The biggest issue we have with the notion that “more carbs = better performance” is that there is precious little to back it up, aside from limited scientific evidence and, mostly, rumours and anecdotal evidence from cyclists in the professional peloton. There is no proof provided by any of the pro teams that these cyclists are following this excessive carb/calorie intake fueling protocol. More to the point, what the pro tour cyclists are supposedly doing fuel-wise should not be anything that real-world athletes, like the rest of us, should want or try to emulate. Why would we look to a group of young, genetically gifted athletes who eat, sleep and train for a living and assume that what they’re supposedly doing will work best for us?
Questionable science: Many of the studies used to support high-carb fueling are funded by industry groups. One key figure, Dr. Asker Jeukendrup, helped popularise the 2:1 glucose-to-fructose ratio, which was quickly followed by product launches from companies tied to the research.
Weak performance data: In all of Jeukendrup’s “multi-carb” studies, the athletes were exercising at such a relaxed pace—certainly nowhere near what the pro peloton cyclists are—that they were able to consume more carbohydrates than normal. Unfortunately, even at such a low rate of intensity, many athletes still experienced gastrointestinal distress. Additionally, a well-known study promoting 90g/hr. Carb intake showed that only half the athletes could even finish the 205-minute test. And they were exercising at just about 50% of their maximum output—a very relaxed effort by endurance standards. The question is: “What would happen if the intensity of exercise increased to even a moderate intensity rate/pace?” According to exercise physiologist Dr. Carl Foster, “The frequency of abdominal complaints and symptoms during high-intensity or competitive exercise (Brouns et al., 1987) suggests that attempting to feed while the gastric emptying rate is suppressed by high-intensity exercise may be inherently futile.” In other words, the gut works hard enough to process calories during exercise. Trying to consume more calories—in the hopes of replacing what you’re burning in equal or near-equal amounts—places a tremendous burden on the gut, which will always result in unpleasant, performance-inhibiting, or ruining issues.
High GI risk: The “superiority of multiple carbohydrates” argument is based on the fact that glucose (including maltodextrin) is absorbed by one transporter (SGLT1) and fructose by another transporter (GLUT5). The issue with that is osmolality (never mentioned in any of the studies). When you combine simple sugars and complex carbohydrates, as some of these other companies’ fuels do, the mixture’s concentration and osmolality change dramatically to the point where neither carbohydrate source is digested efficiently. That’s why, despite claims of better output, real athletes are reporting the opposite—GI distress, diarrhea, etc. These issues become more severe in efforts lasting longer than 2–3 hours.
Gut training isn’t working: It would certainly seem right from the start to be unnatural to have to “train your gut to take on more than it’s capable of,” yet athletes are encouraged to ramp up gradually (60g → 70g → 80g → 90g/hour). However, most can’t get past 60g/hour without problems. The “gut training” model overlooks the body’s natural limits on carb/fructose absorption.
Metabolic consequences: High-carb intake (i.e., excessive amounts of calories) suppresses the body’s ability to use fat as a fuel source. Given that nearly two-thirds of one’s energy will be naturally fulfilled via the calories from fat stores during 2+ hour bouts of exercise, consuming an excess amount of carbohydrate calories severely limits—oftentimes even shuts down—the ability to tap into your most abundant, efficient fuel source—fat.
We’ve seen this before: Back in the 1980s, athletes were advised to consume 400 calories per hour using sugary drinks like Gatorade. This resulted in many athletes experiencing GI distress and poor race performance. The high-carb trend is repeating itself again, with similar performance-inhibiting and ultimately ruining results.
Our take: Less is Best! The goal of caloric intake is to consume the least amount necessary to maintain energy levels at the desired level, hour after hour. For the majority of athletes, this represents an intake of ~1 calorie per pound of body weight hourly. And if you find that’s not quite enough calories, that’s a quick and easy fix—you simply consume a few more. Remember, it is ALWAYS easier to fix a “not enough” problem than an “uh oh, I overdid it and now my stomach is rebelling” problem. Fuel with just enough clean, efficient complex carbs to support effort, without shutting down your body’s natural energy systems. Burn fat, enjoy consistent energy, and avoid energy crashes while staying strong for the long haul.