Are you one of the many keto runners? Or, how do you become a keto runner? If you are curious, I hope to make a case for you that going keto is precisely what runners need to do to be fit, fast, and healthy.

The keto diet is becoming more popular. For good reasons, there are many health benefits. It is a strategy everyone is asking about. Ketosis is a process where your body learns to burn fat as its primary fuel source.

Ketogenic Diet foods
Keto diet for runners food

What is a Keto – Low Carb Diet?

Many runners can do this by going on a low-carb diet and consuming no more than 200 grams of carbohydrates daily. For some runners, this might mean a more restrictive diet, decreasing the carbohydrate intake to less than 10 grams daily.

This long-term process of your body burning fat as its primary energy source is called fat adaptation. Being fat-adapted offers everything an endurance athlete could dream of.

It provides endless energy from available fatty acids. This means sustained energy and no bonking. Keto diets are an efficient pathway to weight loss, mental clarity, and sustained energy levels.

What is a Keto for Runners and Endurance Athletes?

First, a refresher course on what a ketogenic diet is. It is a diet where your body burns fat and produces ketones. This requires you to lower your carbohydrate levels.

Many elite endurance runners can produce ketones with 200+ grams of carbohydrates daily. Others need to limit carbs to less than 5 grams per day.

Insulin and glucagon levels determine when the body makes ketones. It doesn’t matter what the number is; it matters that you find the level where your body is producing ketones.

Keto runners optimize performance with Periodized-Nutrition
Keto runners optimize performance with Periodized-Nutrition

Why do keto and running go hand in hand?

The fat-burning metabolic state is a handy process. The low-carb ketogenic diet allows athletes to access their fat stores. The leanest athlete has about 40,000 calories of fat on board as fuel.

This is about 20 times the energy stored in fat than in a carbohydrate. That means the keto diet for marathon runners works excellently to use your stored fat as fuel. 

Keto runners are happy runners.
Keto runners are happy runners

Why Go Keto?

Many endurance athletes can perform at a high level but are unhealthy. Dr’s Phil Maffetone and Paul Laursen highlight the issues with many endurance athletes in their article Athletes: Fit but Unhealthy?“.

Athletes become unhealthy because of their high carb intake. The best way to ensure you maintain your health as an athlete is to increase your fat burning.

Increasing your ketone levels is like buying health insurance.

You are ensuring you maintain your health while you make performance gains.

1) Normalize Blood Sugar

Not being able to tap into your fat stores results in hypoglycemia. The body’s ability to regulate energy depends on a regular supply of carbohydrates. If you don’t manage this well, you become hypoglycemic. 

The ill effects of hypoglycemia are clumsiness, trouble talking, confusion, loss of consciousness, and sometimes seizure. It is coupled with hunger, sweating, shakiness, and weakness. Wow, that doesn’t sound very pleasant.

Before I switched to the keto diet for runners, I had blood sugar problems. I would eat a meal and feel like I could slip into a coma afterward. You don’t want to go there if you have ever felt hypoglycemia. When you use the keto diet for runners, your body uses ketones for fuel; you will never have to worry about hypoglycemia again.

2) No More Disaster Pants

A second reason a ketogenic diet is beneficial for endurance runners is that it prevents gastric distress. An endurance runner can perform steadily for hours while consuming fewer calories than carbohydrate-dependent competitors.

As a result, a low-carb diet is a good solution for athletes who struggle with gastric distress. During exercise lasting 9-24+ hours, changes in blood volume, heat stress, and hydration status can slow or halt gut motility.

This is a problem when you are consuming large amounts of carbohydrates. The fluid and food stay in the gut too long to create gas, bloating, and nausea. GI problems are the leading cause of DNFs in ultra marathons. The prevention of gastric distress makes dietary ketosis a solution for ultra-distance athletes. 

3) Stay Strong

The third problem with excessive carbohydrates is high fasting glucose levels. This leads to decreased muscle mass.

The fancy term for this process is sarcopenia. Regular endurance exercise is insufficient to maintain muscle mass or function if you consume a high carbohydrate diet. Low-carb diets are protein and muscle-sparing. No one wants to be skinny and weak, especially as we age.

4) Avoid the dreaded bonk

Lastly, following a keto diet means runners won’t worry about bonking. Even very lean athletes have virtually an unlimited reserve of fat calories.

We can only store 1600-2000 calories of carbohydrates. We reserve carbohydrates in the form of glycogen. If an athlete train becomes dependent on glycogen and unable to use ketones for fuel, the athlete will bonk.

You have seen what happens when someone bonks…it isn’t pretty. Using fat as your primary fuel source makes an athlete “bonk-proof.”

Sian Welch & Wendy Ingraham demonstrates what bonking looks like.

5) Improve Performance

We discussed earlier why we want to be a fat burner. Having 40,000+ calories of fuel onboard during an endurance event is pretty handy.

Yet there are critiques of the ketogenic diet that say it is all well and good that you can go for miles and miles, but can you go fast?

Some athletes are concerned that they can only do high-intensity work by consuming significant amounts of carbohydrates.

The recent study Rethinking the role of fat oxidation: substrate utilization during high-intensity interval training in well-trained and recreationally trained runners study should put their fears to rest.

The study highlights the performance differences between high-performing and recreational athletes. The primary difference in performance is the rate of fat oxidation.

All athletes had similar perceived exertion (RPE) rates, blood lactate, and carbohydrate oxidation rates. The well-trained group had threefold higher rates of fat oxidation at high intensity.

The body’s ability to make and use ketones is a decided advantage for the health and performance of any athlete. Athletic performance improves when the body uses fat as its primary fuel source.

How to Adapt to a keto diet

By this point, you are at least curious and motivated to change your approach to sports nutrition.

Once adapted, you will likely never want to return to the traditional high-carb diet for endurance athletes. You may be asking yourself why wouldn’t anyone want to make the change.

Challenges in adapting to a low-carb, keto diet.

Here is the not-so-good news about a ketogenic diet. Changing your primary fuel source takes 4-12 weeks, as an athlete’s performance will suffer.

You will have a few days of the keto flu and feel like a semi-truck has hit you. The key to fat-adapted training is to have patience and moderate exercise. Lower-intensity heart rate training in your MAF Heart Rate zone; do not skimp on the electrolytes.

Why doesn’t everyone recommend keto?

Concerns about high-intensity exercise

Many coaches and sports scientists were taught carbohydrates are required for performance. They may have bought into the idea that a ketogenic diet is excellent for low-intensity events, but carbs are needed for high-intensity exercise.

But is that true? The confusion is that many scientists and coaches think we are not-burning fat when we hit our lactate threshold. The disorder is in the Indirect Calorimetry Substrate Estimates.

Testing Discrepancies

The problem isn’t that we stop oxidizing fat at high intensities; the problem is the testing equipment needs to learn how to read the fat once we hit the threshold. Higher lactic acid-induced production of CO2 [through HCO3- buffering].

This has a significant influence on the calculation of carbohydrate and fat oxidation. It creates an overestimation of the carb-burning. It also makes an underestimation of fat burning.

On the test, the estimation of fat use with these equations goes so low that it often becomes zero and then negative. Of course, you can’t have a negative for fat oxidation. Scientists typically misrepresent their data to say no fat is being burned. Rest assured, if you are keto-adapted, you can still oxidize fat at high intensities.

Concerns about Compliance

Once you spend a couple of months during the offseason adapting, your body learns how to burn fat as fuel.

Maintaining a high level of keto-adaptation is easy once you have made the change. Once adapted, you can add some carbohydrates during training and the training season.

The key is to keep glycogen stores empty. This is possible by doing fasted workouts. Warming up in a fasted state and reverting to a ketogenic diet after workouts.

This will ensure that your body will continue to produce ketones. During this period, your performance will continue to improve. Your health and quality of life with the increase and your power outputs will continue to rise.

Ketones are a clean-burning fuel that will generate less reactive oxygen species. Your recovery will be better.

Keto Runner Stephanie Before and After a Carnivore Diet
Stephanie Before and After a Carnivore Diet

Is it worth the effort?

The performance gains alone are worth the effort. There are other reasons that you might consider going keto.

Studies show that a ketogenic diet decreases triglycerides and manages Type II diabetes, lower fasting blood sugar, and more insufficient fasting insulin assists in cancer treatment and improves cognitive function.

These are the long-term benefits of going keto. The nice side effects of better performance are worth the adaptation period.

What about the Carbs?

Dietary ketosis does not require complete abstinence from carbohydrates. It is a matter of figuring out your limits. Training to deplete your glycogen stores will help ensure you are never “kicked out of ketosis.”

Cake is included

The way an athlete trains ensures their nutrition program is not sidelined by a slice of birthday cake, a beer at the ballgame, or a banana in an aid station. Learning how your body responds is how to maintain keto-adaptation’s health and performance benefits

Keto Runners - Questions and Answers
Keto Runners – Questions and Answers

Questions and Answers for Keto Runners

Can I run 3 miles per day on keto?

Absolutely. You may feel sluggish for a week or two as you adapt. Once adapted, you should feel amazing following a keto diet for runners.

What sports nutrition fuels can I eat as a keto runner?

This largely depends on your body and your goals.

Fat loss goal.

If your goal is fat loss, stick to low-carb fuels like exogenous ketones, Fat Bombs, and SFuels. UCAN and Hammer’s Perpetuem make great fuels for more prolonged efforts and higher-intensity training sessions.

Performance Goal.

During the Base Phase of training, use low-carb fuels like exogenous ketones, Fat Bombs, and SFuels. Add complex carbohydrates as needed during the Build Phase of training to improve performance. Include one or more low-intensity, fasted weekly workouts to maintain insulin sensitivity.

Performance Supplements

Amino acid peptides like Vespa Power help low-carb athletes tap into their fat stores. Electrolytes are essential in helping the body regulate fluids.

Can I run a marathon on keto?

Yes, you can run a full marathon on keto if you have taken the time to adapt to the diet.

Combining keto with strategic carbs is an excellent way to get your next personal record (PR) at your next race. Using complex carbs during a race will not kick you out of ketosis.

The carb allowance on keto depends on your goals. Ketoadaptation allows you to use carbs during training and racing. How many carbs depends on the individual athlete.

Exogenous ketones are another excellent choice for fuel during a marathon and with marathon training.

Can I run a 5k on keto?

Yes, you can run a 5k on keto. The decision to use strategic carbs depends on your race goals. If you are enjoying the race and not concerned about your time, leaving the fuel off during the race is okay.

Consider a long warm-up before the race starts if you are racing to get a PR. After the warm-up, adding strategic carbs and exogenous ketones will help boost energy during the race.

Is keto bad for my thyroid?

Because a keto diet is very satiating, many athletes undereat. Many athletes are satiated and need to eat more fat for fuel. This is a very high-fat diet. If you notice that you are not sleeping or recovering well, you will need to add more fat.

How much should a runner eat on a ketogenic diet?

I like this video from Nutrition with Judy about how much food to eat. She is discussing a carnivore way of eating. The information applies to keto athletes as well. As an athlete, ensure you get enough total calories to fuel your body to train hard and recover well.

Are keto snacks on a low-carb, keto diet?

Keto meals should be made of whole foods sources. Avoid heavily processed foods. If you crave sweets, add more fat, like high-fat fish, grass-fed beef, or olive oil. If that doesn’t do the trick, try a piece of dark chocolate.

Can I lose weight training on keto?

Yes! Being a keto-adapted athlete gives you the hunger control to feel good and lose weight. The keto adaptive body boost lets you have the best of both worlds: great performance and a great body.

Do I need a recovery meal after training sessions or races?

Different from carbohydrate dependant runners, refilling your glycogen stores is unnecessary.

What is a keto diet meal plan for runners?

A sample menu for keto runners:

Lettuce Wrap Bison Burger
Lettuce Wrap Bison Burger

Breakfast: Eggs cooked in butter with a side of bacon

Lunch: Garden salad with salmon dressed with olive oil and balsamic vinegar

Dinner: Bison burger wrapped in lettuce with a small side of sweet potatoes covered with butter.

In Conclusion

Low-carb running doesn’t have to be complicated. Once you get the hang of it, you will notice the benefits of faster recovery and improved endurance. Keto is the best-balanced diet for long life and longevity in the sport for most runners.

Need Help adjusting from regular diets to ketosis?

I am here to help; check out my coaching.

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