Is The Keto Diet Good For Bodybuilding – The pros and cons

Written by Tihomir Stefanov, M.S.(C), PT

| Published on

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Is it good to use the keto diet for bodybuilding ?

The ketogenic diet has been getting more and more popular among the fitness masses and often times, people claim that it works like magic.

The premise is that with keto, you will be conditioning the body to use ketones as the main source of energy for mental and physical activities.

Ketones are essentially an alternative fuel source, which are synthesized by the liver during fat metabolism.

If you’ve followed our articles thus far, you should know that the body mainly uses carbohydrates and fats as sources of fuel.

Nevertheless, if those two are unavailable, the body can use proteins as the last resort source of fuel.

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And so, during their metabolism, carbohydrates and fats turn into their respective end products – Glucose (carbs), fatty acids (fats).

Protein of course, turns into amino acids which then get used by the body to sustain an array of vital functions, growth and recovery.

What is the ketogenic diet?

what is the ketogenic diet

Alright, as we just learned, due to the fact the body is an adaptive machine, which can get exposed to a number of factors, it can use alternate sources of fuel.

In this case, we’re talking about lack of glucose (carbs) as a factor and the adaptation in turn, which is namely the body’s ability to metabolize fats and use the ketones it produces, as fuel.

However, it is worth noting here that most ORGANS can use ketones, BUT… The brain mainly relies on glucose.

That is to say that the brain always uses glucose to a certain extent, as the body can produce it, even if we are eating on a low carb diet. (1)

This process of glucose synthesis during a lack of carbohydrates is referred to as “gluconeogenesis” and it involves the use of proteins to synthesize glucose.

Now, the ketogenic diet implies a low carbohydrate intake (basically zero), and a higher protein & fat intake.

That in turn, kicks the body into ketosis and it starts using fat as the primary source of fuel.

Without making it complicated, we’d like to mention that the process of ketone synthesis, depends to a big extent on the level of blood sugar & insulin.

Why? Well, because when blood sugar (glucose) levels are low, that tells the body it is time to transition to an alternate source of energy, namely fat.

That is to say that the less glucose you have in the body, the more you will be kicking your body into ketosis.

Who should use the ketogenic diet?

ketogenic diet for diabetes

Well, to put it bluntly – This approach to nutrition is not for everyone.

The ketone levels in the body are pretty low, given that you bring diversity in your nutrition plan.

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BUT, the ketone levels can go higher under some circumstances, such as periods of starvation and/or carbohydrate restriction, as well as during some health conditions like diabetes.

It is worth mentioning here that ketones too can be toxic for the body, which is why their levels must remain normal.

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However, with just the keto diet, odds are you won’t reach a dangerously high level of ketones in the body, simply because it mostly happens to patients with diabetes.

That is to say that if you are a healthy individual, you will hardly reach the toxic levels of ketones.

The ketogenic diet is mainly good and recommended for people that have certain health conditions like diabetes, cancer, epilepsy and migraines. (2)

Training on the keto diet

ketogenic diet training

Alright, we now know that the body can use alternate sources of energy if needed.

But is that optimal when the task at hand is becoming better and better in your day to day workouts?

Well, let’s do some analysis.

We know that the body has 3 main energy pathways that fulfill the demands for energy during physical activities.

The 3 energy pathways

Those 3 main energy pathways are namely:

  1. Anaerobic-Alactic system (Immediate)

With the immediate system, we mainly rely on the storages of Adenosine triphosphate (ATP) & creatine phosphate (CP), to grant energy.

We use these energy reserves during high-intensity, short in duration physical activities, such as a 60 meter sprint

ATP & CP are essentially the purest source of biological energy, as we can use them basically right away.

It is worth noting here that this metabolism does not need oxygen to release energy, hence the name – Anaerobic.

The immediate energy system grants energy for up to 10 seconds of intense work without producing lactic acid (hence, alactate), after which, the body transitions to the next system.

2. Anaerobic-Lactic (Intermediate)

Now, once we deplete the ATP & CP storages, the body needs to find different means of regenerating ATP.

Note that ATP is ultimately the main source of fuel for any and every mental and physical activity, which is why ALL 3 ENERGY SYSTEMS have the main goal of regenerating the ATP. 

So, once we use the currently available ATP and CP via the immediate pathway, the body starts utilizing blood glucose & glycogen, in a process called glycolysis, via the intermediate pathway.

Glycolysis is the process during which the body uses glucose to form the ATP molecule and ultimately grant energy for sustained activity.

So, we can say that the intermediate energy pathway uses glucose as the main source of fuel to regenerate ATP.

This system can sustain short to intermediate bouts of moderate to high intensity activity, such as a 300-400 meter sprint.

Muscle fatigue

Now, an important note here is the fact that when we break down ATP & Glucose for energy, there is an accumulation of hydrogen ions (protons) and pyruvate.

This in fact is what causes that nasty, unpleasant muscle burn & fatigue.

That muscle burn and fatigue is considered by many professionals to be caused by lactic acid.

As a matter of fact however, lactic acid is actually a BUFFER for the burn.

The accumulation of lactic acid is an adaptive reaction of the organism that happens when each pyruvate molecule soaks up protons.

When that happens, it converts to lactic acid (It’s actually lactate, but for the sake of common knowledge, we use the term lactic acid). (3)

To learn more on lactic acid, check out our article – Is LACTIC ACID the prime evil for bodybuilders?

Now off to the third energy system.

  1. Aerobic (long-term)

Now, with the first (immediate) pathway, we can sustain high-intensity activity for a short period of time.

When the ATP & CP run out, intensity naturally drops and we start utilizing blood glucose & muscle glycogen (Stored glucose), via the intermediate pathway.

And past the 90-120 second mark, we kick the body into the third and final energy pathway – Aerobic.

The aerobic pathway is used by the body to sustain low-intensity, long in duration physical activities, such as a 5 kilometer cross run.

This pathway uses muscle & liver glycogen, as well as fats, as the main sources of fuel.

If those are unavailable, proteins can be used as the last resort source of fuel, via the process of gluconeogenesis.

Can you build muscle on the keto diet?

the energy systems of the body

So, we just briefly analyzed the 3 pathways that the body uses to grant energy for sustained physical activity.

Now the question is – What does muscle growth depend on, and is the keto diet good for people, looking to build muscle?

Well, muscle growth is an adaptive reaction of the organism, that occurs when the musculature is subjected to new, previously unknown stress.

To get through that stress, the body needs to optimally release energy.

And while the ketogenic diet is often praised to have a ton of benefits, it may actually not have such when it comes to the training process.

When we drastically decrease the carbohydrate intake, the body goes through a wide variety of physiological changes, which, to some extent affect our workouts.

In other words, making the body use the more calorie-dense fats (9 calories per gram), instead of the easy to use glucose (4 calories per gram), simply makes the energy-releasing processes sub-optimal.

So, with the lower levels of carbohydrates, we deprive the musculature of the glucose that it so much needs to sustain any physical activity longer than 10 seconds.

This simply means that the functionality of the musculature will be sub-optimal, after the 10 second mark, given that you’re on the ketogenic diet.

Why? Well, if you follow the logic of this article, you’d know that during the first 10 seconds, we use ATP & CP.

We use these compounds  via the immediate energy system and after that we switch to blood glucose & muscle glycogen (intermediate).

It is only after the 90-120 second mark that your body will start properly utilizing  ketones and fats for fuel.

In other words, when we decrease our carbohydrate intake, we take the musculature’s ability to perform optimally in the 10-120 second range of physical activity.

What training is keto bad for?

This simply means that the ketogenic diet will be sub-optimal for the following activities:

  • Weight training for muscle growth (More reps & sets longer than 10 seconds)
  • Sprints longer than 10 seconds (200-400 meters)
  • Swimming sprints longer than 10 seconds
  • High-intensity interval training

Now, of course, there are a ton of other sports and physical activities that are best done through utilization of glucose as fuel, but you get the idea – If we’re working in the anaerobic-lactic pathway, keto is a no-no.

Now, of course, each and every body is different, which simply means that the pathways and times presented are just approximate numbers.

Some people may start utilizing glucose right after the 10th second, while others would take twice as much.

That is to say that when you start the ketogenic diet, you should experiment with your training

Keto bodybuilding macros

keto diet macros

When it comes to calculating macros, most professionals start right off the bat, by calculating the mandatory protein intake of 0.8-1 grams per lbs of bodyweight.

That is mainly because the MOST IMPORTANT thing that will determine your body composition is your protein intake.

Proteins are basically the most common substance in the body after water, which is why we like to say that you ARE protein.

This macronutrient supports an array of physiological functions, while also helping the organism grow and adapt.

For all you trainees reading this, it simply means that proper protein intake equals more gains!

This is exactly why we should also strongly consider and tailor our protein intake when we’re on the ketogenic diet.

How much protein to eat on keto?

In a recent research done by the International society of sports nutrition, the optimal intake was revealed.

It was concluded that a regular, consistent intake of 1.5 to 2 grams of protein per KILOGRAM of bodyweight is optimal for active trainees.

However, the more advanced a trainee is, the more intense their workouts are and the more muscle mass they have, the more that intake can go up.

Ultimately, a top-performer would go for up to 2.3 grams of protein per kilogram of lean body mass.

This intake seems to be optimal for both muscle gaining, as well as muscle retention, during a period of fat loss.

Another factor


Now, if you’ve given up on carbohydrates and have decided to transition to the ketogenic diet, but still want to workout, then you can optimize protein intake for the greater good.

As we mentioned, when our diets lack carbohydrates, the body produces the glucose it needs for certain processes.

The synethesis of glucose at absence of carbs is done via the process called “gluconeogenesis”.

As we mentioned GNG (gluconeogenesis) is possible via the transformation of proteins.

Keto athletes can make use of that and increase their protein intake, to support the process of gluconeogenesis.

In doing so, they will grant their muscles the glucose needed to sustain 10-120 seconds of muscular activity.

You should prioritize animal products as your main source of protein.

Those are:

  • Eggs
  • Meat (beef, chicken, pork, etc)
  • High-fat dairy products

To wrap up the recommendations on protein intake during a ketogenic diet, we’ll set them according to the separate goals:

  1. Gaining or just maintaining muscle mass/composition during a keto diet

When this is the goal at hand, then your optimal protein intake would be around 1 gram per lbs (2.2 per kilogram) of LEAN body weight.

2. Retaining muscle mass during a shredding period

When this is the goal at hand, the protein intake can be slightly higher – Up to 1,3 grams per lbs (3 grams per kilogram) of LEAN body weight.

Note that such high levels of protein intake are mostly recommended for advanced athletes.

If you are new to training, the recommendations of 1 gram per lbs of lean body weight will be just enough.

How much carbs to eat on keto?

Okay, so the ketogenic diet implies cutting out the carbohydrates completely, sooo…

I guess we should not talk about them as a macronutrient?

Well, that’s not really the case. As we’ve mentioned before, the body adapts gradually and doesn’t like drastic changes.

That is to say that during the initial phase, you should gradually decrease your carbohydrate intake.

You do so until you reach a point where you are consuming 35 grams or less, per day.

Now, if you are more active, you can bump that number up slightly, as that will only improve your workouts.

After all, you’re looking for optimal training performance, rather than wonders of magic (some people claim keto works like magic).

Get some carbs in if your workouts consist of high-intensity, short-burst movements that last more than 10 seconds.

To optimize your physical performance during bouts of intense weight training, you can implement 35 to 50 grams of carbohydrates on training days, 30 to 60 minutes before the workout.

It is recommended that you load up with quality carbohydrates, such as rice & oats.

Note that if you’re on the ketogenic diet, some aspects of performance won’t be hindered.

And so, if you don’t particularly focus on weight-training, but rather endurance training, the lack of carbohydrates won’t be bad.


Well, because of something that we learned earlier.

The body uses the Aerobic energy pathway to grant energy for endurance, low-intensity, long duration workouts.

And the aerobic system is keto friendly, as it can use fat (ketones) as the primary source of fuel.

To sum it up

  • If you mainly train for strength (<10 seconds sets of ~5 reps, immediate pathway), the ketogenic diet won’t severely impact your performance
  • If you mainly train for hypertrophy (>10 second sets of 6+ reps, intermediate pathway), the ketogenic diet will negatively impact your performance and it will be sub-optimal
  • If you mainly train for endurance (>120 seconds, aerobic, long-term pathway), the ketogenic diet won’t negatively impact your performance and furthermore, it can even improve it.

Last but not least…

How much fat to eat on keto?

high fat foods

Now, as we learned, keto implies that we will use fats as the main source of energy.

This is exactly why our fat intake with this nutrition regimen is of prime importance, along with proteins.

The results we want to achieve are strictly dependent on the amount of food we are going to eat.

What this means is that the more food we consume, the more weight we will gain.

The same is true in the opposite context – The less food we consume, the more fat and muscle we lose.

However, finding the right ratio of all 3 macronutrients is of prime importance.

This is what will be the factor that will determine your body composition, change of weight and last but not least, mood & satiety.

Most keto experts recommend that you get at least 65% of your daily caloric intake from fats.

That number may go up, depending on the goal you have.

To put it simply, this means that if you are trying to stack muscle mass, you need to create a surplus (excess) of calories.

Keto & muscle growth

We know that muscle growth occurs optimally at a surplus (5).

For you, this simply means that you have to bump up the fat intake so that you are at a slight surplus

Note that we need to control the surplus, as too big of a surplus may result in an excess of fat gains.

Of course, this is the last thing that we want, as excessive fat gains will make us diet (lose muscle) for longer.

We generally recommend you to be at a surplus of 250 to 350 calories per day, that will allow for a lean bulk with zero to none fat gains.

The same thing is relevant for fat loss, where you are looking to create a deficit of energy.

Too big of a deficit will cause muscle loss, which is why we need to bump up protein intake.

Of course, we need to make sure we are also keeping the deficit at 300-500 calories per day.

And so, let’s sum it up:

  • With the keto diet, about 65 to 80% of the daily energy intake should come from fats
  • If you are looking to gain, bump that number up until you are at a surplus of ~350 calories per day
  • If you are looking to lose fat and maintain muscle, stay at a daily deficit of ~500 calories, in order to sustain muscle mass

Keto diet bodybuilding results

jason wittrock results

So, now you are probably wondering – Has anyone succeeded with bodybuilding and keto?

Well, the answer is simple – Yes!

Some people have done it, but it was only possible through careful planning, monitoring and adjusting.

One of the more famous athletes is Jason Wittrock, whose YouTube channel you can find HERE.

Is keto bad for bodybuilding ?

Well, we made sure to shed some knowledge in this article – We talked about the pathways that the body uses to grant energy for certain types of activities.

By explaining that, we made it clear that keto is simply sub-optimal when it comes to purely bodybuilding oriented workouts.

This is because bodybuilding-oriented workouts use the Anaerobic-Lactic energy pathway, which utilizes glucose (carbs).

That is precisely why we can say that keto is NOT inherently bad for bodybuilding, if you implement it correctly.

There is a correct implementation of the keto approach, when the task at hand is optimal bodybuilding results

That is namely including up to 50 grams of carbohydrates on training days, ~60 minutes before a workout.

It is worth noting that bodybuilding style weight workouts are not really excessively glycogen-depleting

This means that they only use a part of your glycogen storages – About 25% to be precise.

This simply means that you won’t really need to do excessive carb loads while on the keto diet.

Ultimately, you should be looking for a proper ratio of all 3 macronutrients.

This will allow you to sustain mental and physical activities, while also maintaining good mood.

Last but not least, the way you structure your diet must allow you to be able to adhere to it in the long term.

If the diet feels like a torture and hinders your physical performance, you should change it.






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