Sifting the wheat from the chaff: Hi-Carb Fueling

We are constantly being bombarded with new content related to training techniques, supplements, new equipment, etc. So much content is then copied and reposted by new sources and suddenly it becomes conventional wisdom or accepted truth. Often important aspects of these topics get lost or under-emphasized.

This post will be the first of a series where I will attempt to distill various topics to the important takeaways. Today's topic, Hi-Carb Fueling, has been trending this year and I receive posts on it from new sources weekly. I wanted to start with this one because I feel the repeated content has been focused on the fueling habits of the professional peloton without any major focus on how to scale their numbers to other levels of competitors.

Hi-Carb fueling is LEGIT!

Proper fueling matters and perhaps this trend is merely confirmation that most people tend to under-fuel their riding. During my decades of training and racing I have experienced dozens of bonks and have become intimately familiar with the signs of low fuel. You simply cannot maintain optimal output if you are not properly fueled. Of course, if output is low enough, you can get away with fat as your primary fuel. However, even at very low outputs you will burn carbohydrates and at some point you will deplete muscle glycogen and liver stores and need to consume additional carbohydrates.

Despite your ability to ride long and slow on fat, if you want to "go hard" you need carbohydrates as your fuel. While riding at FTP the muscles are fueled almost 100% by carbohydrates. Even at your so-called FatMax pace (output that achieves the greatest fat burn in calories/hr; top of Zone 2 for most people), you are still relying on up to 50% carbohydrates for active fuel.

But, you don't need to consume as much as the pros

Accepting the truth of Hi-Carb fueling doesn't mean all athletes should consume the same quantity of carbs per hour.

A World Tour professional rider generates very high watts and, therefore, burns very high calories to do so. The equations to determine the calories burned while riding at a specific wattage are pretty straightforward. Riding at 200W for an hour is equal to approximately 720 kilojoules (energy). Keeping the math simple, for a human this is basically equal to 720 calories/hr. For me, 200W is a relatively low output and probably fueled by ~50% fat. Thus, I would be burning approximately 360 calories/hour of carbohydrates. Contrast that with a male World Tour professional whose similar relative output (low Zone 2) might be more like 900-1000 calories per hour (450-500 calories from carbs). Clearly, these are different demands from a fueling perspective.

Much of the media is throwing around carbohydrate fueling numbers like 120-150 gr/hr. If we assume these are the right kind of numbers for professionals, we should adjust them to our reduced outputs. I tend to fuel at about 75% of these numbers (90-100 gr/hr is probably enough). How much one should consume is also related to duration and pacing and can get quite complicated (this is something I fine tune for the athletes I coach).

Most people have some limit to how many calories they can tolerate while riding without stomach upset issues. This is the danger of over-fueling and why you want to make sure your intake is appropriate to your output. This is also why you need to practice hi-carb fueling in training so that you dial in your tolerances (and improve them!).