By Jordan Rapp

In tackling the topic of Kona race-day fueling, I expected there to be differing opinions. What I didn’t expect was the extreme intellectual chasm between these opinions. Especially because ideas that are seemingly so different seem to work equally well. Or equally badly. Given the complexity of this topic, I’m going to start with a “formula” (I use the term loosely) that I came up with a while ago to help people who were struggling with nutrition. It’s by no means complete, but this has worked for me, and it’s worked for other people, so I think this is a reasonable place to start. I call it “1-1-1,” mostly because it’s easy to remember. You should drink about one liter of fluid an hour. Less is OK if it’s not hot, but don’t drink too much more even if it is hot. You should eat about 100 grams of calories per hour. Less is OK if you are small, but don’t eat much more if you are bigger. I prefer all carbs, but I’m certainly OK with some of those calories being fat and/ or protein (so-called “mixed nutrient calories”). And you should take about one gram of sodium per hour. That’s it. If you deviate substantially from this, you should probably have a reason, especially if you go over those numbers.

Somewhere around 800 milliliters per hour (I round up to 1 liter per hour for simplicity) is the theoretical maximum as to the amount of water your GI tract can process. You can drink more, but it’s very likely it’ll just flush right through you. At one particularly hot, windy and shadeless race in the middle of the Nevada desert, I drank 20 bottles (about 500 milliliters apiece) over the course of 6.5 hours on the bike. My theoretical maximum should have been 13. I can tell you where those 7 extra bottles went—right through me. Was it bad that I drank that much? It’s not clear. They may have played a role in cooling me down, even if they didn’t help hydrate me. But it was clearly more than I was able to process.

If you find you don’t consume at least 400–500 milliliters per hour of liquid, you’re probably running a greater risk of dehydration than you need to. On the calorie front, there’s a lot more debate, mostly because body size seems to play a bigger role. As does gender, for reasons both related and unrelated to body size. But I’ve never seen anyone recommend more than about 600 calories per hour for a big guy, regardless of how big. Even that can be a struggle. Somewhere under 500 calories per hour seems to be about the limit as to what our bodies can oxidize. If you’re trying for something like a 1000 calories per hour, that’s just way too much. On the low end, it’s really a lot more dependent on body weight (we’ll get into that). But at least 200 calories per hour is a pretty good goal. Unless you are a very small, you need to be getting in at least that much. If you consume fewer calories than that—typically because you can’t consume that many—you’re probably going too hard.

The sodium and overall electrolyte recommendations are the most variable. If you don’t have issues with cramps or your stomach not clearing, then it’s no problem. If you do, this is a reasonable place to start. Now, with the basics out of the way, let’s wade into the details.

Before we get deep into the debate, we need to establish a few facts that are not up for discussion. There are few people who dispute these facts, but like climate change deniers, there is a simple word for them: wrong. Practically everyone in the sports science community agrees that prolonged, strenuous exercise will cause dehydration. This is irrespective of weather conditions. You simply cannot replace everything you are losing when you exercise at a high level. Even in cold weather, you will lose electrolytes and fluid to sweat and metabolic function. And you will use up calories at a greater rate than you can replenish them. These are important facts to understand, because the debate is not about whether or not to replace what you are losing—it’s about how much of what you are losing you should try to replace and how to go about replacing it. Your body is really good at maintaining homeostasis, even in the face of adversity, like Ironman. What you need to do is simply help your body do this. It can shuffle things around on race day to do it, so the key is what is essential to replace and what can you let your body shuffle from one place to another.

We also need to cover some terms. When you are fully hydrated—which everyone can agree is certainly the best place to start exercising—you are said to be in a state of “euhydration.” Dehydration isn’t really specific in a scientific sense, so the more useful term is “hypohydration.” This refers specifically to body fluid losses, which is of course not all you are losing when you exercise and sweat. But this is how scientists measure fluid losses. For example, hypohydration of two percent means you’ve lost two percent of your body’s fluid mass relative to a state of euhydration. “Hyponatremia” is a shortage of sodium in the bloodstream and is a serious, life-threatening condition. Drinking too much can be much worse than drinking too little. Typically, dehydration is self-limiting, at least in a sense. If you are dehydrated, your body cannot function well, and you will slow down, which will help prevent further problems.

The big debate here is really centered on how and how much you should replace. As I mentioned regarding the “1-1-1” plan, there’s actually pretty good agreement as to how much you can replace.

What’s most interesting is that in spite of the disagreement on how much fluid, electrolytes, and calories people need to consume, all these approaches to race-day hydration can work for different athletes. Each group seems to think the other is totally wrong and yet both approaches seem to work well for different athletes. As always, it’s remarkable how adaptable our bodies are. My goal here is to give an overview of some of the differing opinions with the rationale and research behind each and then let you figure out what you want to do (or not do) with it. Sometimes, the best thing to do is just change. If you eat solid foods and have trouble, switching over to just liquids may work. On the flip side, if you’ve tried liquid-only and struggle with it, you may want to try solid foods. One thing that’s important to set as a ground rule, however, is that the overwhelmingly most important thing about nutrition has nothing to do with nutrition. It has to do with pacing. How hard you are going plays a huge role in how much and how well you can process what you consume. This is because much—though not all—of this starts with blood.

One distinction that we need to make is that fueling for Kona is different than fueling for other races. The weather in Kona makes a huge difference. In a previous column, I wrote about the importance of heat acclimation. I alluded to the fact that nothing you do on race day can make up for a lack of acclimation. Hydrating and fueling in the heat is much more difficult if you are not acclimated. If you are acclimated, your fueling and hydrating plan should be basically the same as at other, more temperate races. The reason has to do with your blood. When you are heat acclimated, less of your blood needs to be diverted to your skin to cool you off, which means more of your blood can go to your gut. When you are exercising, your blood needs to go three places: your muscles, to provide oxygen and nutrients to your working muscles; your skin, to help cool you down; and to your gut, to help process fluid, calories and electrolytes. The amount of blood your muscles need is basically tied to how hard you are working. The harder you go, the less your gut can process. This is why you probably can’t eat anything for a sprint, not much for an Olympic, you can eat a bit for a half-Ironman, and quite a bit (relatively) for an Ironman. This is also why, if you can’t eat or drink as much as you should be able to, it’s probably because you are going too hard.

Most of the blame placed on the on-course nutrition “just not working” is the fault of people riding too hard. If your gut shuts down, the best thing you can do is to get off your bike and stop. If you stop for 15 minutes, you lose about as much time as you would if you walk (instead of run) two miles. And when most people start walking, it’s usually for a lot more than two miles. If nutrition has been your Achilles’ heel in race after race, the first place to look is at your pacing. Slowing down is the surest path to better success with nutrition and hydration. Heat acclimation will attenuate some issues with pacing, just as it will attenuate issues with fueling, because it makes your body more efficient at cooling itself and at tolerating heat. You sweat more evenly when you are acclimated, but you lose less electrolytes, and you have some other adaptations (like heat shock proteins) that are helpful. Acclimation needs to be done before the race. Pacing is something you have control over on race day. Both are huge assets. I think the importance of these two topics is why such disparate nutritional advice can work so well. If people pace well, and they are prepared for the conditions, the rest is really just details. But details are still relevant, especially for a race as hard and competitive as the Hawaii Ironman.

There are two schools of thought regarding hydration: the “drink to thirst” side and the “drink to a schedule” side. For simplicity’s sake, let’s refer to the groups as “thirst” and “schedule.” Those in support of thirst seemingly got a big boost with a recent study conducted by a group including Paul Laursen, who was the anchor of my piece on heat acclimation. One of the huge issues with any hydration study is that people know how much they are drinking. So Laursen and his colleagues decided to use IVs (hidden from view) to control for this. They had three groups. One group was given enough fluid via IV to remain in a state of euhydration during exercise, one was shortchanged to the extent of about two percent hypohydration (the traditional line at which performance is supposed to degrade substantially), and the last shortchanged to three percent hypo-hydration. Ice cubes and a minimal (100 milliliters) amount of water were provided to offset dry mouth during exercise. They were dehydrated via exercise bikes in the heat and treadmill walks until they hit the target state of hydration. Then they were rehydrated fully, some, or not at all via IV and given a standard meal. After this, they were tasked with a 25-kilometer all-out time trial. The findings? No significant difference between the groups. Some small variance in core temperature (0.3 degrees Celsius on average) was noted between the three-percent group and the fully-hydrated group, but that’s it. Performance was basically the same. Their argument here is that traditional guidelines regarding dehydration have been vastly overstated and that as a result, simply drinking when you are thirsty—relying on your body’s own built-in thirst mechanism—is adequate.

There is a lot more research on this topic, but this study has been generating a lot of buzz. It offers a fair summary of the two sides. One side says that, thanks to evolution and built-in regulatory mechanisms and various adaptations, your body knows what is best. To a certain extent, given that we know dehydration is inevitable, the counter to this isn’t that euhydration is the goal. As we said, it’s impossible to replace what you are losing as fast as you are losing it. Rather, the counter is that to “obey your thirst,” to borrow the phrase, is problematic for a bunch of reasons and that your body doesn’t actually know what is best all the time.

Coming in on that side is Stacy Sims, PhD, founder of Osmo Nutrition. My first question to Sims was, “What about Laursen’s study?” I was guessing that the use of IVs is a potential problem, because processing fluid via the gut and injecting it are not the same thing. She confirmed this. The issue, according to Sims, is that during exercise, 60–80 percent of the blood in your body gets diverted to muscles for energy and to the skin for cooling. That doesn’t leave a lot available for the gut. So one problem is that by the time you realize you are thirsty, your body may not be able to process as much as you suddenly want to drink. By drinking on a schedule, you’re giving your body time to process the fluid you take in. Drinking one liter all at once and then nothing for 60 minutes is not the same as drinking 250 milliliters every 15 minutes. Another problem is that dehydration can compound itself. As your body diverts blood away from the gut, it’s also diverting oxygen. This hypoxia causes changes to the lining of your intestines. This can lead to a breakdown in gut integrity known as “leaky gut,” where your intestines actually become more porous and fluid just sort of goes into your system, but not in a productive way. Think of a leaky pipe leaking water into the walls of your house. So as you get dehydrated, you actually become less able to rehydrate effectively. The problem compounds itself.

Another problem that Sims talked about was the role of the gut in the central nervous system. Outside of your brain, your gut is actually your largest collection of nerve cells. Your gut is almost a second brain, and for obvious reasons: food and water are critical to life. And there is increasing research on the role your gut plays in your overall mental state. Sims extrapolated from this to argue that, as you become tired from racing, your brain is less able to make decisions about things like, “Am I thirsty?” The idea of mental fatigue is significant for a variety of reasons. It’s why course markings that are so obvious the day before a race become so confusing the day of. I figure my IQ roughly halves on race day. It’s easy to forget to eat and drink for a whole variety of reasons. In addition to being dumber, you are also in competition mode, and you’re worried about the course, other athletes and everything else there is to worry about on race day.

Apparently, for women, due to a variety of hormonal factors, the problem is even worse. Women tend to have a more muted thirst response to begin with, according to Sims, and when you add the complications of race day, this effect can become worse. Additionally, races are often held in locations with different weather or other environmental conditions, such as altitude, that can further skew the body’s perception of what it needs. All these factors can be mitigated with acclimation, but only so much. There are just way too many reasons not to trust your thirst response, especially when missing the signs early can make it even harder on your body to process the fluid once you do start drinking.

Sims is a huge advocate of an approach that I’ve taken for a long time, which is that race-day nutrition extends well beyond race day. We agreed that Thursday through Saturday before a Sunday race (so Wednesday through Friday for Kona racers) is part of race day—at least from a nutritional standpoint. You must go into the swim well prepared. For me, that has meant getting at least 1,000 calories in at breakfast on race morning. It’s meant making sure that I’m hydrated, but also remembering that hydration extends beyond just fluid. I don’t want to “rinse” all the electrolytes out of my system.

Drink to thirst is a good idea before the race. Also make sure to get in electrolytes. The six primary electrolytes are sodium (Na+), which is the biggie, chloride (Cl-), which is the other half of salt, potassium (K+), so eat your bananas and drink your orange juice, calcium (Ca+) so eat your yogurt, and then also magnesium (Mg+) and zinc (Zn+). Magnesium and zinc deserve special mention because they are the hardest to get from food, so supplementation is the way to go for most people. Zinc deserves an extra-special mention because it is the only one you should never supplement on race day. Of the six, it’s the riskiest, because it is quite toxic in excessive quantities. You can pop salt pills without much adverse effect, but you should never pop zinc pills in the same carefree manner. As long as you take a multivitamin with 100 percent RDA for zinc, you should be fine. But if you are someone who eschews multivitamins, you may be short on zinc (unless you eat a lot of oysters… or bear meat).

Sims added another caveat on salt, and that’s that being a salty sweater more typically means you consume a lot of salt rather than that you need a lot of salt. She also advocated having a 500 milligrams of Tums in your T2 bag, citing the importance of calcium as an often overlooked electrolyte. Sims added that Tums also has peppermint, which can help with gut integrity by offering a calming effect if your intestines aren’t happy with you.

Overall, Sims emphasized that electrolytes fall into the same camp as water: you don’t need to replace what you are losing. If you are sufficiently loaded up before the race, you only need to replace about half of what you lose. Forty percent replacement can offset losses as high as 80 percent. She said electrolytes, especially sodium, are about transport, not replacement. Your body has lots of stores it can borrow from if you set it up that way. She also added that sodium citrate is preferred for replacement as opposed to sodium chloride. You’ll note that except for chloride, which is important, all of the six primary electrolytes are positive ions. Citrate is a negatively charged molecule that often makes up salts. The exact details of this are heavy biochemistry, and this is already a long topic, so just remember that citrates tend be a preferred salt form for any of the key electrolytes if you’re replacing them via supplementation. One of the best sources for loading up before the race on primary electrolytes in a citrate salt is Osmo’s PreLoad Hydration mix; there’s a version specific to both men and women.

The last topic I discussed with Sims was that of calories. Until this point, my own experience matched her research pretty closely, but here we start to diverge a bit. We agreed that the tipping point on nutrition happens somewhere between 70.3 and Ironman. Nutrition is clearly a major issue for racing Ironman. It is, without question, the fourth discipline. At 70.3, especially for pros racing only four hours, you can get away with a lot more. When the day gets longer than that, your body is much less forgiving of nutritional mistakes.

Intensity also becomes a bigger factor. A pro racing for eight or nine hours is obviously going harder than someone racing for 14 or 16 hours. At higher intensities, because more blood must go to muscles, less can go to the gut. The legendary Bob Babbitt recalls eating a cheeseburger en route to his finish in the first ever Ironman Hawaii in about 15 hours. And you can do that. I see people pulling PB and J out of their special needs all the time. I could imagine eating a PB and J during training, but no way that I could do it at race effort. But if your race effort is a lot more like your training effort, then by all means, PB and J it up. For me, I’ve had the best success with 100 percent liquid calories. And this is more typical rather than less typical among pros. I don’t know of any pros that eat real food. Gels are more common than bars. Likewise the new “blocks,” basically gummy snacks, are also popular. But it’s all about sugar. Typically, it’s sugar spaced out pretty evenly over the race.

Most common is the simple-to-follow rule: “eat/ drink every 15 minutes.” Robert Kunz, cofounder and VP of science for First Endurance, falls more into this camp. (Full disclosure: I have been a sponsored athlete of First Endurance since 2009.) Sims promotes “food” for calories, separating it from the liquids and, to a certain extent, treating these as separate entities. The type of food changes somewhat based on intensity (i.e., simpler foods with a higher carbohydrate proportion for higher intensities, more complex foods with more mixed macronutrients for lower intensities). But she believes everyone can benefit from mixed macro-nutrients during racing.

Sims describes her approach as “hydration in the bottle and food in the pocket.” Calories and electrolytes are important components of hydration, but only in so far as they help absorption. Pure water is not as easy to absorb as a drink with some sugars and some electrolytes. This gets into the topic of osmolality, which is at the heart of this debate. Osmolality is the number of osmoles per kilogram of solvent (this is another heavy concept—basically just think of it as one osmole equals one molecule for our purposes here). Blood has a typical osmolality of 270–300 milliosmoles per kilogram or 282–292 milliosmoles per liter (of water). If a drink is roughly equal to that, it’s called “isotonic” (some Europeans refer to electrolyte drink as “iso,” which is why you might hear a German guy yelling for this at an aid station). A drink with fewer osmoles is hypotonic. One with more osmoles is hypertonic.

Sims says that the body prefers a hypotonic solution just over 200 milliosmoles per kilogram. This is why Osmo is relatively dilute. It’s mostly water, with just a little sugar and electrolytes to help transfer across the small intestine. On the food side, she advocates bars, especially fruit/nut/seed bars like the Clif ZBar or the Pro bar, and blocks and chews. Though what you eat also depends on when you eat it. Sims recommended solid food for the first half to three-quarters of the bike ride. On the run, she likes blocks for the first third, blocks and a simple glucose source for the middle third, and then very simple sugar (like coke) for the last third. In terms of quantity, 3–3.5 calories per kilogram of body weight every hour. On the run, it’s 2–2.5 calories per kilogram each hour. But that’s only counting the calories in your food. Sims doesn’t count the calories from the sugar in Osmo, for example (which works out to roughly 150 calories per liter). If you add those calories in, it starts to look a lot more “normal” in terms of what I see and recommend and what I do myself.

My own approach, shared by Kunz, is that you want to be as steady as possible in all aspects. Kunz agrees on the importance of osmolality, but disagrees that you can consider what you drink and what you eat separately. At the heart of this disagreement is, I think, some background. Kunz is, like me, a triathlete by preference. Sims’ roots are in the cycling world. Kunz and I both agree that cycling, where races are typically punctuated by shorter periods of high effort (climbs and breakaways) and longer periods of low effort (drafting in a peloton) works well with a food-and-water approach. This is why cyclists eat real meals, like sandwiches, during Grand Tour stages. But Ironman isn’t like that. Ironman should be a steady effort. You don’t want periods of high effort and periods of low effort. You want a long period of relatively consistent effort. We both believe this favors a different nutritional approach that more closely mimics the effort being put out.

When designing the new EFS-Pro drink, the goal was to create a high-calorie drink with a relatively low osmolality. EFS has always been a relatively high-calorie drink, giving close to 200 calories per bottle and lots of electrolytes. The goal with EFS-Pro was to give even more calories at even lower osmolality by using more complex carbohydrates for more calories per osmole. EFS-Pro uses a starch called amylopectin, which has a lot of calories per molecule, meaning you can get more calories at equivalent osmolality to something with simpler sugars, or a much lower osmolality at equivalent caloric concentration. EFS-Pro was designed to be both fuel and fluid.

One thing to note is that there is basically no way to get a hypotonic solution that has adequate calories. It just can’t be done (yet). So Kunz and Sims disagree on the importance of tonicity for absorption. But Kunz also disagrees with the idea that you can ever really consume something hypotonic to begin with. He says you have to consider what’s in your gut—meaning both the food in there and the fluid in there. The idea is that anything you consume affects osmolality. According to Kunz, “You cannot isolate hydration from calories. If you consume a [sports] drink and then take even a single salt capsule, you have effectively increased the osmolality. Add a gel and you have significantly increased the osmolality.”

The divergence here comes largely, in my opinion, on the issue of timing. Obviously a bottle of water and a bar separated by an hour is not the same as a bar and a bottle of water separated by minutes. And how fast does this stuff process? Simply put, it depends on you. I think this is at the heart of why such different approaches can work equally well.

Beyond this area of divergence, there was much more convergence, which I think is important to emphasize. Kunz went on to say, “Over the last three to four years, we have come to the realization through anecdotal evidence and athlete testing that most athletes in half-Ironman and Ironman-type racing are attempting to push too many calories. They put too much focus on calories and don’t pay enough attention to the hydration side of the formula. In doing so they are skewing their osmolality so much that those calories and fluids are not being absorbed and therefore their nutrition plan and performance suffers. When they suffer they often feel they need more calories and the cycle begins that causes more and more stomach issues.”

Here you can really see a lot of agreement. Calories are important. Too many is a huge problem, and understanding the math of osmolality can help with this. Both Sims and Kunz recommend a pretty narrow range of calories, and recommend focusing on the fluid component just as much as the calories themselves.

The Ironman nutrition puzzle has three parts: fluids, calories and electrolytes. And now a fourth with osmolality. Too little of any of these is a problem. But so is too much. And what’s pretty clear is that there is more agreement than not on the boundaries in each case. If you’re outside those boundaries, you need to have a reason why. And if you are struggling, trying to figure out where you deviate from these recommendations can help a lot. It’s important to remember that you may be out of whack in different directions. Too many calories and too little fluid seems to be the biggest problem. But don’t forget about too many electrolytes, because of how it affects osmolality. Breaking it down into its various components won’t solve the problem for you—that requires trial and error and probably even more error. But simplifying and segmenting it sure can make it an easier problem to solve.

Jordan Rapp is a professional triathlete and columnist for LAVA.