High Carbohydrate Athletic Fueling. A Fad Metabolic Dumpster Fire, Part 1

BY DR. BAYNE FRENCH

Tell Me Something I Care About: 

• The evidence behind these recommendations is weak. What are not weak however, are the myriad detrimental metabolic and health consequences of these recommendations. 

• What you can and will learn, if you can keep your ass in a chair for 10 minutes, are that these recommendations are actually incongruous with peak performance, and dramatically unfavorable if avoiding disease is on your to-do list.  

Dumpster Talk: 

I spent a long time on this article. Most of it was in search of a catchy word for the title. I considered words like fallacious, unsubstantiated, lunacy, shit-show, balderdash, immoral, biased, dangerous, and gobbledygook. Some of these just did not fit. Others were too difficult for me to pronounce.      

I settled on dumpster fire, because I love the smell of burning trash. And it’s descriptive of the health mayhem that occurs over time should you choose to employ high carbohydrate fueling.  

As you hang on my every word, I wish to do the following:  

• Explain the basis for the current fad recommendations of high carbohydrate consumption for endurance fueling. 

• Review biochemical and metabolic pathways that we all possess.  

• Explain how and why high sugar fueling is so unhealthy.  

• Offer much healthier fueling options that I believe improve performance and increase career longevity.  

High Carbohydrate Fueling: 

We have no nutritional requirement for carbohydrate.  I really don’t care if you believe me. Or if you think I’m “unscientific”, or are “disappointed” with my writing, as some have expressed (I am always trying to get better though).   

This is not true of fat or protein. If we do not eat these we die. The healthiest and leanest patients I see do not consume carbohydrate as a staple. The healthiest athletes I see in my practice fuel with modest amounts of carb that is not sugar, and only with heavy, longer training sessions and competition. They are able to access fat for fuel and the generation of our coveted energy molecule ATP. More on this later.  

Intense and prolonged endurance pursuits on the regular are relatively new in our human experience. In a way, it could be considered unnatural. We are of course engineered for movement:  lifting, traveling, and fighting, all the while procreating, but strenuous and repetitive activities (when conservation of energy was vital for survival) is new. Given that, nutritional requirements are different for those with a proclivity for endurance suffrage, as they would be for others. 

There are outliers, like truly high-level, “fat adapted”, competitive athletes that do not fuel with carbohydrate. Later will be an explanation of the work of Dr. Volek with these athletes. Then there are others, in the middle (like me, minus the “high-level”). I have known the joy of obstacle course racing podiums. I even won prize money, which was enough to buy my fishing license for the year. For long training sessions and competition, I fueled with carbohydrate but never in large amounts.   

Most people and especially athletes are not fat adapted. They simply do not burn fat for fuel very well. This is probably you. Like a foreign language or pinochle, we can learn to become efficient burners of fat. Until this glorious day comes, the adage Carb is King rings true. I mean that most people will do better, most of the time, fueling with carbohydrate.   

The difficulty arises when we ask how much carb and from what source?   

There are also many circumstantial issues to consider like body size, event duration, ambient temperature, and whether the competing individual is a beer- drinking, bread-eater or more metabolically efficient and fat adapted in their daily life. What are your goals with competition? Just to finish, or to try to win? 

It becomes exceedingly difficult to make accurate blanket statements, and in fact irresponsible to imply that since some is good, more must be better. 

The More is Better concept has permeated human thinking for generations. Current fad fueling recommendations are just an extension of this mindset. But is it valid in regards to athletic performance? Dr. John Smith thinks so.  

In 2010 Dr. Smith studied 12 (twelve, not twelve thousand) high-level cyclists and found that there was a dose-response relationship with the amount of glucose ingested and performance (Smith et al. J Appl Physiol. 2010).   

In 2013 he led a slightly larger study of 51 triathletes and cyclists. Twelve different beverages were used and the participants were blinded as to what they were consuming. Not blinded like their eyes were gouged out, but that they didn’t know what they were drinking. Again, the conclusion was that the higher the carb intake, the better the performance (Smith et al. Med Sci Sports Ex. 2013).    

Autonomic Dysreflexia: 

Can we just step back a moment and think about this? The improvements in performance in Dr. Smith’s studies were minimal. The sample sizes of studied participants were quite small making it very difficult to assign any statistical significance or power to the findings.   

These athletes were not followed over a prolonged period of time in a longitudinal manner looking at performance. Nor were GI distress, career longevity, number of injuries, percent body fat, cancer and heart disease incidence studied. More on this later. 

Consider this. When human mammals, including well-conditioned athletes, consume large amounts of sugary crap, their blood sugar increases. The body knows this is a toxic situation and releases stress hormones like cortisol and epinephrine (adrenaline). Perhaps this “fight or flight” response is responsible in part for the modest increase in performance. 

This stress response has been reported in Paralympic athletes that intentionally cause bodily damage leading to the neurological response of Autonomic Dysreflexia, or colloquially as “boosting”. According to a CBC News article in 2012, this illegal practice can consist of “sitting on pins, cracking toes, twisting scrotums”. The stress response can lead to enhanced physical activity, conferring a small advantage, yet obviously antithetic to health.  

The blood sugar spikes that result from high carb fueling evoke a similar physiological response.  

High Sugar Fad Recommendations: 

A few companies and their vocal mouthpieces are currently making recommendations I consider harmful, on how much carbohydrate athletes should be consuming per hour. These guidelines are not based on powerful studies, meaning a large number of people were not followed over the course of many years. Nor are these recommendations based on any semblance of healthful action.  

We do have a storage form of carbohydrate called glycogen. Intense exercise lasting about an hour or two is usually well fueled by this stored carbohydrate.   

According to one high carb fueling author, “30-60 g of simple carbs per hour” is needed for intense exercise lasting 1-2 hours. I agree with this, and feel that this level of carbohydrate consumption is well substantiated by decades of research and experience, but regardless of the exercise duration.

This author goes on to recommend that for intense exercise over 2 hours, 60 to 90 g of carbohydrate per hour is needed. On what basis? 

Author Andy Blow states:  “This is where ‘multiple transportable carbohydrates’ (MTCs) such as Glucose/Fructose blends can often be preferred in order to help to maximize absorption of very high amounts of carb via your gut. MTCs are a fancy way of saying different sources of sugar.”  

The Gatorade Sports Science Institute (GSSI) recommends that in the 24 hours prior to hard training or competition athletes should consume 7-12 grams of carb per kilogram of body weight. Let’s do some math… for a 150-pound athlete that is 477-816 grams of carb. That’s equivalent to about 50 slices of bread. Who are these people? Honestly, your health depends on you shucking this advice like a sugary crap cloak.  

Gut Training?: 

Your gut flora has an orgy when it sees lots of carb. There’s fermentation and methane production and other microbiological happenings that just stink. Seriously, open a window AND turn on the ceiling fan.  

There are now high carb fueling terms for this:  Exercise-induced gastrointestinal syndrome (EIGS), and Exercise-associated gastrointestinal symptoms (Ex-GIS).  

You:  “Earl, my God man, did something die inside you?!”     

Earl:  “Sorry fellas, that’s my Ex-GIS acting up”. 

You:  “Chet, there’s literally a blue haze behind you! Do NOT run past an open flame dude!”                      

Chet:  “Yah, I got a bad case of EIGS”.   

Perhaps we could “train” our intestine to not react to so much ingested carb. It’s worth a try because sugary crap tastes yummy. There’d be no shortage of American volunteers for this study.  

Martinez et al (Sports Med. 2023) performed a Systematic Literature Review on “gut-training”. 304 studies were reviewed and 8 were considered appropriate for inclusion. It was found that with a 2 week “repetitive carbohydrate feeding protocol” (i.e. sugar stuffing), gut discomfort and carbohydrate malabsorption reduced considerably. Significant improvements in upper (ralphing) and lower (toots) symptoms were observed. Strong work everyone, we all need to do our part to protect the ozone layer. 

Again, can we just rationally think about this for a moment? Competitive eaters gorge to stretch their stomach, and to neurologically blunt a vomiting response. Neither form of “training” has a semblance of health, disease prevention, or longevity inherent to it.  

Asker Jeukendrup PhD seems like a pretty smart guy. He published an article Training the Gut for Athletes (Sports Med. 2017). The details of sugar absorption from the intestine into the blood stream via “transporters” were discussed.  There are specific transporters for glucose and fructose.  It was shown that by trying really hard, and consuming large volumes of sugary crap, the number and efficiency of these transporters could be enhanced. The hopeful results being less toots, more sugar in the blood stream, and better performance.  

Dr. Jeukendrup seems to agree with “current guidelines” to consume 60 g of carbohydrate per hour for exercise duration lasting up to 2 hours. Above 2 hours, up to 90 g per hour. Why? Interestingly the article was published with support by the Gatorade Sports Science Institute, a division of PepsiCo.  

I have no respect for performing studies, funded by sources that sell products the studies are designed to support. To say nothing of the potential future liability issues associated with promoting the consumption of large volumes of a toxic substance (sugar) that drives the formation of cancer, cardiovascular disease, obesity, diabetes, and Alzheimer’s disease. That is not a legacy I would want.  

The Opposite of High Carb Fueling: 

Dr. Volek et al. performed the Fat Adapted Substrate Oxidation in Trained Elite Runners (FASTER) study that was published in Metabolism in 2016. The purpose was to study the extent of metabolic adaptations and differences between high-carb eating athletes and low-carb, high-fat eating athletes. 

It involved 20 elite ultra-marathoners and ironman distance triathletes, all in “racing condition”. Over half of them had sponsors, a third of them had course records, a fourth of them participated for Team USA, and some with national and international records. Basically, they were a group of super scary individuals. Through an extensive interview process, 10 carb eaters were found (carb:protein:fat ratio being 59:14:25) and 10 fat eaters were found (10:19:70). The two groups were very closely matched in every other category except diet and fueling practices.  

The low-carb group consumed 6-times less carb during the course of an average day than the high-carb group (82 vs 684 g/day). What is very important to understand is that the low-carb eating athletes had been doing so for an average of 20 months, thus considered well adapted.  

Despite the two groups being considered closely matched, there are some interesting small differences between them. HC is high-carb and LC is low-carb: 

                                    HC                    LC 

% body fat                  9.6                   7.8 

Lean mass, kg            57.3                 60.9 

Fat mass, kg               6.5                   5.5 

VO2 max                     64.3                 64.7 

From the above data you can see notable differences in body fat percent and the amount of muscle the athletes possess.  

The ability to burn fat was 2.3-fold higher in the low-carb group (1.54 g/minute vs 0.67 in the high-carb group). Despite the marked differences in fuel usage there were no significant differences in resting muscle glycogen, exertion related glycogen depletion levels, and glycogen re-storage levels in recovery. Restated, the low-carb athletes possessed an extraordinarily high ability to burn fat but exhibited the SAME ability to break down stored carbohydrate, and build back those stores as the high-carb athletes.  

Several previous studies however did not show preserved glycogen stores in low-carb athletes (Phinney et al. Metabolism. 1983; Helge et al. J Physiol. 2001; Zderic et al. Am J Physiol Endocrinol Metab. 2004). These studies in general studied athletes consuming low amounts of carb for a much shorter period of time, indicating that the cellular mechanisms and metabolic pathways involving glycogen preservation and restoration make a longer time. Ample adaptation takes a least several months, not weeks.  

Author Dr. Volek likened the muscle glycogen responses in the low-carb athletes to that of “Alaskan sled dogs”. These animals have tremendous endurance abilities and have been shown to maintain their glycogen stores despite running 160 km per day for 5 days and eating high fat and only 15% carb (McKenzie et al. Med Sci Sports Exerc. 2005). 

For the first time, the FASTER study showed that well fat/keto-adapted endurance athletes possess a dramatically enhanced ability to break down and burn fat while maintaining normal muscle glycogen. Dr. Volek states “Keto-adaptation provides an alternative to the supremacy of the high carbohydrate paradigm for endurance athletes”.  

Summary of the FASTER study benefits of fat-adaption and ketones summary: 

1. Fat is considered a more efficient fuel. It is over twice as energetically dense as carb and protein. (1 gram of fat possesses 9 calories, 1 gram of carb and protein 4 calories). Furthermore, fat is stored in an anhydrous manner, meaning it is not linked with water.
   
   
2. We possess a massive depot of fat storage (50-100,000 calories). Carb stores in the form of glycogen are meager (less than 2000 calories).
   
   
3. Ketones are made when fat is burned. Ketones reduce oxidative stress. Exertion results in a huge increase in mitochondrial-induced free radicals. Ketones cause an upregulation of antioxidant pathways (Histome deacetylase inhibitor) to reduce these free radicals and oxidating stress/damage.
   
   
4. Ketones are anti-inflammatory and reduce inflammatory compounds like IL-6, IL-8, TNF-alpha. Other markers of inflammation like white blood cell count and c-reactive protein (CRP) are reduced in a higher ketone environment.
   
   
5. Observed (but not measured) enhanced recovery. This is largely anecdotal but certainly has biochemical merit given reduction of pro-inflammatory compounds and enhanced ability to reduce free radicals.
   
   
6. Reduced “bonk”. The dreaded bonk is an energy crisis occurring in muscles and the brain. Ketones fuel the brain readily, and ketones and fat fuel skeletal muscle efficiently and basically never run out. There is a direct linear relationship between blood ketones and brain ketones.
   
   
7. There is absolutely no question regarding the ketogenic diet’s ability to assist with weight loss. This improved body composition has direct impacts on the power to weight ratio.
   
   
8. Enhanced career longevity. Animal models (Roberts et al. Cell Metabolism. 2017) have shown extended longevity and “healthspan” in animals eating a higher fat diet. Again, there is much that makes sense here. Slow accumulation of fat tissue around the midsection directly compromises power to weight. Oxidative stress and inflammatory compounds result in metabolic consequences over time, increased soreness, and potentially impaired performance.

Click here to read Part 2