During long distance endurance events such as an Ironman, Half Ironman, ultra marathon, or marathon our bodies will burn far more calories than we are capable of consuming. Take in too few calories and you’re going to hit the wall and bonk. Take in too many calories and you could be sidelined with gastrointestinal distress(stomach and intestine issues). You need to find a balance and rely on this plan come race day.
What can we absorb during endurance activities? Research tells us that our bodies can process 30 – 60 grams of carbohydrates per hour at a moderate intensity (very wide range because everyone is different). This amounts to a calorie range of 120 – 240 calories per hour (4 calories per gram of carbohydrate).
If you are using liquid calories, research shows that a 6-8% carbohydrate combination is ideal for stomach emptying (reducing the chance of gastrointestinal distress) The carbohydrate percentage is based on grams of carbohydrates:100ml of liquid. So let’s say you are drinking one water bottle per hour and let’s also assume that this fluid contains 18 ounces and 140 calories of carbohydrates. This amounts to 532 ml of fluid and 35 grams of carbohydrates (4 calories per gram). So, our drink combination would be 35 grams/532 ml = 6.5% carbohydrate solution. This would probably work for most people. However, let’s say you also ingest a portion of Cliff Bar or Power Bar containing 200 calories that hour. You would still have to factor this into your total consumption. Instead of 140 total calories you now have 340 calories, taking your carbohydrate concentration to 16%. If you repeat this hour after hour, you may run into trouble.
Personally, I treat my calorie needs and hydration needs as two separate entities. For hydration I only use water and for my calorie and electrolyte needs I use E-Gel. Let’s say that it’s a really hot day. Although my calorie needs will remain about the same, I’ll have to drink more water to stay hydrated. If I depended on a carbohydrate drink for my fluid needs, then I would risk the chance of exceeding what my body is capable of processing (calorie-wise) and potentially go into gastrointestinal distress.
Other Factors to Consider
First, each sport will influence how many calories you process. Running for example, creates a bigger challenge when trying to ingest calories since you have the repetitive pounding to jar things up a bit. Cycling creates less of an issue. So, you need to treat your calorie intake different for each sport. Second, dehydration significantly contributes to inadequate stomach emptying. Third, the type of carbohydrate (monosaccharide, disaccharide, polysaccharide) will impact how quickly they enter and leave the stomach. Fourth, adding fat or protein will also slow down your absorption rate. Finally, your intensity will impact your ability to absorb the amount of calories you ingest.
Don’t let the lack of a nutrition and hydration plan on race day be your downfall. Practice your race day plan during training so that you approach the start line with confidence, knowing that your rate of intake has been perfected. If you wait until race day to test out your plan, you are taking a big risk.