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Keto And Endurance Athletes

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When coaching a group of athletes, it is common to get too focused on modifying the specifics of their training schedules, overlooking their overall preparation, lifestyle, and performance.

In spite of having the best program globally, an athlete will face difficulties in achieving their maximum potential unless assistance is provided in fine-tuning other essential aspects of their approach. In the upcoming months, we will focus on improving sleep, hydration, and other vital areas. However, let’s begin with nutrition and specifically explore whether the ketogenic diet could be beneficial for your clients.

Ketogenic Diet

In order to determine whether your athletes would thrive or struggle if they switched to a keto diet, we must initially provide a brief overview of what the diet consists of.

The ketogenic diet is essentially a way of eating that involves a high fat intake, moderate protein consumption, and low carbohydrate intake. The origins of this diet can be traced back to the early 1900s when researchers observed that fasting often led to a reduction in seizures among individuals with epilepsy.

In his book Wired to Eat, Robb Wolf discusses the creation of a diet that imitates fasting. This involves significantly decreasing carbohydrate intake, increasing fat consumption, and maintaining moderate levels of protein. By doing so, individuals can achieve a prolonged state of “nutritional ketosis” for long-term adherence.

What is the meaning of nutritional ketosis, you may ask? In simple terms, it refers to the situation where your body mainly uses ketones for energy through a process known as ketosis, rather than relying on glucose derived from gluconeogenesis.

To maintain ketosis, your athletes should limit their overall daily carbohydrate intake to less than 30 grams, excluding any simple sugars. Additionally, they should be cautious of consuming excessive protein amounts as certain amino acids can be utilized for gluconeogenesis, while emphasizing the consumption of fats.

When considering macronutrient percentages, a ketogenic diet consists of roughly 5 to 10 percent carbohydrates, 30 to 35 percent protein, and 55 to 60 percent fat.

Supporters argue that the keto diet offers a steady supply of energy by minimizing fluctuations in blood sugar levels, aids in building muscle while reducing excess body fat, and improves cognitive abilities. Additional benefits may encompass decreased inflammation, lower likelihood of certain chronic ailments, and improved sleep.

Does the Ketogenic Diet Help Endurance Athletes

This is the point where the situation becomes complicated since, in recent years, researchers trying to address this question have generated contradictory findings. Let’s begin by examining some studies that support the keto diet.

A group of exercise scientists at Waterford Institute of Technology in Ireland partitioned 20 male athletes specialized in endurance into two sets. The initial group adhered to a diet high in fat but low in carbohydrates, while the second group followed the opposite. At the end of a 12-week period, both groups underwent a 100-kilometer time trial, a six-second sprint, and a critical power test.

The performance of both groups was the same during the long time trial. However, the keto-mimicking group showed better fat utilization for energy, enhanced their body composition, and potentially due to lower body fat percentage, increased their peak sprinting power relative to their body weight.

The European Journal of Sport Science published a review that revisited the argument commonly raised by critics of the keto diet. The review disputes the claim that athletes may struggle to sustain their performance and surpass a certain point of glycogen depletion unless they consume carbohydrates before and during their workouts.

The authors proposed that the occurrence of ‘bonking’ might be due to an athlete’s inability to effectively use their body fat. They suggested that the best way to enhance the body’s fat oxidation ability is to decrease carbohydrate consumption to a level that triggers nutritional ketosis (ketone levels >0.5 mmol/L) and increase fat intake for a few weeks.

However, previous studies have indicated that although the ketogenic diet does provide certain health benefits, it does not enhance performance.

A higher-carb diet was found to have more evidence supporting its effectiveness in improving endurance performance in elite athletes, according to a review published in The Journal of Physiology. The review also mentioned that there was only anecdotal evidence connecting increased fat utilization to endurance performance in elite athletes.

A study conducted on endurance athletes in New Zealand discovered that transitioning to a high-fat, low-carbohydrate diet brought about improvements in specific skin conditions, decreased inflammation, and enhanced recovery according to self-reported evaluations. However, it also posed challenges for them in completing high-intensity training sessions and resulted in decreased energy levels during training.

How do diets like Keto impact exercise

Does this imply that LCHF diets are the solution for our endurance-focused athletes? Not quite – there is no universal answer as an athlete’s diet is affected by several factors.

This article aims to analyze best practices for an endurance athlete by taking an evidence-based approach and considering factors such as the sport performed, training frequency, personal food preference, food allergies and intolerances, and whether the athlete is on or off season in their training cycle.

Type of exercise determines which fuel our bodies use

In low intensity exercise, the main fuel sources are a combination of carbohydrate and fat, with fat being the primary source.

Said to use carbohydrates as the primary source of fuel, high intensity exercise is not suitable for low carbohydrate diets. There is a belief that low carbohydrate, high fat diets such as Keto may be beneficial for low intensity exercise; however, current research does not support this notion.

The body utilizes different fuel sources, such as carbohydrates or fats, during exercise. The fuel type utilized is determined by the duration and intensity of the session. For low intensity sessions (like a relaxed 30-60-minute walk or jog), the body primarily relies on aerobic processes and uses a combination of carbohydrates and fats.

When engaged in more intense activities that require difficult breathing, such as shuttle runs or hill sprints, the body will predominantly rely on carbohydrates as its primary fuel source. This occurs especially when the athlete is operating at or near their maximum capacity.

The athlete’s ability to use fuel during moderate intensity exercise is specific to each individual and is influenced by their aerobic training adaptations over time. This is due to the improvement in fat oxidation, resulting from training, which allows athletes to depend less on carbohydrates during moderate intensity exercise sessions, such as team field sports.

Low carbohydrate diets are not ideal for high intensity exercise, but could they work for endurance exercise

Based on current research by Burke, 2015 and Burke et al., 2017, it is indicated that the intake of LCHF diet might have a notable detrimental impact on performance output as the intensity of the activity rises, specifically during activities such as sprinting or hard, short bursts.

On the other hand, endurance athletes may find that LCHF diets can decrease their fatigue response when exercising at a low intensity. This implies that these athletes may be able to maintain a suboptimal pace for a longer period, suggesting a possible advantage for their endurance performance.

Determining a diet that will enhance performance is necessary for any athlete seeking to achieve optimal results, as simply “going” is not the objective.

Burke et al. (2017) carried out a four-week investigation on elite race walkers to examine the impact of a ketogenic low carbohydrate, high fat (LCHF) diet compared to a high carbohydrate (CHO) low fat (HCLF) diet. The study specifically concentrated on fuel adaptation, metabolism, and performance during a period of three weeks of intense training.

There existed three groups that followed different diets.

  1. A high carbohydrate diet (HCLF)- 60-65% of energy came from carbohydrates, 15-20% protein, 20% fat; consumed daily and before during and after training (9 women).
  2. Periodized CHO group: Same composition as HCLF, at different intervals according to training demands and fuel needs with some training sessions focused on high CHO availability (high muscle glycogen, CHO feeding during session) and others with low CHO availability (low pre-exercise glycogen, overnight fasted or delayed post-session refueling) (10 women).
  3. A LCHF diet: 75-80% fat, 15-20% protein, <50g/day CHO (10 women).

Group 3, who consumed the low carbohydrate diet, did not experience any benefits to their performance, according to the research findings.

Despite undergoing 3 weeks of intensified training, the LCHF group did not show any improvement in performance levels. In contrast, the athletes assigned to other dietary patterns all exhibited significant performance improvements after the same 3 weeks of intensified training.

Furthermore, it was discovered that athletes fueled on a low-carbohydrate, high-fat (LCHF) diet require a greater amount of oxygen to complete the same level of physical exertion.

The carbohydrate groups (diets 1 and 2) achieved an improvement in performance, which is interesting. Previous research conducted by Burke et al. (2015) also observed a decrease in cycling and sprinting performance when athletes followed a LCHF diet.

The study conducted by Lambert et al. (1994) provided evidence that a LCHF diet could be beneficial for endurance athletes. Over a two-week period, five elite cyclists with endurance training were instructed to consume either a HCLF diet (consisting of 74% carbohydrates and 12% fat) or a LCHF diet (consisting of 67% fat and 7% carbohydrates) in a random sequence.

During the training session, they were instructed to exercise until exhaustion at 60% of their VO2max, which is their maximum aerobic exercise capacity. The participants who followed the LCHF diet increased their time to exhaustion during moderate intensity exercise (60% of their VO2 max), which was longer than the HCLF diet.

The studies support the idea that athletes may be able to sustain longer duration on the LCHF dietary protocol, but only at lower intensities.

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