Carbs and Endurance Athletes

The use of high carbohydrate diets, as well as supplementary intraworkout (or competition) carb intake, is popular in athletics. This is particularly true considering endurance sports. 

The major objectives with this practice are twofold.

• Provide ample carbohydrate in the diet to (relatively speaking) rapidly replenish glycogen stores and optimize recovery for the chronically training athlete.
• Spare stored glycogen during training and competition and thus stave off fatigue in order to maintain high output capacity.

There is very little argument that this approach enhances performance for most athletes (we’ll dive more deeply into this later) but there exists considerable controversy if carb-intensive fueling is ideal for long term health.

I’m talking about this subject today as I’ve been asked to comment by a number of community members in The Lifetime Athlete App, and because this is a topic of interest to me. In fact, if you like taking deep dives into the science of performance and longevity, and fine tuning your training and lifestyle to get your best results, you might be interested in downloading The Lifetime Athlete App and becoming a subscribed Member of our nationwide Training Tribe community.

You are probably familiar with the relatively new practice of “training the gut” to accept and utilize high(er) levels of intraexercise carbohydrates. This is now quite common in events which require relatively high, sustained outputs such as the Tour de France or Ironman Triathlon. Years ago, it was suggested that these types of endurance athletes could and should ingest 20-30 grams of carbohydrate per hour during training and competition. Now that number is as high as 180 grams per hour.

This project was sparked by a video recently put out by 2017 ITU World Champion and world class triathlete Lionel Sanders entitled “Breaking the Cycle of Bad Eating and Poor Sleep.” I found this video extremely informative and I really appreciated Mr. Sander’s candor. 

With a bit of respectful paraphrasing, I can provide some bullet points on the video.

• Sanders stated that he had gotten used to feeling horrible all the time when he trains, perhaps for 5-6 years.
• At age 37 he reported very poor sleep, often waking as much as 8 times in the night to use the restroom.
• After developing a chronic cough, he sought medical assistance and got bloodwork done to explore these symptoms. This revealed an HbA1c of 5.9%, which is a level considered to be prediabetic.
• Sanders would frequently have intense cravings in the middle of the night and get up to eat granola bars and candy. He talked about the “slippery slope” practice among elite endurance athletes to slam carbs before, during, and after exercise in order to keep up with the extensive energetic demands of sport.
• He described his diet primarily as consisting of convenience and processed foods, low in nutrients and high in sugar and calories, for potentially 2 decades.
• On long training days Sanders would consume over 1000 grams of carbohydrates per day, equating to more than 2 pounds of sugar daily.
• After wearing a continuous glucose monitor (CGM) and making some dietary adjustments including mainly whole foods and more strategic intraworkout fueling, Sanders has been able to normalize his blood sugar and restore his health. He is now sleeping much better and noting improved recovery from training.
• The new training diet is more strategic, with more calories (than before) earlier in the day to help avoid the huge dinners and late night snacking. 
• Intra and peri-workout fueling has been adjusted to reflect intensity, with relatively more carbohydrates consumed during and around higher intensity sessions, and less for low output workouts.

First off, I think everyone should be grateful to Mr. Sanders for being so frank and sharing his personal health information so that we could learn/benefit from it. His openness should be recognized. Next, we must acknowledge that this guy is definitely a “1-percenter” in that he represents the pinnacle of athletic ability/accomplishment. We have to be careful making comparisons and generalizations when we’re talking about a guy who has won 4 Ironman distance races and (I believe) over 30 events at the 70.3 distance. He is among the leanest and fittest. In all probability, most of us would struggle to swim, bike, or run at his race speed for more than a few minutes at best. 

All of the preceding information allows us to open the can of worms regarding the practice of high carbohydrate fueling in athletics. There will be those who will just say you should eat a low carbohydrate diet and this won’t jeopardize your health with respect to the cascade of insulin resistance and blood glucose levels. That may be true but it won’t support the elite level of performance we are discussing. Allow me to explain. 

The first thing we should consider is there is never a complete separation between fats and carbs as metabolic energy substrates during exercise. At the lowest intensities, you’ll primarily oxidize fat (this is also dependent on fitness level) but there still will be some carb burning. And at the highest intensities, carb consumption is prioritized but a small amount of fat oxidation still occurs. There is a metabolic condition known as the crossover point when the body shifts its emphasis from fats to carbs as intensity goes up. 

We can start with the low carb or ketogenic athlete, meaning those who train and compete using a higher fat diet and if they ingest carbs, they do so at much lower levels than that described by Sanders. It’s good to recognize that there is no such thing as a blood glucose level of zero. This would constitute death. The brain and red blood cells need some glucose, and our bodies can make it through glycolysis (although in the keto state glycogen stores are lowered) or gluconeogenesis if we don’t have any carb intake. 

You can stay in the fat-burning zone if your intensity is relatively low and effort is very easy. For most Lifetime Athletes this is Zone 1 and potentially the lower end of the Zone 2 range. You can use fat for fuel and rely on your ample (even in lean individuals) adipose tissue stores. You also have enough mojo in the tank for one or a couple of short, hard bursts. If those bursts only last a few seconds, you can utilize the creatine phosphate (or phosphocreatine or phosphagen) system, and you’ll be fine. But if you need a max output of a minute or two, you probably only have one good one in the tank. So when you look at it this way, long/easy workouts don’t require much in the way of carbs on board, and a few quick outputs don’t either. 

However, if performance requires multiple bouts at very high (anaerobic) intensities such as most stop and go sports, or (importantly in this discussion), sustained outputs at moderate intensity, things look different. These efforts are sometimes classified as high aerobic or sub-threshold (just below the anaerobic or lactate threshold) and they require a steady trickle of glucose if they are to be sustained longer than perhaps an hour. Remember we’re talking about all-day triathlons and bike races here. 

This is where the science of athletic performance has evolved to understand the carbohydrate fueling mechanism very well. The objective is to eat enough carbohydrates in the diet to support recovery and glycogen resynthesis and to maintain an intra-exercise intake that nearly matches the energetic demand. In this manner, the body does not become significantly glycogen-depleted (which drives fatigue and signals slowdown) and can thus maintain high output for hours on end, as long as the individual is highly trained. 

But it is here that things get complicated. Intra-exercise fueling is a bit different from daily diet. During exercise, you want rapidly absorbed (high glycemic), simple carbohydrates (for the most part). Research shows that these carbs are quickly and directly taken up by the working muscles via glucose transport mechanisms unique to the exercising state. This makes sense from a design standpoint and it’s also where the trend to train the gut to accept higher levels of carbs, up to or close to the burn rate in context, has become popular. When you get this right, there is almost no negative impact to long term blood glucose levels because of this muscular disposal rate. 

In this situation things get even more tricky and the proverbial slope becomes slippery. You don’t want to consume more carbs than you need, and you definitely don’t want to do this chronically. Doing so long enough will begin to increase insulin resistance and resting glucose levels, much like what Sanders experienced. That starts a sequelae of poor health consequences driven by hormonal imbalance and metabolic dysregulation. It can become a glucose-insulin-cortisol-grehlin rollercoaster.

Just through observation, in doing work in human performance for over 40 years, I came up with a term about 10 years ago that I call “The 30-year Rule.” It relates to what I’ve seen in many people, including myself, with standard American diet (SAD) consumption/indiscretion. Human metabolism is incredibly durable. You can throw garbage at it frequently and it continues to bounce back, recover, and normalize…for about 30 years. Then it breaks and all the aforementioned negative impacts occur. For Sanders, that happened in only 20 years because of his accelerated consumption patterns compared to the norm.

One of the big problems in this discussion is the very nature of processed carbs. They are engineered to be hyperpalatable and addictive. Big Food pays biochemists and marketeers very well to design this stuff to support corporate monetary incentives as opposed to population health. It’s very easy to fall into the “over-carbing” trap. We get used to the taste, texture, and buzz (and eventually the crash). Our metabolisms become dependent on the fix. Big time. There is the potential for the term sports nutrition to connote poor nutrition if things get out of hand. 

As I move toward summation, I have several points which are pertinent.

• In and of themselves, carbs are not evil. They are just a macronutrient. The manner and quantity in which we consume them is entirely dependent upon the context of the individual athlete. Carbs need to be consumed strategically. 
• Performance and health are related yet not synonymous. As performance goes higher and higher, it becomes increasingly challenging to maintain optimal health. I do not view this as an absolute impossibility but many peak performers exist on the precipice of compromised health. This certainly can and does involve diet, but in a more global sense it is the exposure to very high levels of inflammation. Diet contributes to this but so does training, competition, injury, and suboptimal recovery.
• No matter who you are, insulin sensitivity tends to decrease with age. The diet that worked, or that you “got away with,” at age 20 might not be ideal at age 40 or 60. In this manner, carb tolerance usually declines.
• It’s entirely possible to be fit but unhealthy, and this can be true across almost all sports, not just endurance athletics. If our goal is the long game, meaning the long healthspan in which we preserve wellness through a high-performing lifespan, we need to adjust our training patterns appropriately. 
• Sanders’ example is an extreme yet very good one. Athletes at his level (the pinnacle) do require more carbs, but as he indicates, even that can become excessive. One of the problems as I see it is that many recreational athletes somewhat innocently emulate elite athlete patterns in diet more than in training. They become almost delusional in that they are not training hard for 6 hours a day like a professional, yet they pound carbs to the same extent, vehemently justifying that they “need” them. You might not need as many grams of carbs as you believe or are taking in on a daily basis. Don’t shoot the messenger. It’s just a wakeup call for which we must thank Lionel Sanders.

Here’s the pun of the day. There’s a sweet spot for carb consumption in every Lifetime Athlete. It differs from athlete to athlete based on genetics and specific sports. And it is dynamic within the individual depending on age, gender, and training level. You can benefit from appropriate carbohydrate fueling in endurance sports. And in LIFE.