Hydrate with water and sports drinks.
Wilson recommends water with added electrolytes or low-sugar sports drinks as your most solid hydration options. The key is finding a flavor you like, and mixing it up throughout the day if necessary. This will spice up your routine and give it more variety, so you’ll be more likely to stay properly hydrated.
Skip fried foods.
This should be a no-brainer, but many people may not realize just how detrimental fried foods are to the endurance athlete. Fried foods aren't just high in fat and calories, but depending on what's being fried, most have almost no nutritional value. Pair that with their trans-fatty acids and the risk of increased blood pressure—and there is no reason to "reward" yourself with fried food if you’re serious about training.
Beware of energy drinks and bars.
While they are marketed as nutrient-rich snacks—or even as meal replacements—most protein or energy bars are essentially candy bars (high in fat and calories) with sport-specific packaging. (Take this edible oxymoron, the Snickers Marathon Bar, for example: It has 7 grams of fat and is loaded with sugar.) Same goes for energy drinks. Many of them include high amounts of sugar and caffeine. While you'll get that short-term boost, the crash will slow you down, so Wilson suggests exercising caution.
Set your race-day plan early.
As you start to follow these other Ironman nutrition rules, you should begin to figure out what your body needs (how much water, how many calories, etc.) to perform at its best—so use that knowledge to create a race-day fuel plan that starts up to 24 hours beforehand and runs through the daylong race. You’re definitely going to need carbs to burn during the grueling bike and run, and accessibility and portion-size will obviously be key. Wilson recommends a good ole’ peanut butter and jelly sandwich on whole-wheat bread or smaller snacks, like Clif Shot Bloks and Sport Beans.