Throughout history, endurance athletes have commonly ingested significant quantities of carbohydrates to effectively power their training sessions and enhance their performance during races. This approach appears logical considering the advantageous effects that carbohydrates provide.
Carbohydrates are necessary to fuel high intensity activity, which means that a high-carbohydrate diet is important for some of the fastest runners in the world. Therefore, it can be concluded that where high-intensity activity is required, carbohydrates are necessary, and the fact that some of the fastest runners have a very high carbohydrate diet does not necessarily argue for it.
The Case for Some Lower Carbohydrate Meals
Recent studies have shown that endurance athletes can reap advantages not only from high carbohydrate intake but also from periods of reduced carbohydrate consumption. Specifically, intentionally limiting the athlete’s carbohydrate availability for certain durations, whether it be during the season, month, week, or even day, can induce adaptations that may enhance performance.
It seems that the increase in performance is a result of the athlete’s improved capacity to burn fat (and produce ATP) during higher workload, allowing for the preservation of muscle glycogen for more vigorous activities/sprints, and postpones the start of fatigue.
In summary, training in a conscious state of reduced or minimal carbohydrate intake, even if it leads to a decrease in the intensity of the training session, can still lead to developments that enhance long-term performance.
Why Not Just Go High Fat
It is not necessary to have excessive or consistently high fat intake, much like always having a high intake of carbohydrates does not seem necessary.
Despite the potential to enhance the utilization of fat for a certain amount of energy requirements, fat metabolism still has several restrictions that hinder its ability to sustain high-intensity activities. Moreover, following a high-fat and low-carbohydrate diet may negatively affect carbohydrate oxidation, resulting in a possible decline in performance during maximum exertion.
In a study conducted by Morton et al. in 2009, it was shown that when a second training session was started with limited carbohydrate availability, there was an upsurge in the molecular mechanisms that enhance oxidative/fat metabolism.
Despite these enzymatic adaptations, there was no increase in performance compared to when carbohydrates were accessible. Nevertheless, this discovery implies that altering the pre and post-workout nutrition, in conjunction with the training regimen, can influence the specific adaptations the body undergoes.
One possible analogy that is both suitable and simplistic could be the comparison to a hybrid motor vehicle, which operates on a combination of petrol (gas) and electricity.
Rather than solely prioritizing one type of ‘fuel’ over the other, it would be wise for athletes to acquire proficiency in utilizing both. Developing the capacity to effectively utilize both fat and carbohydrate as energy sources would be highly beneficial for endurance athletes to improve their performance.
How Might You do This
One method that may prevent a decline in carbohydrate oxidation and boost fat metabolism is exercising in a fasted state. In order to achieve this, begin a morning training session without consuming carbohydrates (i.e., without eating breakfast or having carb-containing drinks before or during the session).
There is no evidence suggesting that consuming protein would reduce the adaptive responses to carbohydrate restriction. Therefore, it would be appropriate to have nothing or opt for products such as whey protein before or during morning training.
If you don’t like the idea of exercising on an empty stomach, another way to achieve similar results is by limiting carbohydrate intake between sessions on the same day. Choose meals containing higher amounts of fat, protein, and vegetables for the time between sessions one and two.
Possible rephrasing: Possible meal options you can find here are salmon with eggs, Greek yogurt alongside whey protein, and red meat paired with vegetables. It is possible that you may perceive the intensity of the second session to be lower than anticipated, particularly when compared to one conducted while in a state of high carbohydrate intake.
Although the reduced intensity may lower training performance, the positive effect on metabolic pathways could counterbalance it, leading to improved capability in utilizing fat for energy and potentially enhancing long-term performance, rather than negatively impacting it.
When sessions require more intensity, it is often recommended to have higher carbohydrate intakes (although this is not always the case). Maybe, on one or two occasions per week, a morning session could be done in a fasted state, while once a week it might be possible to recover with limited carbohydrate availability between two sessions.
In order to prepare for optimal performance, it would be wise to engage in preparation and training that encompasses a range of conditions and scenarios. The composition of an individual’s nutrition should align and support the frequency, intensity, and duration of their training sessions, as well as their athletic ability and the current season they are in.
What Happens when Carbs are Restricted
When we severely limit our dietary carbohydrates, the body enters ketosis, which is a metabolic response. In ketosis, the body switches from using glucose as its primary fuel source to burning body fat and using ketones for fuel. This metabolic switch has various known benefits for the body, including fat loss and improved brain function. The way a ketogenic diet fuels the body differs greatly from a diet high in carbohydrates. When you consume a meal rich in carbohydrates, the carbs are broken down into glucose, which is then transported into cells by insulin for energy production.
When a high-carbohydrate diet is followed, the body depends on glucose as its primary fuel source and rarely utilizes fat reserves for energy.
The body is forced to rely on fats for fuel when following a ketogenic diet, contrary to the usual reliance on carbohydrates. This transition from using carbs as the primary source of energy to using fats is referred to as ‘fat adaptation’ and may take several weeks or months to fully complete.
Endurance athletes can incorporate low-carb diets into their routine.
A low-carb, high-fat diet is popular among endurance athletes mainly because it allows them to avoid using their limited carbohydrate stores. Instead, this type of diet makes use of the ample fat reserves that even lean athletes have, which can provide fuel during extended training sessions.
Research indicates that athletes who have received proper training and adhere to an LCHF diet exhibit increased rates of fat oxidation and rely on a greater proportion of fat as an energy source. Consequently, this could enable athletes to sustain longer physical activity without experiencing the typical states of extreme fatigue caused by depletion of carbohydrate reserves, commonly referred to as ‘bonking’ or ‘hitting the wall’.
Athletes who follow a high-carbohydrate diet rely on a steady intake of carbohydrates to keep their fuel tank topped up during training. This approach is different from the one mentioned earlier.
Does a Low-Carbohydrate Diet Lead to Improved Performance
Although numerous studies indicate that a low-carbohydrate diet enhances fat oxidation, the evidence supporting its impact on performance is limited. Fat metabolism is slower than carbohydrate metabolism, therefore making it the preferred fuel option during low-intensity exercise (peak fat metabolism typically occurs at around 45 to 65 per cent of VO2 max).
Fat utilization is highest during lower intensity exercises like cycling, walking, running, or swimming. However, as the training speed or pace increases, our reliance on carbohydrate metabolism also increases.
If your muscles’ glycolytic capacity, which is fueled by glucose derived from the carbohydrates we consume, is limited, it can adversely affect your performance during explosive movements such as sprints.
Although an LCHF diet can effectively sustain your endurance training, it is not guaranteed to enhance your running speed. In truth, endurance athletes, especially when competing, require metabolic flexibility, which enables them to efficiently utilize both fats and carbohydrates for energy during exercise.
The Cyclical Approach
Not everyone may find a very low-carbohydrate or ketogenic diet suitable or beneficial. This is particularly the case for individuals with kidney or gallbladder disease, specific thyroid conditions, or those who are hyper-responsive to cholesterol or undergoing high levels of stress.
If not well planned, adhering to the diet can be difficult for others and may result in a deficiency of valuable nutrients and electrolytes.
One alternative for endurance athletes to consider is the adoption of a cyclic ketogenic diet as a more sustainable approach. This approach usually entails carb-loading for one to two days during the week when engaging in high-intensity training, and then following a low-carbohydrate ketogenic diet for the remaining days. By doing so, the body can enter ketosis and sustain energy levels during lengthy training sessions without sacrificing performance.
