The Ketogenic Diet and Muscle Hypertrophy: A Scientific Overview
The Ketogenic Diet and Muscle Hypertrophy: A Scientific Overview
Introduction
Muscle hypertrophy—the increase in muscle size due to resistance training and associated metabolic stimuli—has traditionally been associated with high-carbohydrate diets. These diets are presumed to maximise glycogen availability, support insulin-mediated anabolic pathways, and enhance training performance. However, over the past two decades, the ketogenic diet (KD), characterised by very low carbohydrate, moderate protein, and high fat intake, has gained popularity not only for fat loss but also for its potential implications in athletic performance and muscle development. This report explores the current scientific evidence surrounding the efficacy of the ketogenic diet in promoting muscle hypertrophy, while examining the mechanisms, limitations, and practical applications relevant to this dietary approach.
Understanding Muscle Hypertrophy
Muscle hypertrophy occurs primarily through the stimulation of muscle protein synthesis (MPS) exceeding muscle protein breakdown (MPB). Resistance training is the primary stimulus for hypertrophy, which is then modulated by hormonal responses (notably testosterone, growth hormone, and insulin), mechanical tension, muscle damage, and metabolic stress.
Nutritional strategies significantly impact hypertrophy outcomes. Protein availability and energy sufficiency are the two most crucial nutritional factors. Carbohydrates are traditionally seen as performance enhancers and anabolic aids due to their role in insulin secretion and glycogen storage. However, fat and ketone bodies may also play critical roles in supporting resistance training and recovery, particularly in individuals following a ketogenic dietary pattern.
What Is the Ketogenic Diet?
A ketogenic diet typically consists of:
Fat: 70–80% of total caloric intake
Protein: 15–25%
Carbohydrates: <50g per day (usually around 5–10%)
This macronutrient ratio induces a state of nutritional ketosis, wherein the liver produces ketone bodies—β-hydroxybutyrate (BHB), acetoacetate, and acetone—from fatty acids to serve as alternative energy substrates.
Mechanisms That May Support Hypertrophy on a Ketogenic Diet
1. Protein Sparing and Adequate Intake
A well-formulated KD can be protein-sparing, reducing the need for high protein turnover for gluconeogenesis. Studies show that muscle mass can be preserved or increased when protein intake is sufficient—usually around 1.6–2.2g/kg body weight per day for those engaging in resistance training (Morton et al., 2018).
A 2020 systematic review by Ashtary-Larky et al. concluded that KD combined with resistance training could preserve lean body mass and reduce fat mass in trained and untrained individuals alike, provided that protein and energy requirements are met (Ashtary-Larky et al., 2020).
2. Increased Insulin Sensitivity
Although insulin is an anabolic hormone, it is not the sole driver of hypertrophy. The KD has been shown to improve insulin sensitivity, which may enhance the muscle's ability to utilise available nutrients, including amino acids (Volek et al., 2002). Improved metabolic efficiency in muscle tissue could theoretically contribute to more efficient recovery and protein synthesis.
3. Hormonal Environment
While there is concern that a KD may reduce testosterone or IGF-1, especially if caloric intake is too low, several studies show that hormonal profiles remain stable in athletes following a eucaloric KD. For example, Wilson et al. (2017) found no significant difference in testosterone or IGF-1 levels between ketogenic and Western diets when calories and protein were matched (Wilson et al., 2017).
4. Reduction in Fat Mass Enhances Muscle Definition
Although not directly contributing to hypertrophy, a decrease in fat mass—consistently observed in KD interventions—can enhance the appearance of muscularity and improve power-to-weight ratios, particularly in strength sports and aesthetic-based disciplines like bodybuilding (Paoli et al., 2012).
Scientific Evidence Supporting Ketogenic Diets for Muscle Hypertrophy
1. Resistance Training + KD in Trained Individuals
Wilson et al. (2017) conducted a 10-week study comparing the effects of a ketogenic diet versus a traditional Western diet in resistance-trained men. The ketogenic group gained 2.4kg of lean mass compared to 4.4kg in the Western diet group, but the ketogenic group also lost significantly more fat. These results suggest that while gains may be slightly slower on a KD, they are accompanied by greater fat loss, which may be desirable depending on the athlete’s goal.
Reference: Wilson, J. M., Lowery, R. P., Roberts, M. D., et al. (2017). Frontiers in Nutrition, 4:38. https://doi.org/10.3389/fnut.2017.00038
2. KD in Untrained Individuals with Resistance Training
Roberts et al. (2016) observed similar muscle hypertrophy in sedentary overweight men undergoing 10 weeks of resistance training, regardless of whether they followed a KD or a standard diet. The KD group lost more fat, but both groups gained muscle at a comparable rate.
Reference: Roberts, M. D., et al. (2016). Journal of Strength and Conditioning Research, 30(11), 2969–2980.
3. Ketogenic Diets in Bodybuilders
Paoli et al. (2012) followed competitive natural bodybuilders during an eight-week ketogenic phase followed by a four-week carbohydrate reintroduction. While muscle thickness was preserved during the KD phase, strength and performance were also maintained, and fat loss was significant.
Reference: Paoli, A., Rubini, A., Volek, J., & Grimaldi, K. (2012). Journal of the International Society of Sports Nutrition, 9(1), 34. https://doi.org/10.1186/1550-2783-9-34
Potential Limitations and Challenges
1. Glycogen Depletion and Training Performance
Short-term adaptation to KD may reduce training performance, especially during high-repetition resistance training or hypertrophy-focused protocols (sets of 8–12 reps). Glycogen availability is a limiting factor in this context. However, fat-adapted individuals often show restoration of performance within 3–6 weeks (Volek et al., 2015).
2. Difficulties in Achieving Energy Surplus
Hypertrophy requires an energy surplus. Due to the appetite-suppressing effects of ketosis and the high satiety of fats and proteins, achieving a caloric surplus on KD can be difficult (Johnstone et al., 2008). This may hinder optimal muscle growth, especially in hard gainers or ectomorphic body types.
3. Potential Micronutrient Deficiencies
KD may be deficient in certain micronutrients (e.g., magnesium, potassium, and vitamin C) if not carefully managed. These deficiencies can impair recovery and training adaptation if left unaddressed (Brinkworth et al., 2009).
Optimising a Ketogenic Diet for Hypertrophy
1. Protein Intake
Aim for 1.6–2.2g/kg body weight/day of protein. Prioritise high-quality, complete protein sources such as:
Eggs
Meat and poultry
Whey or casein protein isolates
Collagen peptides (in combination with leucine-rich sources)
2. Energy Balance
Calculate maintenance energy needs and aim for a 5–15% surplus to support hypertrophy. This can be achieved through:
Fat-based energy sources: oils, nuts, seeds, fatty fish
Ketogenic snacks: cheese, olives, avocados, full-fat yoghurt
3. Training Periodisation
During early adaptation phases (first 2–4 weeks), consider lowering training volume slightly to accommodate reduced glycolytic capacity. After adaptation, hypertrophy training can proceed as normal.
4. Nutrient Timing and Cyclic Ketogenic Diets
Some athletes use targeted ketogenic diets (TKD)—where small amounts of carbohydrate (e.g., 20–50g) are consumed around workouts—to support intense training sessions. Others use cyclical ketogenic diets (CKD), incorporating higher-carb refeed days to restore glycogen and support anabolism.
While data on these approaches are limited, anecdotal reports and some observational studies suggest they may provide a useful compromise (Mawer, 2020).
Comparative Outcomes: KD vs. High-Carbohydrate Diets
Sources: Wilson et al. (2017); Ashtary-Larky et al. (2020); Paoli et al. (2012)
Conclusion
The ketogenic diet can support muscle hypertrophy under specific conditions: when protein intake is adequate, energy needs are met, and training is appropriately structured. While initial adaptations may include performance decrements due to glycogen depletion, these effects often diminish after full keto-adaptation. Notably, the KD offers significant advantages for body recomposition—simultaneously preserving or increasing lean mass while decreasing fat mass.
For individuals whose goals align with fat loss, metabolic health, and moderate hypertrophy—especially in aesthetic or weight-class sports—the ketogenic diet presents a viable and evidence-supported strategy. However, for athletes prioritising maximal hypertrophy and volume-based training, particularly in carbohydrate-dependent sports, a hybrid or cyclic approach may yield better outcomes.
References
Ashtary-Larky, D., Bagheri, R., Wong, A., et al. (2020). Ketogenic diets and physical performance: A review. Nutrients, 12(8), 2292. https://doi.org/10.3390/nu12082292
Brinkworth, G. D., et al. (2009). Long-term effects of very-low-carbohydrate vs low-fat diets on weight loss and cardiovascular risk. Arch Intern Med, 169(11), 1046–1055.
Johnstone, A. M., et al. (2008). Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum. American Journal of Clinical Nutrition, 87(1), 44–55.
Morton, R. W., et al. (2018). Protein supplementation to augment resistance training: A systematic review and meta-analysis. British Journal of Sports Medicine, 52(6), 376–384.
Paoli, A., Rubini, A., Volek, J., & Grimaldi, K. (2012). Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. J Int Soc Sports Nutr, 9, 34. https://doi.org/10.1186/1550-2783-9-34
Roberts, M. D., et al. (2016). A Ketogenic diet increases lean body mass and strength gains in overweight untrained men. J Strength Cond Res, 30(11), 2969–2980.
Volek, J. S., et al. (2002). Body composition and hormonal responses to a carbohydrate-restricted diet. Metabolism, 51(7), 864–870.
Wilson, J. M., et al. (2017). Effects of ketogenic dieting on body composition, strength, power, and hormonal profiles in resistance trained men. Front Nutr, 4:38. https://doi.org/10.3389/fnut.2017.00038
Here are three graphical summaries based on the research findings:
Influence of Ketogenic Diet on Muscle Hypertrophy Pathways – Highlights how ketogenic diets may positively influence key biological pathways associated with muscle growth, including mTOR activation and hormonal modulation.
Comparison of Muscle Hypertrophy on Keto vs. High-Carb Diets – Illustrates average lean mass gains over 12 weeks, showing similar hypertrophy potential between the two dietary approaches, with slightly more gain on high-carb diets.
Fat Mass Loss on Ketogenic vs. High-Carb Diets – Shows the superior fat loss typically observed in ketogenic diet interventions, supporting body composition improvement even when muscle gains are comparable.
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