Training For an Ironman: Nutrition

An athlete can be more than physically and mentally prepared for an Ironman but if they don’t have a nutrition plan, their day will end abruptly.

A recreational athlete can expend from 7000-12000 calories during an Ironman event depending on their size, finish time, and intensity throughout the race. This poses a significant challenge for refueling since the body only stores about 1800-2200 calories as glycogen but over 80,000 calories as fat. The aerobic energy system predominates during exercise intensities of 60-80% of maximum heart rate, thus the body will utilize about 50% of its energy from glycogen and the other half from fat. Protein is also utilized but at lower absolute amounts than glycogen and fat. At exercise intensities of 80% or greater of maximum heart rate, fat cannot be utilized as effectively as a fuel and will only provide approximately 25% of the total energy that the body needs with the remaining from glycogen (and again, a very small amount from protein).

A recreational athlete will usually stay within the intensity range of 60-80% of their maximum heart rate but more competitive athletes can sustain an intensity greater than 80% for an Ironman. Having said this, we will figure this Ironman nutrition plan based on relatively equal amounts of energy being provided from glycogen and fat.

Eating for an Ironman is not difficult but does require planning. The following example will be based on a recreational Ironman athlete who is a male, weighs 155 pounds and is 5 feet, 10 inches tall.

Estimated calorie expenditure during the Ironman:

Swim:
Predicted finish time: 1 hour, 30 minutes
Speed: moderate
Calories expended: approximately 650

Bike:
Predicted finish time: 6 hours, 30 minutes
Speed: 17-19 miles per hour
Calories expended: approximately 5000

Run:
Predicted finish time: 5 hours
Speed: 6.7 mph, 9 minutes/mile
Calories expended: approximately 3500
Approximate finish time: 13 hours
Approximate total calories expended: 9150 (not including transitions)

Considering this athlete has a glycogen storage capacity around 1800 calories, he will exhaust his internal stores in the first hour of the bike so it is crucial for him to constantly replace what is lost during the race. If this athlete needs 9150 calories during his Ironman and will use up his 1800 stored calories as glycogen at the end of the first hour of the bike, this will leave 10 hours where he will have to take in the required calories to avoid a negative energy balance that may affect his performance. With a remaining 7500 calories needed to consume the last 10 hours of the Ironman, this equates into this athlete consuming 750 calories per hour. However, this is impossible because the body cannot absorb this many.

The body can absorb about 1 gram of carbohydrate per minute of moderately intense exercise-60 grams per hour, or 240 calories. While this does range depending on the athlete’s size, gender and genetics, there is a ceiling of around 350-400 calories that the body can absorb each hour.

The point is that the athlete will not be able to eat or drink enough calories throughout the Ironman race to adequately replace what is lost. So, the nutrition plan should be one that emphasizes the following:

1.  Proper pre-race nutrition and carbohydrate loading to ensure that the muscle and liver glycogen stores are at their fullest.

2. Adequate fluid intake to prevent or delay dehydration.

3. Maximal calorie intake per hour that can be supported by the athlete’s body to deliver the necessary energy needed for muscular contraction.

4. Proper nutrition after the race to enhance recovery.

The athlete has spent endless hours training for the physical part of their Ironman should begin their nutrition race plan two weeks prior to race day. Here is a list of guidelines to follow.

Nutritional goals:

1. Be aware of what you are eating and don’t do anything too different.

2. Eat at least 4 grams of carbohydrate (16 calories) per kilogram of body weight.

3. Eat 1.2-1.4 grams of protein (5-6 calories) per kilogram of body weight.

4. Eat approximately 0.8-1.0 grams of fat (7-9 calories) per kilogram of body weight.

5. Slowly increase the amount of sodium used in daily cooking (a couple of shakes of the salt shaker here and there will suffice).

6. Remain hydrated indicated through clear or pale yellow urine.

Nutrition goals:

1. Eat at least 5 grams of carbohydrate (20 calories) per kilogram of body weight.

2. Slowly decrease the amount of fiber eaten in the normal diet.

3. Remain hydrated indicated through clear or pale yellow urine.

4. Decrease the amount of hot spices used.

5. ontinue to use the salt shaker when cooking or eating.

Nutrition goals:

1. Eat up to 10 grams of carbohydrate (40 calories) per kilogram of body weight.

2. Be more generous with salt and add it every chance you have to your meals and/or eat more salty snacks.

3. Drink more sports drink than water throughout the day.

4. Eat a low fiber diet.

5. Don’t eat anything new.

6. Remain hydrated indicated through clear or pale yellow urine.

1. Eat up to 10 grams of carbohydrate (40 calories) per kilogram of body weight.

2. Eat your last large carbohydrate dinner two nights before the race.

3. Drink more sports drink than water throughout the day.

4. Eat a low fiber diet.

5. Don’t eat anything new.

6. Remain hydrated indicated through clear or pale yellow urine.

1. Eat up to 10 grams of carbohydrate (40 calories) per kilogram of body weight.

2. “Graze” throughout the day, never allowing your blood sugar level to drop. Carry high carbohydrate and salty snacks with you everywhere.

3. Taper your eating throughout the day. That is, eat a normal size breakfast, a lighter lunch and an even lighter dinner.

4. Sip on sports drink throughout the day.

5. Drink at least 16 ounces of sports drink and a high carbohydrate snack (energy bars work well) before going to bed.

6. Eat low fiber foods.

7. Don’t eat anything new.

8. Remain hydrated indicated through clear or pale yellow urine.

Race day nutrition is highly individualized and often times the general rule of thumb is, “If it tastes OK in training, chances are it won’t work in a race. If it tastes great in training, it might work in a race.” Because racing situations greatly magnify and change the taste of all food and drink, it is important to remember that the best source of calories for an Ironman is the one that you can get down and keep down. Fluids or gels are usually a better choice than solid foods. That said, here are general recommendations:

You will need to eat something to refill your glycogen stores because you are coming off of an overnight fast. Eat about 2-4 grams of carbohydrate per kilogram of body weight 2-3 hours before the start of the race and drink 17-20 ounces of sports drink during this time also. Drink 7-10 ounces of a sports drink about 10-20 minutes prior to the start. Remember, do not try anything new on race morning.

As previously stated, each athlete will absorb different amounts of calories per hour so it is important to experiment with quantity during training. In general, you should consume 60-100 grams of carbohydrate (240-400 calories) per hour of exercise. Because fluid empties from your stomach very differently from other athletes, you should also experiment with fluid quantities during training. In general, you should consume 24-40 ounces of fluid per hour. It is important to try to drink more sports drinks rather than water during the race in order to replenish needed electrolytes, most notably, sodium.

Because you will be in the water for over 1 hour, it is important to begin your nutrition plan immediately when getting on your bike. Remember, the most important piece of your nutrition plan is hydration.

Hydration is just as important after the race as it is during the race. Drink 24 ounces of sports drink for every pound that you lost during the race. Do this immediately after finishing because chances are, you won’t feel like eating solid food. That is okay as long as you drink a sports drink that contains sodium and carbohydrates.

Eat 1-1.5 grams (4-6 calories) of carbohydrate within the first 30 minutes of finishing. There is still debate in the scientific world regarding the addition of protein to recovery nutrition but preliminary studies do show that the addition of protein to post-race nutrition could enhance muscle repair and provide important nutrients for the immune system. A general rule of thumb is to consume a 3:1 ratio of carbohydrates to protein after a race.

Don’t forget sodium. Sodium facilitates the entry of glucose and water into cells so choose sports drinks with sodium in them and high sodium snacks.

You can then have a “normal” mixed meal of carbohydrates, protein and fat 2 hours after the finish.

Some helpful tips for Ironman nutrition:

1. Have a back-up plan just in case you cannot replicate what you have done in training during your Ironman.

2. Think about using salty foods or salt supplements during the race if you are a heavy sweater and if the environmental conditions will be hot and humid.

3. Hydrate, hydrate, hydrate. If everything else fails, you must still drink.

Don’t underestimate your nutrition plan during your Ironman. You have spent a good portion of a year physically and mentally preparing for this. Don’t let poor nutrition planning prevent you from crossing the finish line.

Feel free to contact me at [email protected] if you have any questions.