenishing carbs during the race is crucial.
- Protein – Supports muscle repair and reduces breakdown. While not a primary fuel source during the race, having enough protein in your diet helps with recovery.
- Fats – A secondary fuel source, especially useful during lower-intensity portions of a long race.

Now that we’ve got the basics down, let's talk about fueling strategies for both Half and Full Ironmans.

Pre-Race Nutrition: Setting the Foundation

Your race-day performance starts long before you hear the starting gun. The right pre-race nutrition strategy ensures your energy reserves are topped up and ready to go.

The Week Leading Up to the Race

In the week leading up to your race, focus on:

- Carb Loading (Smartly!) – Increase carbohydrate intake 2–3 days before the race to maximize glycogen stores. Don’t just binge on pasta—opt for whole grains, fruits, and starchy vegetables.
- Hydration – Proper hydration begins well before race day. Increase fluid intake and include electrolyte-rich drinks to keep sodium and potassium levels in check.
- Avoiding Heavy, High-Fiber Foods – While fiber is great for your everyday diet, too much can lead to digestive issues on race day. Be mindful of excessive fiber intake 24–48 hours before the event.

Race Morning Nutrition

Breakfast should be eaten 2–3 hours before the race start. Stick to something familiar and easy to digest, like:

- A bagel with peanut butter and banana
- Oatmeal with honey and a protein shake
- A smoothie with carbs, protein, and some healthy fats

Aim for 300–600 calories, focusing mostly on carbohydrates with a little protein and fat to prevent energy crashes.

During the Race: Fueling Strategies for Success

Now, let’s break down race-day nutrition based on each discipline.

Swim: Prepping for the Bike

You obviously can’t eat during the swim, but you should top up your glycogen just before hitting the water. Many triathletes sip on a sports drink or take a gel 15 minutes before race start to ensure their energy levels are primed.

Bike: The Nutrition Powerhouse

The bike leg is where you can consume the most calories. Since cycling is lower impact (compared to running), your digestive system can handle more food.

Key Bike Nutrition Tips:

- Aim for 200–400 calories per hour, depending on your race duration and body size.
- Carbohydrate intake: 60–90g of carbs per hour (mixing glucose and fructose sources for better absorption).
- Hydration: Drink 500–750ml of fluids per hour, adjusting based on sweat rate and temperature.
- Electrolytes: Take in 500–1000mg of sodium per hour to replace lost sweat and prevent cramping.

What to Eat on the Bike

- Energy gels, chews, or bars
- Sports drinks (high in carbs and electrolytes)
- A mix of real food like bananas, PB&J sandwiches, or rice cakes (especially for full Ironmans)

Many long-course triathletes set a nutrition alarm on their bike computers to remind them to eat every 15–20 minutes, preventing energy dips.

Run: Survival Mode and Sustaining Energy

Once you’re off the bike, things get trickier. The body has a harder time digesting solid food while running, so liquid and gel-based nutrition becomes more critical.

Key Run Nutrition Tips:

- Aim for 150–300 calories per hour (depending on tolerance).
- Stick to fast-digesting carbs like energy gels, chews, and sports drinks.
- Hydration: Sip water and electrolyte drinks at every aid station.
- Listen to your stomach: If you’re feeling bloated, back off solids and switch to liquids.

Common Race-Day Nutrition Mistakes

1. Ignoring Nutrition in Training – Never try new foods on race day.
2. Not Taking in Enough Calories – Over time, an energy deficit catches up to you.
3. Overhydrating Without Electrolytes – Too much water without sodium can lead to hyponatremia (dangerously low sodium levels).
4. Waiting Too Long to Start Nutrition – Start fueling early and stay consistent.
5. Ignoring Caffeine Strategy – Caffeine can boost performance, but overuse or trying it for the first time on race day can backfire.

Post-Race Recovery: Refueling for Repair

You crossed the finish line—congrats! But your nutrition plan isn’t over yet. Proper post-race fueling helps you recover faster and feel human again.

Key Recovery Nutrition Tips

- Post-race meal (within 30–60 minutes): Aim for a 3:1 ratio of carbs to protein (e.g., chocolate milk, a smoothie, or a real meal with lean protein and carbs).
- Rehydrate with electrolytes to replace lost fluids and minerals.
- Keep eating balanced meals over the next 24–48 hours to support muscle repair.

Dial in Your Nutrition for Triathlon Success

At the end of the day, nutrition is deeply personal. What works for one triathlete might send another straight to the porta-potty. The key? Practice your race-day nutrition during training.

Test different foods, timing strategies, and hydration plans on long training rides and brick workouts to fine-tune what works best for you.

Mastering triathlon fueling is just as important as swim, bike, and run training. Nail your nutrition, and you’ll power through the miles feeling strong, avoiding the dreaded bonk, and crossing the finish line with a smile.