People have been using keto to lose weight for the past 200 years. For example, in the 1970s, it saw a surge in popularity because of the Atkins Diet, which started with a strict ketogenic phase.
During that same time period, bodybuilders have leaned towards higher-carb diets. Conventional bulking diets get most of their calories from carb-rich foods like rice, potatoes, sweet potatoes, oats, bananas, yogurt, beans, and lentils.
What happens if you try to use a ketogenic diet to build muscle? Will it hinder muscle growth? Can it yield leaner gains?
- What is Keto?
- Why Cut Back on Carbs?
- How Does Keto Affect Weight Training & Muscle Growth?
- How Do Carbohydrates Affect Muscle Growth?
- Does Keto Reduce Fat Gain While Building Muscle?
- Are There Advantages to Building Muscle on Keto?
- What Happens If You Bulk On Keto?
- What About the Other Keto Bulking Study
- Summarising the Research on Keto & Muscle Growth
- How to Eat a Ketogenic Bulking Diet
What is Keto?
What is the ketogenic diet? The ketogenic diet is a high-fat, moderate protein, and very-low-carb diet based around eating plenty of meats, eggs, cheeses, nuts, avocados, oils, and fibrous vegetables. For example, a meal might be a fatty cut of steak with a large portion of salad drizzled in olive oil.
What is the ketogenic bulking diet? Since this article is about how a ketogenic bulking diet performs against a traditional muscle-building diet, we’re going to use the best versions of both:
- Standard bulking macros: 25% of calories from fat, 55% from carbs, 20% protein
- Ketogenic bulking macros: 75% of calories from fat, 5% from carbs, 20% protein
Both of these diets have the perfect amount of protein, it’s just that one is high in carbohydrates, the other has almost none.
Why Cut Back on Carbs?
When you eat carbohydrates, your body breaks them down into a type of sugar called glucose, which the cells in your body use for energy. Your muscles and liver store sugar as glycogen, your blood vessels transport it around as blood sugar, and your brain even runs on sugar.
If you stop eating carbs, though—either by fasting, starving, or eating a ketogenic diet—your body can no longer use sugar as its main fuel source, so it begins breaking down fatty acids into ketone bodies (ketones). Over the course of the next few days, your cells switch over to using these ketones for fuel. This process is called ketosis, the foundation of the ketogenic diet.
What’s the purpose of ketosis? What’s exciting about ketosis is that your body starts burning your body fat for energy. Now, to be clear, any diet that allows you to get into a calorie deficit will allow you to lose fat just as quickly (study, study).
If you eat a high-fat diet, you’ll store more fat and burn more fat. If you eat a high-carb diet, you’ll store less fat and burn less fat. Either way, it balances out in the end. Still, many people like the idea of directly using fatty acids for energy.
The main advantage of the ketogenic diet is that it suppresses appetite, allowing people to feel fuller while eating fewer calories (meta-analysis).
How Does Keto Affect Weight Training & Muscle Growth?
When we lift weights, our muscles run on a carb-based fuel called glycogen. The more glycogen we have in our muscles, the longer we can work out before our muscles run out of fuel. If we switch to a ketogenic diet, fewer carbs are available, so our muscles won’t store as much glycogen as they normally do (study, study). Because our muscles aren’t as pumped full of fuel, they’ll look a little smaller and flatter, and they won’t have as much strength endurance.
Glycogen doesn’t have a big impact on strength training (study, study). There aren’t many reps per set (1–5 reps) and there aren’t many sets per workout. It’s a style of training that doesn’t require much muscle fuel, just muscle strength. However, compared to other types of resistance training, strength training doesn’t stimulate quite as much muscle growth.
If you’re trying to get bigger and stronger, you should do hypertrophy training. That means doing moderate-rep sets, typically in the 6–20 rep range. That helps us lift more total poundage each workout giving us a higher training volume, stimulating more muscle growth, but also digging deeper into our glycogen stores. Thus, having more glycogen becomes an advantage.
Mind you, our muscles store quite a bit of glycogen, and even with hypertrophy training, we won’t run out of glycogen unless we train a single muscle group for several hours in a row. Thing is, we aren’t just trying to avoid running out of glycogen; we’re trying to get the performance-enhancing effects of being absolutely packed full of glycogen.
How Do Carbohydrates Affect Muscle Growth?
Most research shows that the more glycogen we have in our muscles, the more muscle we can build (study, study, study). For instance, having more glycogen in our muscles reduces muscle damage while speeding up muscle growth, allowing us to construct more new muscle tissue (study, study).
Furthermore, weight training stresses our bodies. It’s a good type of stress, but it’s stress nonetheless. Higher-carb diets help manage this stress, keeping our testosterone production higher and our cortisol production lower (study). This is important because having higher testosterone can help us build more muscle more leanly, whereas higher cortisol (a stress hormone) can reduce muscle growth, increase fat storage, and suppress our immune systems.
Finally, there’s insulin, which is used to shuttle nutrients toward fat storage or muscle gain. Both protein and carbs stimulate insulin production, meaning that even a ketogenic diet will produce enough insulin to help you build muscle. However, eating more carbs seems to do a better job of this (study, study).
The muscle-building benefits of carbohydrates are well known, even in the ketogenic communities. That’s why there are carbier versions of the ketogenic diet designed for those trying to build muscle:
- Cyclical Ketogenic Diet (CKD): The cyclical ketogenic diet allows people to load up on carbs 1–2 times per week, allowing them to get some of the muscle-building benefits of a higher-carb diet.
- Targeted Ketogenic Diet (TKD): The targeted ketogenic diet allows people to eat a small number of carbohydrates before working out, allowing them to get some of the performance-enhancing effects of carbohydrates.
However, a recent study found that a conventional bodybuilding diet was better for building muscle, gaining strength, and avoiding fat gain than a cyclical ketogenic diet.
Does Keto Reduce Fat Gain While Building Muscle?
When we’re in a calorie surplus, we have extra nutrients. We can do a few things with those surplus nutrients:
- Carbs can easily be stored as muscle glycogen, improving lifting performance and muscle growth
- Protein can be burned off as body heat and used to build muscle
- Fat can easily be stored as body fat
Protein and carbs can be converted into fat (de novo lipogenesis), but it’s rare and inefficient. What usually happens is that we use the protein and carbs, then save some of the fat. We all eat some fat, so we all have fat to set aside. Still, bulking diets higher in protein and carbs may yield slightly leaner gains than those higher in fat (study).
Are There Advantages to Building Muscle on Keto?
Most people doing keto aren’t interested in building muscle; they’re interested in losing weight. The reason they love keto is that it suppresses their appetite. This doesn’t always interfere with muscle growth. Overweight people have extra energy in their extra fat, so they can often build muscle even while losing weight.
If you’re a skinny guy who’s trying to bulk up, appetite suppression can be a real problem. Eating a big bulking diet is already hard. Keto only makes it harder.
It’s especially hard during the first month or two of keto. Your body won’t be used to digesting so much fat, which can cause indigestion. It’s also common to feel fatigued, known as the “keto flu.” After adapting to the diet, it becomes a little easier to eat more calories. But it’s never as easy as bulking with a more balanced diet.
What Happens If You Bulk On Keto?
Until recently, there was only one high-quality study investigating what happens if you bulk on a ketogenic diet. The results are interesting. Not surprising, but interesting.
The researchers split the study participants into a ketogenic group and a high-carb group:
- High-Carb: 25% from fat, ~55% carbs, 2g/kg protein
- Ketogenic: ~70% fat, less than 10% carbs, 2g/kg protein
Both groups were put on a 4-day/week lifting program. Both groups were put on a high-calorie bulking diet. After eight weeks, here’s what happened:
- High Carb: +3 pounds muscle, -1 pound fat
- Ketogenic: -1 pound muscle, -2 pounds fat
The high-carb group gained a substantial amount of muscle while losing some fat. That might not seem like much muscle growth in 8 weeks, but these were experienced lifters, so that’s to be expected.
The ketogenic group lost muscle, so the researchers (perhaps mistakenly) concluded that ketogenic diets weren’t good for building muscle. However, their failure to consume enough calories could easily explain their failure to build muscle. Despite their best efforts, they weren’t bulking. They were cutting.
It’s never wise to put all of your faith in a single study, but there’s a growing body of evidence with similar findings:
- A case study found that after switching to a ketogenic diet, four out of the five lifters stopped gaining muscle mass. One of the researchers, Eric Helms, PhD, commented that “if your goal is to put on muscle mass, it’s probably best to have some level of carbohydrate in your diet.” Based on his review of the research, he recommends a bare minimum of one gram of carbs per pound bodyweight per day.
- In a study on CrossFitters, the ketogenic group lost muscle. The control group gained muscle.
- A couple of other studies found that when strength athletes stopped gaining muscle when they switched to a ketogenic diet.
However, these studies mainly show that ketogenic diets suppress appetite. On average, the participants failed to gain weight. They weren’t able to bulk. So we don’t actually know what happens when people bulk on a ketogenic diet.
What About the Other Keto Bulking Study
Since we’re talking about bulking on a ketogenic diet, we should probably mention the elephant in the room. One study found that keto caused rapid muscle growth (study). This study is somewhat suspect, but let’s start by breaking it down.
The researchers split the participants into two groups:
- High-Carb: 25% from fat, 55% carbs, 20% protein
- Ketogenic: 75% fat, 5% carbs, 20% protein
After 11 weeks of doing a 3-day/week lifting program, their results were:
- High-Carb: +4.8 pounds of muscle, -3.3 pounds of fat
- Ketogenic: +9.5 pounds of muscle, -4.8 pounds of fat
That’s quite a lot of muscle growth, but that’s not why the study is dubious. As we covered in our newbie gains article, plenty of studies find tremendous rates of muscle growth, especially in untrained lifters:
- This study on beginners found that guys could gain 9 pounds of muscle during their first 8 weeks of working out.
- In this study, a group of untrained beginners gained an average of 12 pounds of muscle during their first 10 weeks of working out.
- In another study, beginners gained 15 pounds of muscle during their first 12 weeks of lifting weights.
Some people can build muscle when they bulk aggressively. If someone’s workout program and lifestyle are good enough, perhaps the ketogenic diet can produce those same results.
Here’s where the controversy begins. This study is just a one-page summary of research that isn’t available anywhere. Moreover, these are the same researchers that published a controversial study on HMB, showing that it produced more muscle growth than high doses of steroids. Those results couldn’t be reproduced by other researchers (study).
The literature surrounding ketogenic diets and muscle growth is still nascent and has methodological issues that prevent us from drawing any real meaningful conclusions. Currently, from my perspective, there isn’t much data one can use to suggest it is superior to other approaches or to show it is not inferior to other approachesBrad Dieter, PhD
Overall, I think it’s wise to be skeptical of any single study. Especially suspicious studies like this one. If other researchers can’t reproduce the results, you probably can’t, either. Fortunately, since this article was originally published, more research has emerged. Let’s dive even deeper.
Summarising the Research on Keto & Muscle Growth
The Schoenfeld Keto Study
Dr. Brad Schoenfeld recently conducted his own research into whether ketogenic diets were effective for building muscle. His study found, in keeping with the overall body of evidence, that ketogenic diets weren’t ideal for building muscle. One of the main reasons the ketogenic diet failed to produce much muscle growth was because the participants failed to get into a calorie surplus.
Dr Schoenfeld summarized these findings by saying, “when considering this study in context with the body of literature, a general take-home would be that the keto diet is a viable strategy for losing body fat, but would not be ideal if your goals are to maximize strength and hypertrophy.”
The Vargas-Molina Keto Study
We also have a 2020 study from Vargas-Molina and colleagues showing that, once again, the keto bulkers struggled to eat enough food to support muscle growth. However, even if the keto participants had gotten into a calorie surplus, hypertrophy training tends to be done in moderate-to-high rep ranges, which benefits from having plenty of glycogen in our muscles. Keto diets tend to reduce the glycogen we store in our muscles. As a result, the non-keto group gained significantly more muscle size and strength than the keto group.
The current evidence doesn’t suggest that it’s impossible to gain muscle on a ketogenic diet, but its effects on appetite and high-intensity exercise performance make it hard to view keto as the ideal dietary approach for gaining muscle.Eric Trexler, PhD
The Adam Tzur Study: The Ketogenic Diet’s Effect on Bodybuilders
A 2020 study by Adam Tzur and Brandon Roberts, PhD, found that ketogenic diets reduce glycogen storage. They concluded that keto is “suboptimal for bulking and gaining lean mass.”
The Paoli Study: Keto vs Conventional Bodybuilding Diets
The most recent study pitting the ketogenic diet against a conventional bodybuilding diet is a 2021 paper by Paoli et al. Some participants ate a ketogenic diet, getting just 5% of their calories from carbohydrates. The others were put on a conventional bodybuilding diet, getting 55% of their calories from carbohydrates. The keto group had trouble eating enough calories and struggled to build muscle.
This study brings up an interesting point, though. Our muscles store less glycogen when we eat fewer carbohydrates, causing our muscles to deflate. This doesn’t necessarily mean we have less contractile tissue, though, just that our muscles aren’t as pumped full of glycogen. Perhaps the ketogenic bulkers are gaining contractile tissue, just losing glycogen.
How to Eat a Ketogenic Bulking Diet
Even if keto isn’t ideal for building muscle, there are other reasons why someone might want to follow a ketogenic diet. Maybe they’re having trouble digesting carbs. Maybe they’re struggling to control their ravenous appetite. Maybe they simply prefer it.
Here’s how to eat a healthy ketogenic diet that supports muscle growth:
- Eat enough calories to gain weight: for a beginner, we usually recommend gaining about a pound every week, which means eating around 500 extra calories each day (which is usually a total of around 18–22 calories per pound body weight per day). If a week goes by and you don’t gain weight, add another 200 daily calories. Adjusting every week will allow you to keep gaining weight even as your metabolism adapts to your bulking diet. For more experienced lifters, gaining 0.5 pounds per week usually works better.
- Eat enough protein (0.8g/lb/day): eating around 0.8 grams of protein per day should allow you to build muscle at a maximal pace while having no trouble staying in ketosis. This is usually pretty easy while on a ketogenic diet, and most guys doing keto naturally eat enough protein for muscle growth.
- Eat mostly whole foods: on a ketogenic diet, this usually means eating lots of unprocessed meat, dairy, eggs, nuts, seeds, avocados, very dark chocolate, and tons of fibrous vegetables. Watch out for letting your saturated fat intake rise above 10% of your total calories. That usually means getting most of your fat from nuts, seeds, avocadoes, olives, and olive oil. Avocado oil tends to make for the best cooking oil.
- Eat a diet that’s easy on the appetite and easy to digest: You might want to lean towards ground meat, which is easier to chew and digest, making it easier to get into a calorie surplus. Use high-calorie condiments like aioli and mayonnaise (made from ingredients like olive oil, eggs, garlic, mustard, and vinegar). Drizzle your salads with plenty of olive oil.
The main challenge of bulking on a ketogenic diet is eating enough calories to gain weight. However, there are ways around that. Here’s our guide for how to eat more calories. It’s not specific to the ketogenic diet, but the same principles apply.
Most people lose weight while eating a ketogenic diet, severely limiting muscle growth. Even if you can eat enough calories to gain weight, you’d still build muscle faster and more leanly by including more carbs in your bulking diet.
If you choose to bulk on a ketogenic diet, make sure you’re eating in a calorie surplus—that you’re gradually gaining weight. For most skinny guys, that means gaining 0.5–1 pound per week.
If you want more muscle-building information, we have a free bulking newsletter for skinny guys. If you want a full bulking program, including a 5-month workout routine, diet guide, recipe book, and online coaching, check out our Bony to Beastly Bulking Program. Or, if you want an intermediate bulking routine, check out our Outlift Intermediate Bulking Program.