The Keto Diet: Advisable for Hurdlers?
by Melinda Burris
In the past few years, the ketogenic or keto diet has become all the rage among those looking to lose excess weight quickly. Diets that promise quick results have always proven popular at least in the short term and are often referred to as the latest fad. The keto diet has shown itself to have staying power, however, and like diets that promise the possibility of shedding unwanted pounds rapidly, it has spawned a money-making machine, complete with the predictable supplements, how-to books, planners, recipes and apps.
The keto diet has come to the attention of fitness experts, trainers, and coaches because it has also become popular among endurance athletes as a substitute for the traditional high carbohydrate diet. This article will discuss what the keto diet is, its general pros and cons, and the debate over whether it is a viable nutritional plan for athletes participating in sports like hurdles that require strength training for muscle building to be able to deliver explosive power and high energy performances.
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What the Keto Diet Entails
The keto diet emphasizes eating a high intake of fat (55-60%)1, but it is important to note fat intake should be limited to certain types of fats — heart-healthy monounsaturated fatty acids (MUFAs). Examples include eggs, nuts, avocados, flax and chia seeds, and salmon. This diet focuses the majority of its caloric intake from these sources of fat while strictly limiting carbohydrates to only 5-10% of daily nutrients. Protein makes up the remaining 30-35% of the daily calorie allowance.
The goal of eating from these food groups in these specific percentages with an emphasis on very low carb intake is to reach nutritional ketosis to force the body from relying on carbs to fuel the brain and muscles and instead using ketones that are formed in the liver as MUFAs are broken down by the liver and used to create energy. This explains why so many Americans who spend so much time in front of computers or TVs or live otherwise sedentary lives are attracted to the keto diet as a means of losing unwanted fat with little effort.1
However, athletes also find ketosis appealing because as professional coaches Chris Carmichael and Jim Rutberg point out, they “have a virtually unlimited reserve of fat calories to pull from but can only store 1600-2000 calories worth of carbohydrate in muscles, blood, and the liver. An athlete fueled by ketones would be theoretically “bonk-proof”, since bonking is the result of running low on blood glucose.2 (Bonking refers to the sudden onset of fatigue experienced by endurance athletes caused by depletion of glycogen stores. It’s also commonly referred to as “hitting the wall”.)
The Keto “Flu” and Other Challenges
As noted, the keto diet is strict and can be difficult to maintain. You must not only severely restrict your intake of carbs, but you also have to watch your protein intake because eat too much and the body breaks this down into sugar which can keep you from reaching or maintaining nutritional ketosis. You also have to stay away from processed foods, so adhering to the keto diet requires planning and meal prep. Plus, like any diet, you are likely to crave the foods you are used to eating and can no longer have.
The keto diet is associated with a phenomenon that has been dubbed the “keto flu” which is characterized by short-term bouts of symptoms ranging from fatigue which can make it difficult to exercise, dizziness, nausea, vomiting, and constipation. Some people also experience difficulty sleeping and/or trouble concentrating. Susceptibility to and severity of “keto flu” vary and may last for as little as a few days or symptoms can linger for weeks depending on how long it takes your body to adjust. As with any diet, it is important to consult with your healthcare provider. Athletes should also consult with their coach or trainer before beginning a new regimen.
With the keto diet, it is very important to drink plenty of fluids and make sure you are getting enough salt and other electrolytes, as cutting out processed foods can mean your body is struggling to adapt to low blood sugar levels and low blood pressure. Staying hydrated and keeping your electrolytes in balance can alleviate the “keto flu”.
The Controversy
While there are those who see a distinct advantage in the ketosis approach and its use of ready fat stores for energy versus carbohydrate fueling that must be replenished more often, traditionalists assert that eliminating carbs in favor of fats ignores the effect fat fueling has on bodily function.2 Opinions are firmly entrenched on both sides, and not surprisingly, scientific studies have been ongoing for years in search of definitive answers to the questions raised.
A 2020 Scientific Study on the Keto Diet and Endurance Athletes’ Maximal Oxygen Consumption and Performance Outcomes
As previously stated, the traditional diet prescribed for endurance athletes has been one rich in carbohydrates to maintain a ready supply of glycogen stores which are necessary for energy. This requires athletes to eat every 1-3 hours while exercising. Aside from the inconvenience of constantly having to stop and refuel, the continual digestive process means that a substantial portion of the nutrients consumed do not go directly to the exercising muscles but are instead conveyed by the body “to the gut to aid digestion” with the added potential drawbacks of possibly causing a decrease in exercise economy while often leading to digestive upset, which in turn can “compromise the athlete’s ability to maximize training and competition outcomes.”3
Researchers point out that studies suggest that “training with low muscle glycogen availability promotes molecular changes that enhance training-derived endurance adaptations.”3 Investigations into ketogenic diets have also found that there is less lactate buildup, a condition caused by insufficient oxygen in the muscles to metabolize glycogen and glucose in the blood system. This suggests that a keto diet can increase recovery times for endurance athletes.3
The scientific study published in 2020 was a literature review of articles documenting research done through November 2019 and published in two online search sources, PubMed and Web of Science. Strict protocols had to be met for the inclusion of articles; each selection had to document endurance athlete’s ketogenic diet (EAKD), nutritional ketosis state had to have been achieved and documented by serum biomarker testing, and VO2 max output “and/or secondary outcomes” had to be recorded, and the publications had to be peer-reviewed and printed in English. All articles were required to be primary source materials and the hypotheses put forward had to have been tested using endurance athletes as study participants.3
Seven articles were found that documented VO2 max output/and/or secondary outcomes. The comparison of the effectiveness of a high-carb diet versus the EAKD proved inconclusive as findings were mixed. Researchers concluded there is a need for more randomized trials so that the effects of “EAKD consumption on endurance performance” can be better understood, specifically in light of the impact factors such as “genetics, recovery, sport type, and sex [may play] in moderating the influence of EAKD consumption on performance outcomes.”3 As is so often the case in scientific studies, as more questions are investigated, even more questions are raised.
Fitness Experts Weigh in on the Keto Diet and Endurance Performance
Coaches Chris Carmichael and Jim Rutberg point to scientific studies conducted by Dr. Louise M. Burke et al., in 2016 and 2020 to maintain that “the oxygen cost for exercise increases while exercising on a [low carb high fat] LCHF strategy. It takes approximately 8% more oxygen to liberate energy from fat compared to carbohydrate, which means relying primarily on fat reduces economy.”2 To put it bluntly, using fat as an energy source is not efficient for high endurance sports which is dependent on your Vo2 max or peak oxygen uptake.
Carmichael and Rutberg conclude (and many other fitness experts agree) that relying on a carb-centered diet that consists of regularly eating small meals every few hours to maintain your fuel supply is the best approach for endurance athletes looking to optimize both training and competition performance.2
Conclusion
No matter what diet you are on, it’s important to listen to your body. Eat natural foods whenever possible and moderation is key. As always, staying hydrated is always important, especially now as we are in the “Dog Days” of summer!
References:
- Booth, L. (2022). Should Strength Athletes Use the Keto Diet?
2. Carmichael, C. & Rutberg, J. Should Endurance Athletes Go Keto?
- Bailey, C.P. & Hennessy, E. A Review of the Ketogenic Diet for Endurance Athletes: Performance Enhancer or Placebo Effect?
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