The ketogenic diet has gained immense popularity in recent years, lauded for its ability to promote weight loss through carbohydrate restriction and increased fat intake. For runners considering a change in their eating habits, the question arises: is the keto diet suitable, and can it enhance running performance? To explore the potential pros and cons, we consulted with dietitians to provide a comprehensive understanding of the keto diet for runners.
Understanding the Keto Diet
The ketogenic diet (or keto diet) imposes strict guidelines on macronutrient intake, emphasizing a high-fat, moderate-protein, and very low-carbohydrate ratio. Typically, individuals following a keto diet derive 80% of their calories from fat, 15% from protein, and a mere 5% from carbohydrates. This drastic reduction in carbohydrate intake forces the body to seek alternative fuel sources.
Staple foods in a keto diet include fish, meat, eggs, dairy products, oils, and green vegetables. Even complex carbohydrates, such as whole-wheat pasta, rice, potatoes, and fruit, are restricted.
How the Keto Diet Works
When carbohydrate availability is limited, either through dietary restriction or prolonged fasting, the body enters a metabolic state called ketosis. In ketosis, the body turns to fat as its primary fuel source, breaking down fatty acids to produce ketones. These ketones then serve as an alternative fuel for the brain and body.
It's important to distinguish the ketogenic diet from a general low-carb, high-fat diet. The keto diet specifically aims to elevate ketone levels in the blood, inducing and maintaining ketosis.
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Potential Benefits of the Keto Diet for Runners
While carbohydrates are the body's preferred fuel source, ketones can also effectively fuel the brain and body. According to Lizzie Kasparek, R.D., a sports dietitian with the Sanford Sports Science Institute, being in ketosis does not necessarily lead to reduced muscle glycogen levels. Kenneth Ford, Ph.D., director and CEO of the Institute for Human and Machine Cognition, suggests that keto-adapted athletes may improve their ability to burn fat for fuel while still maintaining glycogen availability, especially with strategic carbohydrate loading.
The suitability of a keto diet for runners depends on individual goals, and the scientific consensus on its performance-enhancing effects remains inconclusive. Many studies on keto and athletes involve small participant groups, highlighting the need for further research.
One small study published in the Journal of the International Society of Sports Nutrition found that a 10-week keto diet improved body composition and well-being in endurance athletes but did not enhance their performance. Initially, the athletes experienced reduced energy levels and difficulty with high-intensity exercise. Another small study in Medicine & Science in Sports & Exercise reported a decline in running speed and power in trained athletes following a keto diet, with running speed at VO2max decreasing by 5 percent. A review of seven articles on the subject also indicated limited evidence supporting the benefits of keto for endurance athletes, with mixed results regarding VO2 max and other performance outcomes.
Potential Downsides of the Keto Diet for Runners
Kasparek notes that there's limited research demonstrating improved performance among runners on a keto diet. Ford emphasizes that studies with negative results often involve athletes who are not sufficiently fat-adapted or even in ketosis, making it difficult to accurately assess the diet's effectiveness.
High-intensity exercise, crucial for many runners, primarily relies on carbohydrates as fuel. Runners participating in long-distance events like ultramarathons may benefit from fat adaptation, as their bodies increasingly rely on fat for energy production in the later stages of the race. However, for most runners, carbohydrates remain the preferred fuel source, particularly at higher intensities.
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Kasparek explains that while the body can burn fat as fuel at lower intensities, runners may sacrifice key workouts or race performance by restricting carbohydrates, the primary fuel source for high-intensity activities.
Considerations Before Trying the Keto Diet
Whether the keto diet is right for you depends on your individual needs and goals. Runners seeking to improve their ability to tap into fat stores during long, low-intensity training sessions may benefit from reducing carbohydrate intake and increasing fat consumption. However, achieving ketosis is not a prerequisite for this approach, known as "carbohydrate periodization."
Runners who engage in speed workouts, shorter distances at faster paces, or high-intensity training are generally better off consuming a healthy, balanced diet that includes carbohydrates.
For weight loss, Kasparek suggests that adjustments to a regular diet, such as increasing healthy fat intake or eliminating processed foods, can be effective. A calorie deficit remains a key factor in weight loss, and a single banana is unlikely to derail progress.
Keto and Carnivore Diets: An Alternative Perspective
For runners already following a low-carb, keto, or carnivore diet, there may be no need to drastically increase carbohydrate intake for race training. While glucose provides a quick energy source favored by elite endurance athletes, recreational runners and those prioritizing long-term health may find that a ketogenic or carnivore diet effectively fuels runs, supports faster recovery, and aligns with broader wellness goals. Elite athletic performance often comes at the expense of long-term health.
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Carbohydrate loading, a common practice among marathoners and ultra-runners seeking to maximize glycogen stores, may not be necessary for recreational runners. Overemphasizing carbohydrates can lead to reduced protein intake, which is essential for muscle repair and recovery. Insufficient protein intake (approximately 2-3g per kilogram of body weight daily) can leave muscles undernourished, resulting in prolonged soreness, increased inflammation, and slower recovery.
Diets that prioritize carbohydrates while neglecting dietary fat can disrupt hormonal balance, which is vital for energy, recovery, and overall well-being. Essential fatty acids are necessary for the production of hormones like cortisol, testosterone, and estrogen. High-carb diets, especially those rich in refined carbohydrates, can cause significant fluctuations in blood sugar levels, leading to fatigue, irritability, and inconsistent energy levels during training or races. Excessive carbohydrate intake, particularly from sugary or refined sources, can also promote systemic inflammation, hindering recovery and increasing the risk of overuse injuries.
A ketogenic diet (low carb, moderate protein, high fat) and a carnivore diet (animal-based, typically ketogenic) rely on fat as the primary fuel source. By becoming fat-adapted, the body can efficiently burn fat for fuel, providing a steady energy source.
Adapting to Keto or Carnivore Diets as a Runner
Adapting to a low-carb diet as a runner requires careful planning. Low-carb diets can increase sodium and potassium losses, necessitating supplementation with natural electrolytes to prevent fatigue and cramps during training and races.
To support muscle repair and recovery, aim for approximately 1.6-2.2 grams of protein per kilogram of body weight daily. It can take 4-6 weeks for the body to become fully fat-adapted.
Fueling Strategies for Keto Runners
Some runners perform better with small pre-run meals, while others prefer running fasted.
Pre-Run (Optional)
A Chief Collagen Bar can provide a quick and clean source of protein and fat, while also increasing tendon strength. Alternatively, the collagen bar can be crumbled into full-cream yogurt or cottage cheese.
During the Race
Chief Beef Bars or Collagen Bars offer easily digestible fuel sources for long races.
Post-Race Recovery
A hearty meal with fatty meat and collagen-rich bone broth, supplemented with Chief Collagen Powder, can aid recovery. For those who find it difficult to eat immediately after running, a smoothie made with frozen bone broth cubes, kefir, and Chief Chocolate Collagen Protein powder can be a gut-healing and soothing option.
Addressing Concerns About Reduced Performance
Some runners worry about reduced performance on a low-carb diet. While ketogenic and carnivore diets limit carbs, they donât deplete glycogen entirely. Eating a variety of animal-based foods, including organ meats like liver, provides a rich source of vitamins and minerals.
Running performance doesnât have to rely on carbohydrate loading, especially for recreational athletes. By focusing on fat and protein as primary energy sources, you can achieve steady energy, faster recovery, and improved overall health.
Scientific Evidence and Research
The ketogenic diet has garnered attention as a potential ergogenic aid for endurance athletes, aiming to minimize reliance on carbohydrates. While athletes are typically advised to consume adequate carbohydrates, some propose that the limitations of carbohydrate storage may hinder athletes competing over extended periods.
Carbohydrates are stored in the body primarily as glycogen in muscle tissue (300 g) and liver tissue (90 g), along with glucose in the bloodstream (30 g), totaling approximately 1680 kcal of available energy. This necessitates frequent glycogen replenishment during prolonged activity, redirecting nutrients from exercising muscles to the gut, potentially reducing exercise economy and causing digestive disturbances.
Research suggests that training with low muscle glycogen availability can promote molecular changes that enhance endurance adaptations. Ketogenic diets have also been shown to reduce lactate accumulation after exercise, contributing to enhanced recovery.
In contrast to the limited carbohydrate storage, the body can store vast amounts of energy as fat. One pound of fat yields approximately 3500 kcal, making fat a substantial energy source, even for lean endurance athletes. Theoretically, athletes who tolerate a ketogenic diet could sustain longer training periods with consistent energy levels and reduced need for refueling, maximizing the aerobic benefits of training and competition. Some evidence suggests that highly trained individuals may experience a steady supply of energy for the body and brain during prolonged exercise and accelerated recovery time post-exercise.
However, it's important to note that studies examining the effects of EAKD on VO2 max have yielded mixed results. Some studies have reported significant increases in VO2 max across all diets, while others have found no significant changes. Similarly, secondary outcomes such as Time to Exhaustion (TTE), Race Time, Rating of Perceived Exertion (RPE), and Peak Power have shown limited and heterogeneous findings, making it difficult to draw definitive conclusions about the efficacy of EAKD for performance benefits.
A Keto Meal Plan for Runners
A keto meal plan for runners combines the energy needs of running with the low-carb, high-fat keto diet. It includes nutrient-dense foods that provide sustained energy and aid in recovery. This plan is tailored for runners who want to leverage the benefits of ketosis for endurance and performance, fueling long-distance runs with ketones instead of carbs.
Foods to Eat
- Fatty Fish: Salmon, mackerel, and sardines for omega-3 fatty acids.
- Lean Proteins: Chicken, turkey, eggs, and lean cuts of beef for muscle repair.
- Low-Carb Vegetables: Spinach, kale, broccoli, and asparagus for vitamins and minerals.
- Avocado: A rich source of healthy fats for sustained energy.
- Nuts and Seeds: Almonds, walnuts, chia seeds, and pumpkin seeds for portable snacks.
- Berries: Limited quantities of strawberries, blueberries, and raspberries for antioxidants.
- Full-Fat Dairy: Greek yogurt and cheese for added protein and fats.
- Healthy Fats: Olive oil, coconut oil, and avocado for energy.
- Protein Shakes: Keto-friendly protein shakes for post-run recovery.
Foods to Avoid
- High-Carb Sports Drinks: Choose water or electrolyte-rich options without added sugars.
- High-Sugar Energy Bars: Opt for low-carb, high-protein bars or homemade alternatives.
- Processed Meats with Fillers: Choose fresh, unprocessed meats for protein intake.
- Sugary Snacks: Avoid candies, sweets, and high-sugar treats for energy.
- High-Carb Pasta: Substitute with low-carb alternatives like zucchini noodles or shirataki noodles.
- Highly Processed Oils: Choose natural fats for cooking.
- Starchy Vegetables: Be mindful of carb-rich vegetables and adjust intake based on activity level.