A Selection Of Fruits And A Bowl Of Oatmeal On A Table

How to Regulate Sugar Consumption Without Compromising Athlete Performance

BY Phil White

Certain athletes could be affected by glucose dysregulation. Learn how you can help them find the sweet spot between consuming sufficient sugar to fuel optimized performance and going overboard into potentially unhealthy territory.

“The beneficial effects of regular physical activity on insulin sensitivity (SI) and glucose tolerance are well documented.” That’s the opening statement in a study by a team of physiologists from the Pennington Biomedical Research Center.[1] They demonstrated how endurance training makes positive changes at a genetic level, with high responders showing double the expression in three genes involved in energy metabolism after training.

However, while your athletes might be experiencing such benefits, some could lessen those gains by pounding excessive quantities of high-carb sports drinks, gels, goos and other supplements. In this article, we’ll explore how certain athletes could be affected by glucose dysregulation and how you can help them find the sweet spot between consuming sufficient sugar to fuel optimized performance and going overboard into potentially unhealthy territory.

Glucose Metabolism

There are two major mechanisms of glucose metabolism: glycolysis and gluconeogenesis. Simply put, glycolysis breaks down glucose into either pyruvate in the presence of oxygen (aerobic) or lactate when oxygen isn’t present (anaerobic). At the same time, gluconeogenesis synthesizes glucose from non-carbohydrate sources, often when the body is in a fasted state.

When glucose makes it into your bloodstream, it increases the level of blood sugar, which prompts the pancreas to release insulin. This hormone triggers glucose uptake into cells, from where it’s utilized as fuel by your muscles, stored as fat, or retained in the muscles or liver to provide energy later. As soon as glucose enters the cells, the pancreas gets a signal to stop producing insulin.

If your clients consume a moderate amount of carbohydrates, glycolysis should remain a smooth and efficient process in which the interplay between blood sugar and insulin levels is well regulated. However, if someone starts intaking too many simple sugars, blood glucose levels can consistently spike and crash or even remain chronically high, leading to hyperglycemia. If the athlete’s insulin sensitivity is low and insulin resistance is high, they can have trouble clearing excess glucose from their bloodstream, perpetuating the problem.

A study conducted at RMIT University in Australia found that “A single bout of exercise increases skeletal muscle glucose uptake” for up to 48 hours, while consistent training results in a persistent increase in insulin action in skeletal muscle.”[2]

Despite these short-term and long-term effects that your clients are probably benefiting from, some might still be consuming too many simple sugars. This could not only lead to fluctuations in blood glucose levels but also “increase the risk of metabolic disorders” and prompt “increased pro-inflammatory properties [and] decreased immune-regulatory functions,” according to a 2020 paper published in Nutrients.[3]

Keeping Blood Sugar Stable

To find practical solutions for any of your athletes struggling to find a balance between consuming enough carbs to power their performance and eating too much sugar, I reached out to Briana Butler, MCN, RDN, LD. She is a former WNBA player who is now the lead dietician and co-owner of Power Portions, which provides personalized sports nutrition and diet-free wellness services.

Butler said that when clients come to her who are overeating sugar, they often have been experiencing side effects. “If someone is taking in too many carbs or doing it at the wrong time, they can experience bloating, nausea, and even diarrhea,” she said. “We also see energy crashes from the ‘pickup and drop’ effect that an insulin spike can create if someone has a huge, carb-heavy meal before training.”

And while they might have been taught to frequently use refined carbs to maintain performance, some of your clients could be mismatching their sugar intake with the fueling requirements that their activity level requires.

“If you’re training or racing for an hour or less at a moderate pace – or even a higher one for a well-trained athlete – you probably don’t need anything more than water with a little salt in it,” Butler said. “You could also add in a carb rinse if you wanted to.”

That being said, certain sessions and race situations during which taking extra carbohydrates is appropriate and even necessary for your athletes.

“Once you go for much longer than an hour, like my marathon and ultra-marathon clients, you might need exogenous fuel to keep you going,” Butler said. “30 to 60 grams per hour is a simple guideline. That’s too much for most people in one sitting, so I usually suggest breaking it into 15-minute increments. For someone who has trouble taking in a lot of fluid during training, they could supplement their water consumption with a goo that contains just enough carbs and electrolytes.”

Another way for your athletes to become more strategic about their rate and total amount of sugar consumption is to dial in the type of supplements they use.

“There isn’t a one-size-fits-all approach for products containing simple carbs,” Butler said. “You could choose one based on fructose, glucose, a mix of the two or maltodextrin. It can be valuable to experiment a little before going all in on something that you’re not sure is going to work for you.”

Rethinking Snacking and Meals

Butler has frequently shared that when she was playing pro basketball in the WNBA and overseas, she came to realize that her nutrition began “on the plate and not in the pill.” In other words, she had to dial in her nutrition first and then consider supplementation tactics later.

This is still the advice she gives to coaches and athletes through the lens of timing not only the consumption of carbs but also other macros. At certain times of day, fat and protein can help slow the absorption of sugar to help reduce the chance of an energy spike that’s quickly followed by a crash.

“Solid, balanced meals earlier in the day could contain a mix of carbs, protein, and fat as long as you’re consuming them at least two to four hours before training or racing,” she said. “As you get closer to your activity and begin it, you can prioritize carbs. Then afterward, replenishing both glycogen stores and supporting the repair process with protein is key. A meal like chicken and rice with vegetables and fruit is a smart choice.”

When your athletes don’t have ready access to full meals, their snacking can also follow a plan. Rather than gorging themselves on sugary options, Butler recommends “smoothies with whey or plant protein, nut or seed butter sandwiches and trail mix” as good choices. These contain carbs and are also sources of longer-lasting fuel from fat and protein.

“You don’t have to supplement at all if you don’t want to,” she added. “Fruit like bananas, dates, and applesauce pouches are low-cost, portable options.”

To help your athletes find lasting success in curbing their sweet cravings and getting enough fuel without overdoing simple carbs, they need to find a consistent and holistic nutrition approach. If an athlete’s needs exceed your own coaching knowledge, consider referring them to a dietician or nutritionist.

“A professional can help provide expert guidance that’s tailored to the individual,” Butler said. “They can also help figure out the causes of any GI distress or other symptoms that might be related to diet or supplements.”

Using Fasting to Recalibrate the Liver and Pancreas

In our book, The 17 Hour Fast, my co-author Dr. Frank Merritt, an emergency room physician who is board certified in internal medicine, poses a rhetorical question to those athletes who’ve become reliant on topping off their glucose levels by frequently ingesting sugary supplements: “You spend so much time working on various elements of training to condition your muscles, connective tissues, heart, brain and so on. So why would you let your fuel system (i.e., your liver and pancreas) become so deconditioned, inefficient, and ineffective at producing ketones or sourcing glucose from anything other than simple sugars?”[4]

In other words, any of your athletes who are constantly activating their glycolysis pathway aren’t utilizing the alternatives of metabolizing glucose via gluconeogenesis or breaking down fat and certain amino acids into ketones through ketosis.

Merritt writes that another downside of continuous sugar hits during training and racing is that digesting the carbs could divert blood supply from muscles and vital organs, contribute to indigestion, diarrhea and dehydration, and send mixed signals to the autonomic nervous system. Plus, falling back on frequent glucose top-ups can create a psychological issue whereby some of your clients believe they cannot function properly otherwise.

The remedy? Ask your athletes to try tweaking their macronutrient intake in favor of more fat, moderate protein and fewer carbs. Most of the latter should be in the form of whole and sprouted grains, vegetables and fruit. Encourage them to cut down the frequency and overall quantity of their sugary supplements, and then suggest that they try fasting for 17 hours once a week.

“When you fast, you’re not just training your body to produce more ketones, which deliver longer-lasting energy that doesn’t wax or wane,” Merritt stated. “You’re also training your cells to utilize this more stable fuel source better. Plus, you’re making your body more efficient at producing glucose and putting it to work.”[5]


[1] Margarita Teran-Garcia et al., “Endurance Training-Induced Changes in Insulin Sensitivity and Gene Expression,” American Journal of Physiology–Endocrinology and Metabolism, June 2005, available online at https://pubmed.ncbi.nlm.nih.gov/15687108.

[2] J A Hawley and S J Lessard, “Exercise Training-Induced Improvements in Insulin Action,” Acta Physiologica, January 2008, available online at https://pubmed.ncbi.nlm.nih.gov/18171435.

[3] Reetta Satokari, “High Intake of Sugar and the Balance between Pro- and Anti-Inflammatory Gut Bacteria,” Nutrients, May 2020, available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7284805.

[4] Dr. Frank Merritt and Phil White, The 17 Hour Fast, 2018, 155-156.

[5] Merritt and White, The 17 Hour Fast, 157.

Coaching Guide Image Of Noah With A Client At A Table.

How to Be a Successful Endurance Coach

Learn from this guide to help you each step of the way as you build and grow your coaching business.

About Phil White
Phil White is an Emmy-nominated writer and the co-author of The 17 Hour Fast with Dr. Frank Merritt, Waterman 2.0 with Kelly Starrettand Unplugged with Andy Galpin and Brian Mackenzie. Learn more at www.philwhitebooks.com and follow Phil on Instagram @philwhitebooks.

Related Articles