By Annie Bothma, September 2022
CARBS ARE STILL KING
Despite all the conflicting messages you may receive on social media about carbohydrates the science is still clear that carbs are key for maximizing endurance performance. You may hear or read about athletes who went "low-carb" and are still performing well or think if you consume less carbs you will "burn more fat" for fuel. If you look at what the best in the world are doing, dive into the research on carbohydrates or low-carb diets in athletes, you will quickly come to the conclusion that CARBS ARE STILL KING!
WHAT IS YOUR GOAL?
If your goal is to improve your personal best performance, even if you are not an elite athlete trying to get onto the podium, the amount of hours an athlete is spending to train preparing for an event does still require a lot of commitment, sacrifices and dedication. It just make sense to optimize performance to justify this time invested in preparing for a long endurance event like a marathon.
Carbohydrates have been proven to be the main fuel source during endurance exercise, especially when competing at a high-intensity and performance is the main goal. Diets high in fat have not been proven to be advantageous for athletes or show any enhancement in performance in endurance events.
WHY LOW CARB DIETS IS NOT THE BEST IDEA FOR PERFORMANCE
Adhering to a high-fat diet during training may enable you oxidize greater amounts of fat during training, but it will also negatively impact carbohydrate oxidation. This will impair an athlete’s ability to utilize carbohydrates on race day during high-intensity activities, since carbohydrates is the body’s primary fuel substrate when exercising at a VO2 Max of 70% or above. Studies suggest by following a low-carb diet for even as short as 5 days, down-regulated carbohydrate oxidation during training, even after a restoration of a 1-day high-carbohydrate intake before the event. Inability to cope, recover and adapt from the week-in-week-out training demands will impair performance in the months leading up to a big event and ultimately determine athletes level of performance on the race day or if they even make it to the start-line at all!
Long term adherence to a Low-Carb High-Fat (LCHF) diet may have even more negative health implications like:
RED-s is something that does not only affect females athletes, but also male athletes can suffer from detrimental performance and health consequences with being in a LEA-state. Low-carbohydrate intake put athletes at a greater risk for not meeting their energy requirements and potentially being in a LEA state.
Carbohydrates may also have a protective role on bone health and the immune system, which is important for athletes considering a bone stress injury or sickness will side-line them from training and competition.
LCHF diets often lack fiber, which may also have negative consequences on the digestive system.
Not training with carbohydrates while exercising will have negative performance consequences on race day, since it will impact your ability to fuel adequately during the race. You need to train your gut to tolerate the fuel you will be using during the event, and by following a LCHF diet and not consuming high-carbohydrate products or foods prior or during training, will cause GI upset on race day.
During training athletes may also experience poor recovery and increased mood disturbances, such as lethargy and irritability, when no carbohydrates are ingested, which could reduce your training adaptations.
HYPOGLYCEMIA
Carbohydrates not only serve as the muscle’s main fuel source during high-intensity training, but also the brain and may play a very important role in combating central fatigue during racing and prolonged or intense training sessions. Hypoglycemia is when blood glucose levels lower than 3 mmol/L when the glucose uptake by the brain is unable to meet the body’s metabolic requirements. Hypoglycemia is characterized by symptoms such as dizziness, cold sweat, nausea, reduced mental alertness and ability to concentrate, loss of motor skills, increased heart rate, excessive hunger, and disorientation. These symptoms show that low blood glucose levels with insufficient carbohydrate intake during prolonged exercise can have serious health and performance consequences.
WHY BE "FAT ADAPTED" IF YOU WILL HAVE AID STATIONS ON THE COURSE?
In an endurance event, like the marathon, where there will be aid stations frequently during the course of the event, it does not make sense to be "fat adapted." If you plan to consume carbohydrates during the event as your fuel source and if your event is not a self-supported event, there will be access to fueling available on the course. Alternatively, you can run with a few gels or chews in your pocket.
When competing in a self-supported event like a Marathon des Sables, consisting of six days of running over 250 kms (156 miles) across endless sand dunes, rocky jebels and white-hot salt plains, where athletes need to carry what they need to survive on their backs, it may make more sense to be more fat-adapted. In this case carrying less weight could be advantageous, but if fueling and hydration is available frequently on the course and knowing that consuming sufficient fueling and hydrating adequately is associated with increased performance the athletes needs to use the advantage in their favor.
SOCIAL IMPLICATIONS
Lastly, one needs to consider the social implications it may have on your personal life adhering to a low-carbohydrate diet. Following such a restrictive diet can cause unwanted stress, put strain on social relationships, and creates an unnecessary obsession with food in certain athletes leading to disordered eating patterns or a clinical eating disorder. This will lead to emotional and mental struggles which will definitely affect performance as well.
CARBOHYDRATES RECOMMENDATIONS FOR ENDURANCE ATHLETES
Hopefully you understand now why you need carbohydrates if you want to maximize your performance in the marathon. So let's get down to the nitty gritty on how much you need before and during your event.
CARBOHYDRATE INTAKE IN THE HOURS BEFORE EXERCISE
Athletes should have the last fairly large meal in the hours leading up before competition. Enhancing muscle glycogen pre-workout may enhanced endurance performance, but replenishing liver glycogen levels may be even more important when considering a pre-workout meal in the morning before a training session or race. Liver glycogen concentrations are substantially reduced after an overnight fast. Ingestion of carbohydrate tops-off the muscle glycogen stores, increases the liver glycogen reserves and contributes to the maintenance of blood glucose concentrations during the subsequent exercise bout. Stabilizing blood glucose will help mitigate any potential hypoglycemia that may occur if blood glucose levels drop too low.
The recommended meal consists of carbohydrate-rich sources that are low in fiber/residue, fat and protein and can be easily consumed and digested. The goal is to ensure that CHO targets are met, and to avoid any GI discomfort. Such a meal could include carbohydrate sources such as bread and jam or honey, cereal, porridge, bananas, canned fruit, and fruit juice.
The recommended amount pre-exercise:
1-4g of CHO/kg/BW in the 1-4 hours leading up to exercise.
FOR AN EXTRA BOOST ADD A BIT OF CAFFEINE
Caffeine could also be a useful way to enhance endurance performance and help reduce central fatigue. It is suggested that caffeine may increase glucose absorption and increase the delivery of carbohydrates to the muscles and resulting in higher exogenous carbohydrate rates. If you chooses to consume caffeine along with a carbohydrate rich meal prior to the training session this could be an added performance benefit.
CARBOHYDRATE INTAKE DURING EXERCISE
Convincing evidence from numerous studies indicates that carbohydrate feeding during exercise of about 60-minutes or longer can improve endurance capacity and performance. In fact, even exercise of shorter durations can be improved with rinsing a carbohydrate solution and spitting it out! Although this will not have any effect on the glycogen availability, since glucose is a key substrate for the brain, it may help reduce central nervous system fatigue. This shows ergogenic benefits of carbohydrate stretches beyond maximizing endurance performance through the mechanism of adequate muscle glycogen and blood glucose levels, since it has also been linked to the activation of brain centers involved in motor control. It may help reducing the rate of perceived exertion (RPE) an athlete is experiencing.
SPORT PRODUCTS VS REAL FOOD
Sports products such as gels, energy chews, sports bars and sports drinks are suitable choices and easy to carry on the running course. Consuming a standard 6% carbohydrate sports drink at aid stations located throughout an event will help to meet carbohydrate and fluid needs simultaneously. Sports products are also easily digested, low in fiber and protein and generally won’t cause as much GI discomfort compared to consuming foods with a mix of macronutrients and fiber. This is most likely the safest strategy if you have a history of GI discomfort/symptoms during training or racing.
Greater carbohydrate intake has been associated with improved performance. During prolonged exercise, the performance benefits of carbohydrate ingestion may be achieved by maintaining plasma glucose concentration and high rates of carbohydrate oxidation.If you are aiming to consume more than 60g of carbohydrates per hour it is best to use different types of carbohydrates, since limitations to exogenous carbohydrate oxidation appear to be in the absorptive process most likely because of a saturation of carbohydrate transporters. By using a combination of carbohydrates that use different intestinal transporters for absorption (multiple transportable carbohydrates), carbohydrate delivery and oxidation can be increased. Studies demonstrated up to 65% higher exogenous carbohydrate oxidation rates of multiple transportable carbohydrates, such as glucose:fructose combinations during exercise compared with a single carbohydrate source such as glucose only.
Recommended carbohydrate (CHO) intakes per hour to optimize performance:
Exercise lasting less than 1-hour: Mouth rinse or nothing.
Exercise lasting 1-2 hours: 30 - 60g of CHO/h
Exercise lasting greater than 2-2.5 hours: 60 - 90g of CHO/h
KEY TAKE AWAYS:
If your goal is to improve your personal best performance optimal carbohydrate intake before and during exercise is very important.
Carbohydrates are the main fuel source at high intensity exercise above 70% of VO2 Max.
Carbohydrates help with adequate training adaptations and lead to a better performance on race day.
Long term adherence to a Low-Carb High-Fat (LCHF) diet may have even more negative health implications such as LEA, GI disturbance, compromised bone health and immune system, illness or injury, poor recovery, and mood disturbances.
Low blood glucose levels (Hypoglycemia) due to insufficient carbohydrate intake during prolonged exercise can have serious health and performance consequences.
If you plan to consume carbohydrates during the event as your fuel source, if your event is not a self-supported event, there will be fueling opportunities on the course.
The recommended amount of carbohydrates in the 1-4 hours leading up to exercise is1-4g of CHO/kg/BW.
Caffeine may increase glucose absorption and increase the delivery of carbohydrates to the muscles and resulting in higher exogenous carbohydrate rates.
Convincing evidence from numerous studies indicates that carbohydrate feeding during exercise of about 60-minutes or longer can improve endurance capacity and performance.
Sports products such as gels, energy chews, sports bars and sports drinks are suitable choices and easy to carry on the running course.
Consuming a standard 6% carbohydrate sports drink at aid stations located throughout an event will help to meet carbohydrate and fluid needs simultaneously.
Sports products are easily digested, low in fiber and protein and generally won’t cause as much GI discomfort compared to consuming foods with a mix of macronutrients and fiber.
The recommended intake for carbohydrates during training is 30-60g for events lasting less than 2-hours and 60-90g for events lasting over 2-hours in duration.
Remember, your goal is just as meaningful for you and that is why it is worth it to fuel for the work required. Optimize your carbohydrates before and during your race so you can hit that goal you worked hard towards over the last few months!
** Stay tuned for a post on Carbohydrate loading protocols during race week and learn how super-compensating your glycogen stores in the last few days before race day can help you start and finish your race feeling strong! *
READ MORE:
Multiple transportable carbohydrates and their benefits (Jeukendrup, 2018)
Sport Nutrition, Third Edition. (2019) by Asker Jeukendrup, Micheal Gleeson