Nutrition for a Half Ironman

For races like the Ironman 70.3 or other 4- to 7-hour events, nutrition is absolutely key. In shorter triathlons, you can get away with some nutritional mistakes without much consequence. In a half Ironman, however, nutritional mistakes are likely to cost you dearly. When you ask athletes why they didn’t do well in a race, they often cite nutrition as the main reason.

In this article, we'll look at the basics of nutrition for this type of race, list some general rules and common mistakes. For clarity, some things are simplified — a more advanced plan that also takes into account individual differences between athletes will be the subject of another article.

Three main nutritional problems:

1. Energy depletion – “walls”, “bangs” or simply losing the ability to keep up the pace in the final part of the race.

2. Dehydration – which can gradually worsen during the race and limit performance.

3. Digestive problems – such as stomach cramps, bloating, and other problems that negatively affect performance.

Fueling

The main source of energy is carbohydrates – especially if you plan to complete the race closer to 4 hours than 7 hours. The body has approximately 500 g of carbohydrate reserves (about 2000 kcal), which is not enough for the entire race. Theoretically, this could be enough for 3 hours of performance, but it is necessary to replenish the reserves right from the start – carbohydrate absorption takes time, and when the reserves are depleted, it is difficult to return.

General recommendation :
Goal = approximately 60 g of carbohydrates per hour (1,2).
This can be a gel, bar, sports drink, or a combination. If you use a solid food, it should be low in fat, protein, and fiber. Faster athletes usually choose a liquid form because chewing at high intensity is difficult.

Examples for 60 g/h:

• 2 gels + some sports drink

• 1 gel + 1 bottle of sports drink

• 1 bar + half a bottle of sports drink

Check the exact ingredients on the labels of the products you plan to use.

Hydration

"Drink according to thirst" is a recommendation more suitable for slower competitors. Faster competitors should have a plan. The first part of the race is suitable for replenishing both fluids and carbohydrates, because the digestive tract is still functioning well. In the second part of the race, absorption may be limited.
Don't drink excessively - the goal is to lose about 1-2 kg (2-4 pounds), weight gain would indicate excessive fluid intake.
Remember that proper hydration starts days before the race .

Digestive problems

30-70% of athletes experience gastrointestinal problems during a half Ironman. For some, they are mild, for others they can significantly affect performance. The causes may not be related to food — sometimes they only appear on race day (it can be the effect of stress).
The main risk factors include:

• high fiber intake

• high fat intake

• overly concentrated carbohydrate drinks (3)

Plan ahead

Think about it:

• carbohydrate sources (gels, drinks, bars)

• how much fluid you will need and where you will refill it (supply, refreshment stations)

• maintain 60 g of carbohydrates per hour and stay hydrated to avoid significant weight loss

Your body is the best laboratory – weigh yourself before and after training and observe the changes.

The most common mistakes in the race

1. Sticking to the plan blindly – ​​if something goes wrong (e.g. you lose the bottle or have digestive problems), be flexible and adjust the plan. Forced intake can make the situation worse.

2. Testing new products for a race – never use a product that you haven't tested in training.

3. More ≠ better – once you meet your basic nutritional needs, adding more calories or fluids will not improve performance and may actually be detrimental.

Tips:

• Sodium losses do not have a major impact on performance for most athletes, so sodium supplementation is not a priority. Excessive intake can cause digestive problems.

• Caffeine (about 3 mg/kg an hour before the start – equivalent to a large coffee or two espressos) may help some athletes. Experiment with what works for you in your training.

These are the very basics of proper nutrition for a half Ironman. Many athletes ignore them and focus more on the details or supplements. The next step is to customize the plan — but that requires measurements and an individual approach.