Low Carb Training And Running Research

Is a low-carb diet and running the optimum choice for both your body and your performance? This post examines the low-carb diet for competitive runners, its meaning, and how running on such a diet plan may alter performance.

Low Carb Diet

A diet with reduced carbohydrates generally means that you are consuming fewer carbs than what is typically recommended, which is typically 45-65% of your total daily intake. A running diet with a low carbohydrate intake could be anything lower than that.

The keto diet is an example of a diet that keeps carbohydrates to a minimum, with as little as 50g of carbohydrates per day. It would not be feasible to include pasta in a low-carb diet plan.

Carbohydrates are among the major components that provide our system with energy, alongside protein and fat. These three macronutrients are what provide us with the calories we need.

It’s widely accepted that carbs are the major energy source for the brain and muscles. A physically active person will require a greater amount of carbohydrates (fuel) than someone who is not very active.

Glycogen (saved starches) is the most vital and noteworthy fuel for direct to serious exercise, for example, long separation running.

Runner’s Low-Carb Diet

People usually adhere to a low carbohydrate regimen to shed some pounds. When someone begins a low-carb diet, there could be a brief decrease in weight that is because of alterations in the body’s fluid balance as carbohydrates do facilitate the body’s keeping fluid.

A low-carb diet can also be used to assist with certain health issues, such as diabetes or regulating blood sugar levels.

It may be tempting to attempt to lose weight by sticking to a low-carbohydrate diet and running, but how effective is this? Are runners who follow a low-carb diet really experiencing improved performance, or is it just a perception?

Research has been conducted extensively on sportspeople to gauge the impacts a low carbohydrate diet can have on their physical activities. It looks like low-carb ultra running may have a small advantage in that athletes don’t have to consume as many carbohydrates to make it through the race since their bodies can run off of fat for an extended length.

Vegan ultra runners and low-carb ultrarunners represent the two most disparate ways of training and competing.

However, that’s not to diminish the importance of carbohydrates. It’s always a balance. One’s personal choice, tolerance level, and overall dietary habits should be taken into account.

The ongoing studies indicate that carbohydrates are the ideal energy supply for ideal athletic proficiency, implying more successful PRs, extreme intensities, and quicker healing.

How Many Carbs Do Runners Need

Athletes who engage in endurance sports have been consuming carbs as a way to maximize their performance and energy level. An appropriate amount of carbohydrates should be consumed to guarantee the right amount of stored glycogen in the muscles and liver. Carbs and running go hand in hand.

Endurance athletes must consume 8-12 grams of carbohydrates per kilogram of body weight each day to get the most out of their glycogen supplies. The low-carb diet for runners does not meet the requirements that have been supported by research.

To get a clearer view of the situation, a 68.1 kg athlete with a body weight of 150 lbs would need between 545 and 817 grams of carbs per day. Here’s an idea for ways to get to those figures using snacks for carbohydrate loading.

Compare the keto diet to the previous discussion about eating less than 50g of carbs per day. Running a ketogenic diet, as well as running and intermittent fasting, are usually not suitable to maintain over an extended period, nor is it recommended for peak performance, improving the immune system, and injury prevention.

More on keto and running here. Carbohydrate recommendations for endurance athletes:

    • Daily: 8-12 g/kg/day
    • Pre-exercise: 10-12 g/kg/day + 1-4 g/kg (1-4 hrs. before the event)
    • During exercise: 60-70 g/hour or 90 g/hour if tolerate post-exercise
    • Post-exercise: 8-10 g/kg/day first 24 hr.

This is what we can consume before a lengthy run.

The quantity of glycogen kept in the muscles and liver affects one’s exercise performance directly. Research has revealed that a diet high in carbohydrates can greatly raise endurance levels and optimize training outcomes.

When the body’s muscle glycogen levels are not high, exhaustion will kick in quickly, the training will be less intense, and the results will not be as good. In addition, a diet low in carbohydrates may likely be lacking essential nutrients and vitamins.

Runners definitely need magnesium for many bodily operations, and it can be obtained in several high-carbohydrate foods. Eating enough food is always king. If you are looking for nourishment that will help you through ultra-running, this post has some great suggestions.

You can also use chewable snacks for running or ingestible gels to fulfil your carbohydrate requirements during extended efforts.

Carb Loading Strategies

Carbohydrate loading is a process exercisers who have endurance events coming up often utilize to raise the amount of muscle glycogen to greater than typical amounts. Runners who carb load can get more out of their workouts, allowing them to exercise for a longer period before feeling tired.

For activities that last more than 90 minutes or involve several matches close together, it is beneficial to consume a lot of carbohydrates. For activities that last over an hour and a half, it could be beneficial to consume an increased amount of carbohydrates in the one and a half to two days leading up to the event to improve performance by an estimated 2-3%.

An illustration of carbohydrate loading could involve eating a diet of moderate carbohydrates (5-7 g/kg body weight/day) for three days and then increasing the intake to a high carbohydrate level (8-10 g/kg body weight/day) for the remaining three days leading up to the race/event.

In addition, consuming carbohydrates during endurance activities also improves endurance performance. Events longer than 2.5 hours are associated with better performance when the carbohydrate intake is between 60-70 g/hour, and even up to 90 g/hour if it is tolerated.

Low-Carb Diet Considerations

Everybody’s energy needs and reactions to exercise will be unique. When considering if you should do low-carb marathon training, there are several things to consider, such as:

  • What is your goal?
  • Is your goal to finish the race, regardless of time?
  • To achieve peak performance and possibly acquire a PR?

Once your objectives are understood, this can assist you in determining which techniques to employ for instruction. Next, think about previous experience. Have you ever attempted a reduced carbohydrate eating regimen before? If so, how did you feel? Was it sustainable?

How was your energy level? Were you running or training at the time? If so, how were your performance times?

It is advisable to attempt a low-carb eating plan for running during non-peak training season if you haven’t tried it before. This is intended to give your body time to adjust and observe the sensations so that you can make the proper alterations in nutrition and exercise before starting your marathon training program.

Most runners who use low-carb diets don’t keep to them all the time; they will use them strategically. When they need to be at peak performance, they will start eating more carbohydrates before and during the race.

Marathoners need to consume more carbohydrates in the days before the race. Carbohydrate loading has been reliably demonstrated to give the body an abundance of glycogen to energize longer running periods.

When athletes were fed different diets composed of varying amounts of carbohydrates before they began exercising, those who had consumed a low-carb diet reached physical exhaustion sooner than those who had eaten a moderate-carb or high-carb diet. For example, in one study of athletes cycling until exhaustion:

  • High carb diet: 170 mins on bike
  • Moderate carb diet: 115 mins on bike
  • Low carb diet: 60 mins on bike

To put it simply, marathon runners should not use a low-carb diet for their training. Long-term testing has demonstrated the efficacy of high carbohydrate diets for endurance athletes, and they are frequently suggested.

The Train Low Hypothesis

The idea of a low-carb workout came to be when scientists noticed greater cell changes in response to small amounts of carbohydrates. At first, these findings were noted in experiments with people who had no prior experience.

Muscle glycogen being lowered stimulates cellular messengers to switch on proteins such as AMPK, thus producing changes in metabolism. This could lead to the generation of more mitochondria and better fat burning.

Researchers looked into the cellular-level changes in athletic people who had not been trained and thus started to investigate the effects of a low-carb diet on the performance of athletes who had undergone training in running and cycling.

One of the approaches utilized was exercising while having not eaten beforehand, two-a-day workouts with a restricted break in between that they are not allowed to consume carbohydrates, as well as attempting to acquire little rest.

One thing to note is that the carbohydrate-restricted research sessions did not typically extend to long runs, meaning training sessions that lasted two to three hours. Most laboratory-based studies employed endurance workouts with a duration varying between 60 and 120 minutes.

When examining various case studies, fasted training sessions were done at the start of marathon training and not during the specific preparation or taper phase (as seen in Stellingwerff’s 2012 case study in the International Journal of Sports Nutrition and Exercise Metabolism).

As the years went on and research was conducted, it was unclear whether or not the “train low” strategy was successful. In 2009, a research paper published in Acta Physiologica discovered alterations in muscle cells, yet no alterations in cardiorespiratory fitness.

An article published in Sports Medicine in 2018 came to the conclusion that, after reviewing eleven different studies, only 37% of the results pointed towards modest enhancement in performance. The investigators found that muscle changes do not necessarily result in improved exercise performance.

Current Consensus on Low Carb Availability in Training

An analysis published in 2021 in the Journal of the International Society of Sports Nutrition evaluated the outcomes of thirteen studies involving the occasional restriction of carbs.

The researchers determined that the current material of studies does not back the practice of running with low-carb sessions.

They declared that performing an acute bout of exercise with low amounts of carbohydrates does not appear to provide any advantage in terms of performance in endurance-trained athletes who have already adapted to this type of workout when compared to exercising with high carbohydrate availability.

Let it be noted: consuming carbs while exercising, instead of keeping away from them, actually aids in performance. Let us delve deeper into the fundamentals of the process and understand why sports nutrition is no longer relying on train-low methods.

It appears that research is being conducted to determine if there is a greater reliance on carbohydrates that would optimize the results of long-distance running. The rationale for performing glycogen depletion runs is often cited as the ability to increase fat burning.

Evidence from existing research indicates that increasing fat metabolism without increasing carbohydrate metabolism does not result in improved performance. Check out the International Journal of Sports Nutrition and Exercise Metabolism from standout experts in the area for a great article from this year.

When restricting carbohydrates, the burning of fat for energy usually leads to poorer running performance. Given that running economy is a factor in determining how well someone runs long distances, reducing carbohydrate intake will lead to increased fat oxidation, however, this is linked to a decrease in performance level or at minimal, no improvement.

What Runners Should Do Instead

Studies around nutrition/eating regimens have largely discouraged the use of strategies such as depletion of glycogen stores in favour of diets which better suit the amount of energy needed for performance. In this system, participants modify the number of carbohydrates they consume to the requirements of an exercise session.

Consuming carbohydrates before and throughout practice and competitions that require a lot of energy is adequate. Running requires more effort than biking due to its eccentric loading and weight-bearing nature which increases the amount of energy needed.

This model does not include extremely long runs that involve a deliberate decrease in glycogen reserves, as long-distance runs that last more than two hours require a large number of carbohydrates.

During any low-intensity activities, such as recovery outings, there will be a reduced need for carbohydrates. This is only if the athlete has high-energy availability.

Training with sufficient access to carbohydrates can enhance the quality of training, as well as carbohydrate metabolization and glycolysis that need oxygen.

In practical terms, having better training results in the ability to do more training and adjust effectively. Your body is better able to metabolize carbohydrates, allowing them to be easily taken in and put to use for the creation of energy.

The Risks of Carb-Restricted Training

Inadequate carb availability can impair bone turnover (Stellingwerff, 2019). There is an elevated danger of bone trauma due to the hindering of bone activity. It is self-evident that taking a break from training for six to eight weeks due to a bone stress injury will hurt performance.

A 2020 study in Nutrients discovered that if a person reduces their carbohydrate intake when exercising, it can disturb their body’s equilibrium of iron. One session alone will not produce much of a change in the amount of iron.

The researchers determined that following a low-carb diet promoted an uptick in hepcidin levels, thus hindering iron absorption over the long term. Athletes need iron for their well-being since it is the key ingredient in producing haemoglobin and myoglobin, which carry the oxygen they need.

This 2020 Nutrients review has detailed the negative effects of reduced energy availability for athletes. It is hard for a lot of casual sportspeople to work out their energy needs without help.

Running on low glycogen reserves and other methods of implementation that make it hard would create an even greater challenge.

Since a lot of female runners find it difficult to get enough carbohydrates, following the train-low routine can be risky. Men who run should be aware that prolonged insufficient amounts of carbohydrates in their diet could potentially lead to a decrease in their testosterone levels.

As advancement in the area of sports nutrition happens, scientists are joining the dots between RED-S and overtraining syndrome. A paper released in 2021 by Sports Medicine suggested that not eating enough may be a major cause of overtraining syndrome.

The pathways in both are alike, and they both have similar signs and symptoms. The scientists determined that even though 300-400 calorie losses do not appear consequential on their own when occurring often, they can accumulate and become medically pertinent.

This ongoing lack of energy and carbohydrates can prevent an athlete’s capacity to bounce back from and manage their training regimen. The main point: consuming adequate calories, specifically carbohydrates, and making sure you do not have a calorie shortage during the day is essential for continued athletic development.

I would posit that performing a glycogen depletion workout over and over again would be cause for alarm. This could involve developing certain abilities through practice or reducing one’s calorie intake.

Disordered eating can lead to amenorrhea, bad bone health, and dangerous eating disorders (which can be fatal). Athletes who show signs of having an eating disorder should not do glycogen depletion exercises.


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