By Craig Clarke & the Ruled.me team – Your body composition is largely determined by three factors: diet, exercise, and lifestyle. The cumulative effect of each factor is reflected in the mirror via the location and quantity of your muscle and fat tissue.
Simply by following the right diet, you can gain a significant amount of control over your body weight, body fat %, and muscle mass. Emerging evidence indicates that the keto diet has unique advantages that may make it an ideal dietary strategy for achieving a lean muscular physique.
However, before you cut the carbs, it is important to understand how keto works and what you want to focus on to meet your goals.
The Keto Diet and Body Composition: A Quick Research Review
First, let’s take a look at the bigger picture. There is a great deal of skepticism surrounding keto, and this is largely the result of what happens when we only consider the average trend of the data.
In 2017, SCI-FIT published an extensive review of scientific literature exploring how the ketogenic diet affects body fat, muscle mass, strength, and endurance. On average, the keto diet was found to be as effective as other diets for fat loss with the tendency for more lean body mass to be lost as well. 
On a mechanistic level, most of the fat loss was the result of a calorie deficit, while the trend toward lean body mass loss was mostly due to water loss and lower glycogen levels. Carb restricted diets also have been found to stimulate a slightly larger proportion of visceral fat loss (commonly known as a “beer belly” or “stubborn stomach fat”) than low-fat diets.
If we were to stop here with this brief data summary, the case for using the keto diet isn’t very convincing. However, there is a lot more to keto that this broad view blurs out.
The Unique Advantages of Keto Diet for Body Transformation
When we take a closer look at the individual data and our current mechanistic understanding of ketosis, several unique advantages emerge:
To lose fat, you must consume less energy than you use throughout the day. Unfortunately, your efforts to lean out your physique will often be met by increased hunger and cravings.
One way to keep the hunger from provoking a binge is by restricting carbs and maintaining ketosis. By limiting carb intake, you will naturally consume more highly satiating meals and cut out many of the foods that stimulate appetite. If you restrict carbs low enough, your body will produce significant amounts of ketones, which have been found to suppress appetite as well.
The result of this dual effect is that many keto dieters feel more satiated after eating less food than before. According to a research review of 11 keto diet studies, participants ate about 600 kcal less than their regular diet on average.  Depending on the calorie deficit this creates, this can yield up to ~1 pound of body fat loss per week.
Preservation of Muscle Mass
One of the biggest risks of losing fat is that muscle will be lost along with it. Three of the most heavily relied upon strategies to combat this are eating enough protein, following a slight caloric deficit, and continuing to resistance train. Fortunately, the extensive research on keto diets, ketones, and ketosis may have uncovered another: increasing ketone levels.
One human study, in particular, found that beta-hydroxybutyrate — the most efficient ketone body, often referred to as BHB — decreased muscle breakdown and even promoted muscle protein synthesis. This effect is astonishing, especially when you consider the fact that the researchers used relatively low levels of BHB compared to what humans typically have in circulation during fasting. 
Unfortunately, it is unlikely that having higher blood ketone levels will help build significant amounts of muscle. At most, BHB may help decrease the likelihood that your muscle proteins will be used for fuel while you are losing fat.
Improved Energy Levels
As your body adapts to the keto diet, you may notice a decrease in fatigue and enhancement in overall energy, especially during low-moderate intensity activities. This is thought to be the result of burning more ketones for fuel than usual.
If you experience more fatigue when you are in a calorie deficit, the keto diet may be a game-changer for you, especially when you consider its many science-backed benefits.
Practical Application: How to Use Keto for Fat Loss and Muscle Growth
Now that you know the advantages of keto, let’s take a look at how we can harness them to transform your body. Here are some simple guidelines to follow when putting them into practice:
Restrict Carbs Low Enough to Enter and Sustain Ketosis
Limiting your carb consumption to stimulate consistent ketone production is crucial if you want to reap the benefits of hunger reduction and muscle preservation. A good starting point is consuming fewer than 35 grams of total carbs and 25 grams of net carbs per day. (Net carbs are found by subtracting the grams of fiber from the total grams of carbs.)
Depending on your activity levels, you may be able to incorporate more carbs without knocking yourself out of ketosis. Finding your personal ketogenic diet carb limit, however, requires specific tools and some trial and error that extend beyond the scope of this article. For an exhaustive guide, go here.
Prioritize Adequate Protein Intake
Protein consumption is crucial for muscle growth. Without eating an adequate amount, you will get subpar results from your workouts.
Your ideal protein intake will vary depending on your goals, body fat %, training experience, and overall calorie intake.
If your primary goal is to decrease body fat %, the current literature points toward 2.3-3.1g/kg of fat-free mass (~1-1.4 g/lb of fat-free mass) as being the range to aim for.  The higher end of this range is recommended for anyone who has a relatively low body fat % or is undergoing severe calorie restriction. The lower end of the range tends to be sufficient for gentle calorie deficits, higher body fat percentages, and those with minimal training experience.
If your primary goal is to gain muscle mass, a recent research review indicates that ~1.6 g/ kg per day (~0.7 g/lb) is sufficient to maximize muscle growth, assuming you are eating a mild calorie surplus.  However, some studies indicate that a protein intake of more than 2.2 g/k/d and perhaps as high as 3.4 g/kg/d (1-1.5 g/lb) may be best for minimizing fat gain. 
The research literature also suggests that consuming enough protein throughout the day is much more important than when you consume it. Following specific nutrient timing strategies plays a minor role. 
Eat Plenty of Fat, but Not Too Much
While following a keto diet, dietary fat will be your primary source of calories. This means that fat consumption will be the ultimate dietary determinant of whether you gain or lose fat.
If you eat so much fat that you put yourself in a calorie surplus, your body will end up storing the excess energy as fat. Conversely, if you eat so little that you are in a severe calorie deficit, the likelihood that you break down precious dietary protein and muscle for fuel will increase.
This is where using a ketogenic diet calculator is crucial. It will help you get a rough estimate of the fat intake to aim for to meet your body composition goals.
However, make sure you keep these principles in mind before you calculate your macronutrient needs:
- The steeper your calorie deficit, the more you will bias your body towards using protein (from muscle and meals) for fuel instead of building muscle.
- Those with minimal training experience and/or higher body fat percentages can usually handle a larger calorie deficit without losing a significant amount of muscle mass. These populations are more likely to gain significant amounts of muscle while losing fat as well.
- As you accumulate more training experience and lose body fat, the likelihood that you can stay in a calorie deficit and gain muscle at the same time will decrease.
- Regardless of how much body fat or training experience you have, muscle growth is optimized when you are in a slight calorie surplus and consuming enough protein.
Assess Your Progress Monthly and Make Small Adjustments
Tracking simple proxy measures — such as waist circumference, the circumference of the muscular regions you want to grow, your weight, and basic blood work with your physician — will make it easier for you to tell if your health and body composition are trending in the right direction.
Give yourself at least 4 weeks of following your new keto strategy before making adjustments. Reassess every month, adapt, and repeat.
However, I don’t recommend using only one measurement, as it can be misleading. You’ll want to use multiple measures of different aspects of health and body composition to paint a better picture of your results.
For example, if your waist circumference is going up while your other circumference measurements are going down, then you are probably gaining fat and losing lean body mass. This indicates that you may need to increase protein intake and decrease fat intake (assuming you are working out with enough volume to stimulate muscle growth).
Keto for Contest Prep — Dropping Water Weight Without Starvation
The keto diet also provides us with a simple way to shed off a significant amount of water weight while preserving precious muscle gains. This makes it one of the healthiest strategies for those of you who need to fit within a specific weight class for competition.
During the first day of the ketogenic diet, your main fuel source becomes the stored glycogen from your liver and muscle. Since water is stored along with glycogen, you can lose up to1.5 lb of water weight after the first 1-2 days of carb restriction.
As you continue to follow keto, your insulin levels will decrease significantly as well. Not only will this promote fat utilization, but it will trigger sodium excretion.  When sodium releases, it takes water along with it.
Overall, this combination of glycogen depletion and sodium loss can yield up to 10 pounds of weight loss after just 5 days of following the keto diet.
However, the amount of water weight loss depends on the person. To find out if this strategy will be effective for you, try testing it out several months before your competition and track how much weight you lose throughout the week.
After you use this strategy to make weight, make sure you rehydrate and increase your intake of sodium, potassium, and magnesium to help remedy or prevent keto flu symptoms (many of which are caused by excess water and mineral loss).
One Caveat for Keto: Bulking with a Suppressed Appetite
One of the dietary principles we must follow while on a bulk (i.e., optimizing our diet for maximum muscle gain) is to be in a calorie surplus. If you’ve already implemented a bulking cycle before, you may be all too familiar with how hard it can be to constantly overeat without the help of processed carbs and sugary foods.
While on a keto diet, this struggle is magnified for many because of its appetite-suppressing properties. Many studies have found that, even when athletes and lifters are told to be in a calorie surplus on keto, they end up consuming less than they think and losing fat. 
To ensure that you eat enough fat and protein during a carb-restricted bulking phase, I recommend tracking your macronutrient consumption.
If you find it too difficult to bulk with a low carb approach, you can try implementing a cyclical keto diet instead. This is essentially a standard keto diet alternated with a higher carb diet at an interval that fits your current goals and lifestyle.
For example, you could follow a keto diet during your cutting phase (i.e., to maximize fat loss and preserve muscle) and add more carb-rich foods during your bulking phase (i.e., to maximize muscle gain). Another option is to alternate the diets throughout the week by following keto for 5-6 days and eating a higher carb diet for 1-2 days.
Practical Takeaways: Transforming Your Physique with Keto
There are two contexts in which the keto diet has clear advantages over most diets:
- When you want to lose fat and preserve muscle (or gain muscle, in some cases).
- When you want to lose weight rapidly for a competition while minimizing muscle loss.
Conversely, the keto diet’s appetite-suppressing effect can make it harder to bulk (i.e., to maximize muscle gain with your diet). Because of this, you may find it easier to track your macronutrients or follow a cyclical keto diet if bulking is your current goal.
Regardless of what body composition you’re trying to achieve, make sure you follow these simple principles:
- Eat the right amount of calories and protein
- Lift weights with adequate volume to stimulate muscle growth
- Optimize your lifestyle for more movement, better sleep, and less stress
- Assess your progress monthly and make minor adjustments if needed
If you are looking for ideas regarding what you can eat to transform your body, you may find a comprehensive keto meal plan with expert tips and delicious recipes, like our Keto Academy, to be the tool you need to get you on the right track.
- “The Ketogenic Diet’s Impact on Body Fat, Muscle Mass, Strength, and Endurance • Sci-Fit.” Sci-Fit, January 22, 2019. https://sci-fit.net/ketogenic-diet-fat-muscle-performance/
- “How the Ketogenic Diet Affects Hunger (Research Review).” Sci-Fit, April 5, 2018. https://sci-fit.net/ketogenic-diet-hunger-suppression/
- Nair, K S, S L Welle, D Halliday, and R G Campbell. “Effect of Beta-Hydroxybutyrate on Whole-Body Leucine Kinetics and Fractional Mixed Skeletal Muscle Protein Synthesis in Humans.” The Journal of clinical investigation. U.S. National Library of Medicine, July 1988. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC303494/
- Manninen, Anssi H. “Very-Low-Carbohydrate Diets and Preservation of Muscle Mass.” Nutrition & metabolism. BioMed Central, January 31, 2006. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1373635/
- Helms, Eric R, Caryn Zinn, David S Rowlands, and Scott R Brown. “A Systematic Review of Dietary Protein during Caloric Restriction in Resistance Trained Lean Athletes: a Case for Higher Intakes.” International journal of sport nutrition and exercise metabolism. U.S. National Library of Medicine, April 2014. https://www.ncbi.nlm.nih.gov/pubmed/24092765/
- Morton, Robert W, Kevin T Murphy, Sean R McKellar, Brad J Schoenfeld, Menno Henselmans, Eric Helms, Alan A Aragon, et al. “A Systematic Review, Meta-Analysis and Meta-Regression of the Effect of Protein Supplementation on Resistance Training-Induced Gains in Muscle Mass and Strength in Healthy Adults.” British Journal of Sports Medicine. BMJ Publishing Group Ltd and British Association of Sport and Exercise Medicine, March 1, 2018. https://bjsm.bmj.com/content/52/6/376
- Leaf, Alex, and Jose Antonio. “The Effects of Overfeeding on Body Composition: The Role of Macronutrient Composition – A Narrative Review.” International journal of exercise science. Berkeley Electronic Press, December 1, 2017. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5786199/
- DeFronzo, R. A. “The Effect of Insulin on Renal Sodium Metabolism.” SpringerLink. Springer-Verlag, September, 1981. https://link.springer.com/article/10.1007/BF00252649