Here’s the truth: athletes obsess over gels and bottles on the bike and run while ignoring the most significant contributor to performance and body composition—your everyday nutrition.

Let’s walk through a comprehensive 70.3 fueling strategy, from day-to-day habits to the race morning meal. We won’t even forget the post-race beer or champagne! This guide combines science-backed advice with real-world tips and Fuelin’s personalised planning system to help you reach the start line full of confidence and finish your race with a smile. A 70.3 Ironman is a serious challenge: 1.9km swim, 90km bike, and a 21.1km run. Let’s make all the effort in training pay off on your big day.

KEY TAKEAWAYS:

1. Your daily nutrition is just as crucial as your race-day plan. Nail the basics with high protein, periodised carbs, and strategically fueled training sessions to support body composition health and performance.

2. You can’t wing a 70.3. Race fueling success depends on months of targeted practice and testing. It is not only what you do on race day. Do you want to leave your fueling and hydration to chance after all those weeks of training?

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1. Eat to Train, Not Just to Race

Daily nutrition is the backbone of 70.3 performance

Far too many athletes become fixated on what to eat during training sessions. But unless your everyday diet supports your training volume and body composition goals, you’re going to hit the wall—figuratively and literally.

Here’s the Fuelin approach to daily nutrition and fueling:

High Protein Intake (2.0–3.0g/kg/day)

This supports muscle repair, immune health, and lean mass retention, particularly during periods of energy deficit. For example, a 70kg athlete should aim for 140–210g of protein daily.
‍Despite reports about the safety considerations of protein, higher protein intakes are necessary for you as an endurance athlete to thrive. Endurance athletes have higher protein needs than strength athletes.

Periodised Carbohydrates (1.8g - 12g/kg/day)

Match carb intake to your training load—low on recovery days (1-1.8g/kg), moderate on aerobic sessions (1.9-4g/kg), and high (4.1–12g/kg) on big training days or brick sessions. This approach helps with metabolic flexibility, ensures glycogen restoration, and optimises fat adaptation. Consuming carbs during your training will not interfere with the ability to utilise fat as a fuel source, as evidenced by these cyclists and Holly Lawrence. 

Fats for Energy (0.8–1.5g/kg)

‍Essential for hormone health and energy, especially on lower-carb days. Fat intake may increase during the base phase or off-season, but must taper back as intensity and race-specific training increase.

Daily Hydration & Micronutrients

Underappreciated but vital. Sodium, magnesium, iron, and calcium losses add up across sessions. These should be addressed through targeted electrolyte drinks and whole-food choices, along with baseline blood work if necessary.  Regarding blood testing, we recommend testing twice a year. Depending on your individual needs and current health status, these issues may be best addressed by consulting a healthcare professional of your choice. Seeking out a nutritionist or dietician with appropriate tertiary education and accreditation combined with an expertise in endurance sports should be your priority. 

👨 MALE TAKEAWAY:‍

You’re likely under-consuming protein—start with 2.2g/kg as a baseline and don’t fear fats. Keep carbs strategic based on the work you’re doing. Carbs are your friend for recovery after training sessions.

👩 FEMALE TAKEAWAY:‍

Periods of low energy availability can disrupt hormones and performance. Don’t cut carbs too drastically—prioritise post-training fueling and sufficient daily protein to stay strong and regular. You, too, are likely under-consuming protein; aim for the same range as your male colleagues. This is regardless of your age, even if you are peri- or menopausal. - 2.0-3.0g/kg is right for everyone doing a 70.3.

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2. Practice Makes Permanent: Training the Gut & Sweat Testing

Start 12 weeks out—test, tweak, repeat!

No matter how “clean” your diet is, you need to condition your gut to absorb the race-day fuel. Your goal is to match the carb intake (g/hr) and fluid needs you’ll use in competition. Don’t let your “clean” diet cause underfueling and prolonged periods of low energy availability.

Sweat and Carb Capacity Testing (via Fuelin)

We help you measure your:

- Sweat rate (L/hour) and sodium loss (mg/L) - understand your sweat loss, your fluid intake and your recommended fluid intake on the bike and run.

- Carbohydrate Capacity (g/hr) during bike and run. Learn what your current intake of grams/hour is, what your target should be and how you feel as you ramp up your intake.

This data is integrated into your Fuelin plan, so every long session becomes a mini dress rehearsal for race day.
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The 3 Crucial Practice Sessions (12–6 Weeks Out)

1. Bike Long Ride (Fueling Focused) – mimic race conditions

2. Brick Session (Bike + Run) – test transition fueling strategies. Discuss with your coach the possibility of incorporating a longer run off the bike to practice fueling during the run.

3. Hot Environment Session – Simulate Sweat Stress on the bike and run. Get comfortable being uncomfortable to ensure you know your requirements in hot race conditions. 

Each includes prescribed carbs (g/hr), fluid targets (ml/hr), sodium amounts, and notes for GI feedback.
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👨 MALE TAKEAWAY:‍

Don’t wait until race week to try 90–120g/hr of carbs. Your gut needs weeks to adapt to this load. Remember, not everyone needs extremely high carbs in training for racing. Your power output determines this.

👩 FEMALE TAKEAWAY:‍

Start with 40-70g/hr and build up. Women tend to report more GI issues, so consistent practice is key to prevent race-day distress. Your absolute power numbers on the bike and the run will help determine your carb target per hour.

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3. Carb Loading: It’s a Strategy, Not a Buffet

Start two (2) days before, not the night before

Carbohydrate loading increases muscle glycogen stores, boosts endurance, and can improve performance by 2–3%—a significant edge in a 4–7 hour race. 

Day-by-Day Breakdown:

‍✅ Do’s:

Choose low-fibre, low-fat, moderate-protein options

Use carb drinks (like maltodextrin mixes) to reduce volume of food

Practice befire big training weekends.

❌ Don’ts:

Don’t try a new food or supplement

Don’t over consume fat or protein.

Don’t skip hydration—fluids help transport carbs (they can also be part of the carb load). Most athletes stuff up the carb load!
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👨 MALE TAKEAWAY:‍

You will need more than you think—aim for a minimum of 8g/kg of carbs. It’s not just pasta; liquid carbs make it doable. The amount of carbs should be based on grams/kilogram, not a percentage of your total caloric needs for the day.

👩 FEMALE TAKEAWAY:‍

Start early and front-load the day with higher intake of carbs for breakfast and morning snacks.  Avoid bloating by eating low-fibre, easy-to-digest carbs like rice cakes, bananas, and glucose drinks. This is not a time for your green vegetables.

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4. Race Day Morning: Calm, Carbs, Caffeine

Your fueling starts 3 hours before the cannon goes off

You want to start the race with full glycogen stores, optimal blood glucose, and caffeine stimulation. Avoid rushed meals or high-fibre options that can backfire mid-swim.

Pre-Race Breakfast (3–4 hours out)

- 20–40g protein with 10–30g fat and 100–250g carbs (1.5–3.0g/kg BW) An example of what this could look like. 

- Whey or plant protein milk over white rice, topped with yoghurt, maple syrup, and banana, served with slices of white toast topped with almond butter, served with a coffee of your choice.

60 Minutes Out

- 50–100g carbs (bloks, gels, rice balls, drink)

-100–200mg caffeine (if tested and tolerated), Pills, gels or drink format)

-Sip on an electrolyte drink with 500 to 2000mg sodium (~500–1000ml depending on individual needs)

10–5 Minutes Pre-Swim

- 1–2 gels (25–60g carbs) - depending on gels used.

👨 MALE TAKEAWAY:
Get your carbs in early and don’t forget your caffeine (if you use it) — it reduces perceived effort and can help delay fatigue.

👩 FEMALE TAKEAWAY:

Don’t skip breakfast due to nerves. You have practised your race day breakfast many times, so the day of the race is nothing new or unfamiliar.

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5. On-Course Fueling: Bike & Run Strategy

Hit your numbers or pay the price later.

During the race, your fueling plan is a continuation of everything you’ve practised in training —nothing new. Fuelin sets targets based on your individual testing and integrates this into your training sessions.

BIKE

Males: Target: 90–120g/hr carbs

Females: Target: 70–120g/hr carbs

You will need to adjust this intake based on  your absolute power output. Lower watts = lower burn = lower carb numbers. The race temperature wil also play a crticial role in carbohydrate intake on the day (hotter = more sweat = less fluid tolerance and cooler = less sweat = reduced fluids as carbs).  The key will be alternating between gels, drinks, and chews based on your training progress. Your sodium needs will vary base don how salty a sweater your are and how long you will be riding for. Amounts vary from 300–2000mg/L based on your testing and sweat rate.

RUN

Males: Target: 70–100g/hr

Females: Target: 50–90g/hr

Expect higher sweat rates on the run. Come off the bike well-hydrated to reduce the risk of dehydration on the run. Getting this amount right also minimises the risk of gut slosh. Understanding your sweat loss, fluid intake, and recommended fluid intake during biking and running via continuous testing during your training blocks will allow this to happen. It won't be a guessing game, and you'll have a level of confidence in your plan that few athletes rarely possess. Remember to stick with easy-to-digest options (gels, chews, sports drinks that you have practised with in training. Remember - NOTHING NEW ON RACE DAY. 

👨 MALE TAKEAWAY:‍

Fuel to match your power. Don’t overfuel if you’re riding lower watts, especially on a hilly course or hot day. Follow your plan based on your training results. 

👩 FEMALE TAKEAWAY:

Start fueling within 10 minutes on the run. Smaller doses, administered more frequently, can help avoid GI distress and energy drops. Use the gels you have trained with. This might mean you have to carry your fuel in a belt or pockets.

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6. Post-Race Recovery: Refuel & Rejoice

Recovery starts the moment you cross the finish line

Immediate (within 2 hours)

If you have access to a scale and can weigh yourself, please do. Aim to rehydrate with 150–200% of the weight lost. You can use a combination of water, milk, carb/electrolyte drinks. If you fancy a cold beer or champagne - that counts too 🍻Just don’t over do it.

Nutrition (within 60 minutes)

40–60g protein + 100g carbs. I will always recommend athletes have a dry shake in their gear bag.. This means a protein shaker with 40–60g whey or plant protein + 20g creatine. When the race finishes, simply add a pint of milk (choc, full-fat or nut milk) and shake and skull. Try to eat at least two bananas with the protein shake for an easy 50g of carbs. After this, try to get more calories in within the next 60 minutes. A pizza, steak or a good piece of fish with vegetables and rice will have you bouncing around the next day.

Bonus Recovery Moves

Dip in the ocean/pool or an easy 10-min spin or walk will do wonders for helping clear metabolites and inflammatory markers from your system. Do this with your recovery drink in hand.

👨 MALE TAKEAWAY:‍

Don’t delay the protein. Get that shake in, and keep fluids flowing—especially if you lost more than 2% body weight.

👩 FEMALE TAKEAWAY:‍

Recovery is about replenishing calories, restoring glycogen, aiding muscle repair, and supporting immune function. Eat ASAP, and don’t shy away from protein or carbs.

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Final Thoughts

Fueling a 70.3 is both science and practice. The best results come from athletes who integrate fueling into their everyday life, not just race day. At Fuelin, we’ve helped thousands of athletes hit personal bests and finish line smiles by creating repeatable systems, not guesswork.

Use this guide as your starting line. Want to go further? Download the Fuelin app, connect your training platform (TrainingPeaks, HumanGo, TriDot, or Final Surge), or use Fuelin to build your training calendar. Then start tracking your daily nutrition, log your first sweat and carb tests, and we’ll build your plan around you. See you at the start line!

Thanks for reading,

Scott

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