70.3 Nutrition Plan: How to Fuel a Half Ironman Without Guessing
A half Ironman is not just a long workout with more gels. Learn how to plan carbs, sodium, fluids, breakfast, bike fueling, run fueling, and recovery for 70.3 training and race day.
Quick Answer
A strong 70.3 nutrition plan starts with a familiar carb-focused breakfast, then targets roughly 60-90g carbs per hour on the bike, 30-60g carbs per hour on the run, 400-800ml fluid per hour, and 500-900mg sodium per hour adjusted to sweat rate and heat. MAVR turns your race plan and training sessions into a personalized fueling timeline.
A 70.3 race is long enough that nutrition becomes a performance limiter, but fast enough that your stomach can ruin the day if you overdo it.
That is why copying a full Ironman plan usually backfires. You need enough carbohydrate to protect your run, enough sodium and fluid to stay steady, and a plan simple enough to execute when your heart rate is high.
The 70.3 Fueling Targets
| Race segment | Carb target | Fluid target | Sodium target |
|---|---|---|---|
| Pre-race breakfast | 1-3g/kg, 2-4 hours before start | 500-750ml before transition closes | 300-600mg if you sweat heavily |
| Bike | 60-90g/hour | 400-800ml/hour | 500-900mg/hour |
| Run | 30-60g/hour | Drink to thirst plus aid stations | 300-700mg/hour |
| Post-race | 1-1.2g/kg in first 2 hours | 150% of fluid lost | Include sodium with recovery meal |
These are starting ranges, not commandments. A 58kg athlete racing in cool weather and a 90kg heavy sweater racing in humidity should not use the same plan.
Breakfast: Start Full, Not Stuffed
Your pre-race breakfast should top up glycogen without leaving food sitting in your stomach during the swim. Keep it familiar, carb-focused, and low in fat and fiber.
- 3-4 hours before: bagel with honey, banana, sports drink, or oatmeal if you tolerate it well.
- 60-90 minutes before: small carb top-up if breakfast was early.
- 10-15 minutes before swim start: optional gel or sports drink only if practiced.
- Avoid heavy nut butters, large dairy portions, fried foods, and high-fiber cereals.
The Bike Is Where You Save Your Run
Most athletes underfuel the bike because they feel fine early. Then they reach the run with low glycogen, rising core temperature, and a stomach that no longer wants concentrated gels.
The bike is your best fueling window. You are seated, impact is lower, and you can carry bottles, gels, chews, or solids. Use that advantage.
| Bike split | Carbs to carry | Simple setup |
|---|---|---|
| 2:30 bike | 150-225g total | Two carb bottles plus 2-3 gels |
| 3:00 bike | 180-270g total | Two carb bottles, gels, and aid-station backup |
| 3:30 bike | 210-315g total | Concentrated bottle plus water, gels, and sodium plan |
The Run: Smaller Doses, Earlier Than You Think
The half-marathon run is where athletes discover whether their bike fueling worked. If you arrive depleted, the run becomes survival. If you arrive overfed, the run becomes a GI problem.
- Start fueling in the first 10-15 minutes of the run, before you feel low.
- Use smaller doses more often: gel bites, chews, sports drink, or cola later if needed.
- Aim for 30-60g carbs per hour depending on gut tolerance and run duration.
- Use aid stations for fluid, but do not rely on them for your entire carb plan unless you know the on-course products.
Practice the Plan in Training
Your long rides and brick workouts are not just fitness sessions. They are nutrition rehearsals.
- Practice breakfast before long rides that start at race time.
- Use race-like carb targets on rides over 2.5 hours.
- Practice taking fuel in aero position, not just sitting up at stoplights.
- Run 20-40 minutes off the bike after fueling hard enough to test your stomach.
- Record what worked, what caused bloating, and what your energy felt like in the next session.
How MAVR Builds a 70.3 Plan
MAVR is built for athletes who already have training data. Instead of giving a generic carb chart, it reads the context around your sessions and turns that into fueling actions.
- Estimates race duration from your expected swim, bike, and run splits.
- Calculates carb, sodium, and fluid targets by segment.
- Adjusts daily macros around long rides, bricks, recovery days, and taper week.
- Turns practice sessions into repeatable race-day timing.
MAVR turns your race goal and training schedule into a personalized 70.3 nutrition plan.
Build My 70.3 Fueling PlanFrequently Asked Questions
How many carbs per hour do I need for a 70.3?
Most athletes should start with 60-90g carbs per hour on the bike and 30-60g per hour on the run. The bike target is higher because digestion is easier with less impact. Practice these targets in training before race day.
Should I eat solid food during a half Ironman?
Some athletes tolerate small solid foods early on the bike, but gels, chews, drink mix, and simple low-fiber options are usually safer. Avoid solid food late on the bike and during the run unless you have practiced it repeatedly.
Do I need salt tablets for a 70.3?
Maybe. Heavy sweaters and hot races often require more sodium than standard sports drink provides. Start with 500-900mg sodium per hour on the bike and adjust based on sweat rate, conditions, and GI tolerance.
Can MAVR plan nutrition for triathlon training?
Yes. MAVR supports endurance athletes who train across swim, bike, run, strength, and recovery days, then adjusts nutrition targets around the actual workload instead of giving one flat calorie target.