Impact of the ketogenic diet on body fat, muscle mass, and exercise performance: a review

Article information

Phys Act Nutr. 2023;27(4):1-7

Publication date (electronic) : 2023 December 31

doi : https://doi.org/10.20463/pan.2023.0031

Department of Physical Education, Sangji University, Wonju, Republic of Korea

^*Corresponding author : Nana Chung Department of physical Education, 83 Sangjidae-gil, Wonju- si, Gangwon-do, Republic of Korea. Tel: +82-33-730-0603 E-mail: cnnmms44@sangji.ac.kr

Received 2023 September 4; Revised 2023 November 12; Accepted 2023 November 17.

Abstract

[Purpose]

The purpose of this review was to investigate the effects of the ketogenic diet (KD), on body fat, muscle mass, and exercise performance. As the KD is a subject of ongoing debate, we also present the existing evidence regarding its potential benefits in the aforementioned areas of body fat, muscle mass, and exercise performance.

[Methods]

A literature search was conducted using the keywords “ketogenic diet, low-carbohydrate diet, high-fat diet, body fat, muscle mass, and exercise performance” in PubMed, Web of Science, and Google Scholar.

[Results]

The KD effectively reduced body fat in the short term and, preserved muscle mass during weight loss, however, its impact on exercise performance remains inconclusive owing to various factors.

[Conclusion]

While controversial, it is undeniable that the KD has the potential to affect body fat, muscle mass, and exercise performance. Consequently, additional research is required to elucidate the underlying mechanisms across various populations, optimize their implementation, and understand their long-term effects.

Keywords: ketogenic diet; low-carbohydrate high-fat diet; body fat; muscle mass; exercise performance

INTRODUCTION

Excess body weight is recognized as a fundamental cause of numerous health issues. In addition to assessing weight, the concept of “overfat” or “normal-weight obesity” has emerged, referring to individuals with excessive body fat despite falling within the normal weight range. Surprisingly, a significant proportion of individuals with normal weight, ranging from 20% to 40%, may fall into the category of overfat [1].

While there is a consensus that improving dietary habits and physical activity patterns is crucial for reducing body fat, debates continue regarding the optimal quantity and type of exercise and ideal dietary strategies. Among the various dietary methods proposed for fat reduction, the ketogenic diet (KD) has recently gained popularity. The KD is characterized by low carbohydrate, moderate protein, and high fat intake, with daily energy intake distribution approximately as follows: carbohydrates (5%), protein (20%), and fat (75%) [2].

In a conventional diet, our bodies mainly utilize carbohydrates and fats as primary energy sources. However, when following the KD, a significant metabolic shift occurs. The body transitions from relying on carbohydrates to using fats as the primary energy source, achieved by depleting carbohydrate stores. The central nervous system, specifically the brain, typically relies on glucose as its primary energy source owing to the exclusive utilization of glucose by the blood-brain barrier. This protective barrier prevents the entry of various substances into the brain, including large fatty acids. Consequently, glucose is the primary fuel for the brain [3].

Debates regarding the potential risks associated with the KD center on the brain. After a few days on the KD, one of the brain’s primary energy sources, glycogen, becomes depleted. This depletion can lead to stress and other issues [4-6]. However, proponents of the KD argue that despite the need for an adaptation period, this dietary approach induces a state of ketosis. During ketosis, as fats are broken down, three types of ketone bodies are produced: acetoacetate, ß-Hydroxybutyrate, and acetone. These ketone bodies increase within the body, allowing the brain, heart, muscles, and other tissues to use them as an energy source [7] (Figure 1). These metabolic adaptations have been suggested to promote fat oxidation, leading to favorable body fat level changes, and potentially affecting muscle mass and exercise performance by influencing fuel utilization and metabolic efficiency.

Figure 1.

Metabolic Pathway of the Ketogenic Diet.

Nevertheless, the effects of the KD on body fat, muscle mass, and exercise performance remain a topic of ongoing debate, with conflicting results reported in the literature. Therefore, this review examines the effects of the KD in areas where its potential benefits have been proposed and provides a brief overview of the evidence.

EFFECTS OF THE KETOGENIC DIET ON BODY FAT

Several studies have demonstrated the positive effects of the KD on body composition across various age groups and clinical conditions. For instance, a study comparing the KD with a hypocaloric diet in children and adolescents with obesity found that the KD was more effective in terms of weight loss and improvement in metabolic parameters. This study suggests that the KD can be a viable and safe alternative for weight loss in children and adolescents [8].

In another study conducted by Goss et al. [9], older adults with obesity maintained their calorie intake at normal levels over 8 weeks, and a comparison was made between the KD and a low-fat diet. The results indicated that the KD group exhibited a greater reduction in total fat mass than the low-fat diet group. Notably, the KD group experienced a threefold greater decrease in visceral adipose tissue. Consequently, this study suggests that weight loss through the KD, particularly in reducing visceral adipose tissue, which is strongly associated with metabolic and functional outcomes, may offer greater benefits for older adults than weight loss through a low-fat diet.

Hussain et al. [10], compared the effects of a 24-week low-calorie diet and the KD in individuals with type 2 diabetes. The KD was more effective than the low-calorie diet in significantly reducing body weight, body mass index (BMI), and waist circumference (WC). Additionally, the KD group demonstrated favorable effects on blood glucose levels and alterations in hemoglobin and glycosylated hemoglobin, total cholesterol, low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), and triglyceride (TG) levels. Some participants also experienced a 50% reduction or discontinuation of their initial dosage of antidiabetic medication.

Evidence regarding the effects of the KD on weight management is compelling; however, the underlying mechanisms of its action remain unclear. Paoli et al. [2], based on existing studies, presented evidence for the effectiveness of Initial decrease in TEE, followed by a significant increase after adaptation period the KD in weight loss as follows: 1) suppression of appetite through the satiety effect of protein and resulting changes the appetite hormone ghrelin levels, 2) reduced lipogenesis and increased fat oxidation, 3) enhanced metabolic efficiency in fat metabolism due to a decreased respiratory quotient, and 4) increased energy expenditure due to the thermic effect of protein and gluconeogenesis.

Regarding the fourth piece of evidence, Ludwig et al. [11] analyzed the impact of the KD on total energy expenditure (TEE). They investigated the differences in effects based on the duration of application. A meta-analysis of 29 studies, found that the KD initially leads to a temporary decrease in TEE; however, after approximately 2.5 weeks, a more significant increase in TEE was observed. During this adaptation period, individuals may experience symptoms of “Keto Flu,” including headaches, brain fog, fatigue, irritability, nausea, sleep disturbances, and constipation. This study provides partial insights into the mechanisms through which the KD promotes weight loss and the minimum adaptation period required to achieve the effects of the KD.

Available evidence suggests that the KD potentially exerts a favorable influence on body fat reduction [12,13]. Nevertheless, it remains imperative to meticulously consider individual variability in the response and long-term effects on body fat. From a long-term perspective, the success of a nutritional approach is determined by the extent of weight regain [14]. In this regard, there are limited data on the effect of the KD on weight loss or reduction in body fat [15,16].

Table 1.

The key aspects and findings of the references.

Diet and exercise play vital roles in reducing overweight status. High-intensity interval training (HIIT) has gained popularity as an efficient exercise strategy for improving cardiovascular endurance, enhancing heart metabolism, and positively affecting body composition changes [17-19]. Cipryan et al. [20] investigated the independent and interactive effects of the KD and HIIT on visceral fat reduction. The KD and KD+HIIT groups showed significant decreases in visceral fat, whereas the HIIT group showed minimal effects. Based solely on these findings, it can be concluded that the KD may be more effective for reducing visceral fat than HIIT alone without dietary intervention.

However, it is important to consider that this comparison focuses solely on changes in visceral fat and excludes other potential benefits of HIIT, such as cardiorespiratory fitness and cardiovascular health improvements. Nonetheless, the KD appears to be more effective in reducing visceral and overall body fat than exercise alone without dietary intervention. This is a potentially beneficial approach, particularly for individuals with limited engagement in physical activity.

EFFECTS OF THE KETOGENIC DIET ON MUSCLE MASS

As described in the preceding section, the KD is an effective strategy to reduce body weight and body fat. Another important aspect to consider is the potential effect of the KD on muscle mass. If the KD leads to a reduction in muscle mass and body fat, its applicability is limited for athletes and the general population.

Several studies have suggested that carbohydrate restriction in the KD may contribute to reduced muscle mass. The potential mechanisms through which the KD could negatively affect muscle mass are elucidated based on relevant literature as follows: 1) reduction in glycogen storage, which could impact muscle performance and recovery [21]; 2) inadequate intake of essential proteins crucial for muscle composition, maintenance, and recovery [22,23]; 3) changes in muscle energy availability because of the shift towards fat metabolism [24]; 4) impaired protein synthesis attributed to decreased insulin levels [15].

Interestingly, the combination of the KD and exercise did not prevent a reduction in muscle mass [9,25]. Some studies have indicated that during the period of KD application, exercise leads to increased utilization of muscle amino acids for gluconeogenesis due to glycogen depletion in the liver and muscles. This utilization could also be attributed to sodium and water excretion and body water loss due to glycogen depletion [9]. However, Cipryan et al. [20] pointed out that during the initial 4 weeks of the 12-week KD experimental period, there was a noticeable decline in participants’ muscle mass, which subsequently stabilized. They explained this as a transient phenomenon resulting from the initial reduction in total energy intake and changes in the carbohydrate proportion during the early stages of the KD intervention.

Conversely, numerous studies positively evaluate the KD’s impact on muscle mass. The proposed mechanisms are as follows: 1) muscle protein synthesis stimulation through activation of the mammalian target of rapamycin pathway [26]; 2) muscle protein breakdown reduction by suppressing the ubiquitin-proteasome system [27]; 3) increased secretion of growth hormone that plays a vital role in muscle growth and repair, promoting protein synthesis and inhibiting protein breakdown [28]; 4) nutrient uptake acceleration into muscle cells because of improved insulin sensitivity [29,30]; 5) promotion of muscle recovery, repair and growth through anti-inflammatory effects [31,32]; and glycogen preservation within muscles owing to increased fat oxidation.

Wilson et al. [33] compared the KD and a conventional diet over 11 weeks and found that both groups showed similar levels of muscle hypertrophy and increased strength. One noteworthy aspect of this study was that the participants were experienced in resistance training, and the KD group showed a remarkable increase in testosterone, a key factor in muscle synthesis, compared with the conventional diet group. Nonetheless, the current research results suggest that it is more appropriate to view the KD as a strategy for selectively removing fat without muscle loss rather than a strategy for muscle hypertrophy.

Table 2.

The key aspects and findings of the references.

The impact of the KD on muscle mass is still under discussion; however, it is believed to be influenced by key factors such as total energy and protein intake. To maximize muscle hypertrophy through the KD, daily total energy intake needs to be optimized. For maximal muscle hypertrophy, a caloric surplus is recommended, meaning that the daily total energy intake should exceed the total daily energy expenditure [34,35]. Consuming 15% more calories than the total daily energy expenditure is advised 36 . During periods of muscle hypertrophy, minimizing unnecessary fat gain by not exceeding a weekly weight gain of 0.25-0.5% of one’s body weight is essential [37]. Furthermore, excessive protein intake can induce gluconeogenesis and disrupt the state of ketosis, so protein consumption should be optimized. Consuming up to 2.1g/kg/day of protein allows for the maintaining a state of ketosis [38].

EFFECTS OF THE KETOGENIC DIET ON EXERCISE PERFORMANCE

Research related to the KD has primarily been conducted in the context of weight or fat reduction. Investigations into the relationship between the KD and exercise performance are lacking. The KD may positively impact exercise performance by providing benefits related to metabolic regulation, ketone body production, mitochondrial function enhancement, inflammation reduction, and weight loss [13,31,39,40]. The benefits of the KD in relation to exercise performance have been explored primarily in the context of endurance performance. Nonetheless, conflicting results exist in the data, and more studies have report that the KD provides no benefits or even impairs performance in athletes.

A study by Burke et al. [41] involved elite world-class race walkers who alternated between a typical high-carbohydrate diet and the KD for 3 weeks each while undergoing intensified training. This study observed significant improvements in peak aerobic capacity and whole-body fat oxidation at various speeds and intensities when following the KD However, this study highlights that the KD impacted exercise economy during the real-life race performance of elite endurance athletes. In other words, after adopting the KD, race walkers required increased oxygen consumption to maintain the same exercise workload or speed, indicating reduced efficiency. This reduction in the exercise economy ultimately negated the benefits of intensified training. Therefore, if exercise economy is impaired owing to the KD, it becomes challenging for race walkers to expect improvements in their performance.

Pathak and Baar [42] explained the decrease in high-intensity exercise performance due to the KD. The key muscle adaptation resulting from the KD and the activation of peroxisome proliferator-activated receptor (PPAR) enhances muscle fat oxidation but can also contribute to a reduction in high-intensity exercise performance. When PPAR is activated, it promotes the expression of genes related to fat oxidation and energy production. While this adaptation can benefit endurance activities requiring sustained energy over longer durations, it is less efficient at intensities greater than 65% of VO2max [43]. Endurance athletes on a KD ultimately require more oxygen to maintain the same exercise workload or speed as athletes on a conventional diet during high-intensity performance. This PPAR-driven shift in energy substrate utilization may lead to reduced performance during demanding endurance activities that require intense energy bursts.

Furthermore, there have been concerns about the potential health risks associated with athletes adopting the KD. One such study by Volek et al. [39] investigated the metabolic characteristics of 10 long-distance runners who followed a KD for over 6 months. The results indicated that runners experienced decreased body weight and body fat compared with their pre-KD state. However, the blood concentration of ketone bodies, a metabolic byproduct, significantly increased, leading to side effects such as fatigue, insomnia, and digestive issues in athletes. These findings suggest that adopting an extremely low-carbohydrate high-fat diet, such as the KD, may pose potential health risks to individuals engaged in long-distance exercise.

In contrast, some studies have reported improvements in high-intensity endurance performance. McSwiney et al. [44] investigated the KD in endurance athletes over 12 weeks and conducted various performance tests, including a 100 km timed trial, a 6-second sprint, and a critical power test. The results showed that compared with athletes following a conventional diet, there was no significant difference in the 100 km timed trial performance after adapting to the KD. However, the KD-adapted athletes consistently demonstrated increased fat oxidation rates during exercise. In the 6-second sprint conducted immediately after the 100 km timed trial to simulate the sprint finish in endurance races and the critical power test, athletes following the KD exhibited improved performance.

Although there is insufficient information available on the effects of the KD on anaerobic exercise, studies have suggested that the KD may have a negative impact on anaerobic exercise. These negative effects include the following: 1) impaired ability for glycolysis, which is necessary for short-term high-intensity anaerobic exercise [24,39]; 2) limitation in glycogen utilization leading to early fatigue and reduced performance during exercise [41]; 3) limited availability of creatine phosphate regeneration, which impacts the rate of ATP regeneration required for explosive exercise [26,39]; 4) decreased glycogen and insulin secretion leading to increased protein breakdown resulting in muscle mass reduction [9,30]; 5) electrolyte loss and dehydration due to reduced carbohydrate intake resulting in muscle cramps, reduced muscle function, and impaired performance during anaerobic activities [24,44].

Nevertheless, a study by Paoli et al. [45] targeted elite gymnasts and implemented the KD for 1 month without altering their training routines. The results revealed a reduction in body fat and maintenance of strength. Furthermore, Kephart et al. [46] analyzed the impact of the KD over 3 months on exercise performance and body composition in CrossFit trainees. No significant differences in strength or muscle mass between the KD and control groups were observed. Similarly, Sawyer et al. [47], focused on men and women who strength-trained and investigated the effects of a 7-day short-term KD on strength and power. The findings indicated that despite reductions in body weight, both sexes sustained strength and power. This provides a rationale for the KD in the domains of strength and power.

Despite the ongoing debate surrounding the impact of the KD on exercise performance, it appears that the KD can be particularly beneficial for athletes involved in weight-category sports and those in whom aesthetic appearance plays a crucial role in their performance. The KD has the potential to preserve muscle mass regardless of the type of exercise and supports the reduction of body fat [48], making it a robust approach.

Paoli et al. [49] focused on natural bodybuilders over 8 weeks with equal total energy and protein intake conditions: one group followed the KD, whereas the other adhered to a conventional diet. The results indicated that the KD group significantly reduced body fat more than the conventional diet group. The conventional diet group showed a slight increase in muscle mass, whereas the KD group maintained their existing muscle mass without experiencing muscle loss. Moreover, insulin sensitivity, a critical metabolic health marker, significantly improved only in the KD group. On the other hand, inflammatory cytokines (IL-1, IL-6, TNF-a) increased in the conventional diet group but decreased in the KD group compared with baseline. Therefore, implementing the KD during a phase focused on maximizing fat reduction can serve as a strategy not only for efficient fat loss without muscle loss but also for preventing potential metabolic and immune health decline during the body fat reduction phase. For these reasons, the KD can provide advantages to athletes with weight category restrictions and individuals aiming to reduce fat while preserving muscle mass.

The potential of the KD to improve exercise performance remains a topic of debate. In summary, the KD can enhance endurance performance by boosting fat oxidation; however, it may lead to a performance decline in high-intensity activities that rely heavily on glycogen. To effectively utilize the KD to enhance exercise performance, it is crucial to consider factors such as individual characteristics, duration of dietary adaptation, training level, and the type of exercises performed.

Table 3.

The key aspects and findings of the references.

CONCLUSION

The KD, which restricts carbohydrate intake and emphasizes the consumption of fat and proteins, can potentially affect body fat, muscle mass, and exercise performance by altering the body’s energy supply and metabolic processes. Although scientific evidence has not yet been fully established and academic consensus has not been reached, this review provides an overview of the research on the effects of the KD on these parameters. When considering the available research, it is important to note that the long-term effects and safety of the KD have not been sufficiently established. However, in the short-term, the KD has been proven to be an effective method for reducing body fat and maintaining muscle mass. The impact of KD on exercise performance varies and depends on individual factors, adaptation duration, training status, and the specific type of exercise performed. Therefore, drawing definitive conclusions from existing data is challenging. Future research should prioritize optimizing the application of the KD in diverse populations, elucidating its underlying mechanisms, and validating its long-term effects on sustainability and safety.

References

1. Maffetone PB, Laursen PB. Revisiting the global overfat pandemic. Front Public Heal 2020;8:51.

2. Paoli A. Ketogenic diet for obesity: friend or foe? Int J Environ Res Public Health 2014;11:2092–107.

3. Streijger F, Plunet WT, Lee JHT, Liu J, Lam CK, Park S, Hilton BJ, Fransen BL, Matheson KAJ, Assinck P, Kwon PK, Tetzlaff W. Ketogenic diet improves forelimb motor function after spinal cord injury in rodents. PLoS One 2013;8e78765.

4. Bostock ECS, Kirkby KC, Taylor BV, Hawrelak JA. Consumer reports of “keto flu” associated with the ketogenic diet. Front Nutr 2020;7:20.

5. Noto H, Goto A, Tsujimoto T, Noda M. Low-carbohydrate diets and all-cause mortality: a systematic review and meta-analysis of observational studies. PLoS One 2013;8e55030.

6. Nymo S, Coutinho SR, Jorgensen J, Rehfeld JF, Truby H, Kulseng B, Martins C. Timeline of changes in appetite during weight loss with a ketogenic diet. Int J Obes (Lond) 2017;41:1224–31.

7. Badman MK, Kennedy AR, Adams AC, Pissios P, Maratos-Flier E. Very low carbohydrate ketogenic diet improves glucose tolerance in ob/ob mice independently of weight loss. Am J Physiol Endocrinol Metab 2009;297:E1197–204.

8. Partsalaki I, Karvela A, Spiliotis BE. Metabolic impact of a ketogenic diet compared to a hypocaloric diet in obese children and adolescents. J Pediatr Endocrinol Metab 2012;25:697–704.

9. Goss AM, Gower B, Soleymani T, Stewart M, Pendergrass M, Lockhart M, Krantz O, Dowla S, Bush N, Barry VG, Fontaine KR. Effects of weight loss during a very low carbohydrate diet on specific adipose tissue depots and insulin sensitivity in older adults with obesity: a randomized clinical trial. Nutr Metab (Lond) 2020;17:64.

10. Hussain TA, Mathew TC, Dashti AA, Asfar S, Al-Zaid N, Dashti HM. Effect of low-calorie versus low-carbohydrate ketogenic diet in type 2 diabetes. Nutrition 2012;28:1016–21.

11. Ludwig DS, Dickinson SL, Henschel B, Ebbeling CB, Allison DB. Do lower-carbohydrate diets increase total energy expenditure? An updated and reanalyzed meta-analysis of 29 controlled-feeding studies. J Nutr 2021;151:482–90.

12. Gibson AA, Seimon RV, Lee CMY, Ayre J, Franklin J, Markovic TP, Caterson ID, Sainsbury A. Do ketogenic diets really suppress appetite? A systematic review and meta-analysis. Obes Rev 2015;16:64–76.

13. Sackner-Bernstein J, Kanter D, Kaul S. Dietary intervention for overweight and obese adults: comparison of low-carbohydrate and low-fat diets. A meta-analysis. PLoS One 2015;10e0139817.

14. Janda M, Zeidler D, Bohm G, Schoberberger R. An instrument to measure adherence to weight loss programs: the compliance praxis survey-diet (COMPASS-diet). Nutrients 2013;5:3828–38.

15. Sumithran P, Prendergast LA, Delbridge E, Purcell K, Shulkes A, Kriketos A, Proietto J. Ketosis and appetite-mediating nutrients and hormones after weight loss. Eur J Clin Nutr 2013;67:759–64.

16. Paoli A, Bianco A, Grimaldi KA, Lodi A, Bosco G. Long term successful weight loss with a combination biphasic ketogenic mediterranean diet and mediterranean diet maintenance protocol. Nutrients 2013;5:5205–17.

17. Gillen JB, Martin BJ, MacInnis MJ, Skelly LE, Tarnopolsky MA, Gibala MJ. Twelve weeks of sprint interval training improves indices of cardiometabolic health similar to traditional endurance training despite a five-fold lower exercise volume and time commitment. PLoS One 2016;11e0154075.

18. Sawyer BJ, Tucker WJ, Bhammar DM, Ryder JR, Sweazea KL, Gaesser GA. Effects of high-intensity interval training and moderate-intensity continuous training on endothelial function and cardiometabolic risk markers in obese adults. J Appl Physiol 2016;121:279–88.

19. Ramos JS, Dalleck LC, Tjonna AE, Beetham KS, Coombes JS. The impact of high-intensity interval training versus moderate-intensity continuous training on vascular function: a systematic review and meta-analysis. Sports Med 2015;45:679–92.

20. Cipryan L, Dostal T, Litschmannova M, Hofmann P, Maffetone PB, Laursen PB. Effects of a very low-carbohydrate high-fat diet and high-intensity interval training on visceral fat deposition and cardiorespiratory fitness in overfat individuals: a randomized controlled clinical trial. Front Nutr 2021;8:785694.

21. Cahill GF. Fuel metabolism in starvation. Annu Rev Nutr 2006;26:1–22.

22. Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378:826–37.

23. Tinsley GM, Willoughby DS. Fat-free mass changes during ketogenic diets and the potential role of resistance training. Int J Sport Nutr Exerc Metab 2016;26:78–92.

24. Paoli A, Mancin L, Bianco A, Thomas E, Mota JF, Piccini F. Ketogenic diet and microbiota: friends or enemies? Genes (Basel) 2019;10:534.

25. Greene DA, Varley BJ, Hartwig TB, Chapman P, Rigney M. A low-carbohydrate ketogenic diet reduces body weight without compromising performance in powerlifting and olympic weightlifting athletes. J Strength Cond Res 2018;32:3373–82.

26. Gasior M, Rogawski MA, Hartman AL. Neuroprotective and disease-modifying effects of the ketogenic diet. Behav Pharmacol 2006;17:431–9.

27. Tisdale MJ. Mechanisms of cancer cachexia. Physiol Rev 2009;89:381–410.

28. Poplawski MM, Mastaitis JW, Isoda F, Grosjean F, Zheng F, Mobbs CV. Reversal of diabetic nephropathy by a ketogenic diet. PLoS One 2011;6e18604.

29. de Metz J, Ackermans MT, Endert E, Pijl H, Kuipers F, Meijer AJ, Sauerwein HP, Romijn JA. Dietary fat content alters insulin-mediated glucose metabolism in healthy men. Am J Clin Nutr 2001;73:554–9.

30. Sondike SB, Coppermann N, Jacobson MS. Effects of a low-carbohydrate diet on weight loss and cardiovascular risk factor in overweight adolescents. J Pediatr 2003;142:253–8.

31. Youm YH, Nguyen KY, Grant RW, Goldberg EL, Bodogai M, Kim D, D’Agostino D, Planavsky N, Lupfer C, Kanneganti TD, Kang S, Horvath TL, Fahmy TK, Crawford PA, Biragyn A, Alnemri E, Dixit VD. The ketone metabolite β-hydroxybutyrate blocks NLRP3 inflammasome-mediated inflammatory disease. Nat Med 2015;21:263–9.

32. Maalouf M, Rho JM, Mattson MP. The neuroprotective properties of calorie restriction, the ketogenic diet, and ketone bodies. Brain Res Rev 2009;59:293–315.

33. Wilson JM, Lowery RP, Roberts MD, Sharp MH, Joy JM, Shields KA, Partl JM, Volek JS, D’Agostino DP. Effects of ketogenic dieting on body composition, strength, power, and hormonal profiles in resistance training men. J Strength Cond Res 2020;34:3463–74.

34. Slater GJ, Dieter BP, Marsh DJ, Helms ER, Shaw G, Iraki J. Is an energy surplus required to maximize skeletal muscle hypertrophy associated with resistance training. Front Nutr 2019;6:131.

35. Vargas-Molina S, Gómez-Urquiza LJ, Benítez-Porres J. Effects of the ketogenic diet on muscle hypertrophy in resistance-trained men and women: a systematic review and meta-analysis. Int J Environ Res Public Health 2022;19:12629.

36. Lambert CP, Frank LL, Evans WJ. Macronutrient considerations for the sport of bodybuilding. Sports Med 2004;34:317–27.

37. Iraki J, Fitschen P, Espinar S, Helm E. Nutrition recommendations for bodybuilders in the off-season: a narrative review. Sports (Basel) 2019;7:154.

38. Paoli A, Bianco A, Grimaldi KA. The ketogenic diet and sport: a possible marriage? Exerc Sport Sci Rev 2015;43:153–62.

39. Volek JS, Freidenreich DJ, Saenz C, Kunces LJ, Creighton BC, Bartley JM, Davitt PM, Munoz CX, Anderson JM, Maresh CM, Lee EC, Schuenke MD, Aerni G, Kraemer WJ, Phinney SD. Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism 2016;65:100–10.

40. Newman JC, Verdin E. β-hydroxybutyrate: a signaling metabolite. Annu Rev Nutr 2017;37:51–76.

41. Burke LM, Ross ML, Garvican-Lewis LA, Welvaert M, Heikura IA, Forbes SG, Mirtschin JG, Cato LE, Strobel N, Sharma AP, Hawley JA. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. J Physiol 2017;595:2785–807.

42. Pathak SJ, Baar K. Ketogenic diets and mitochondrial function: benefits for aging but not for athletes. Exerc Sport Sci Rev 2023;51:27–33.

43. Shaw DM, Merien F, Braakhuis A, Maunder ED, Dulson DK. Effect of a ketogenic diet on submaximal exercise capacity and efficiency in runners. Med Sci Sports Exerc 2019;51:2135–46.

44. McSwiney FT, Wardrop B, Hyde P N, Lafountain R A, Volek JS, Doyle L. Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes. Metabolism 2018;83:e1–2.

45. Paoli A, Grimaldi K, D’Agostino D, Cenci L, Bianco A, Palma A. Ketogenic diet does not affect strength performance in elite artistic gymnasts. J Int Soc Sports Nutr 2012;9:34.

46. Kephart WC, Pledge CD, Roberson PA, Mumford PW, Romero MA, Mobley CB, Young KC, Lowery RP, Wilson JM, Huggins KW, Roberts MD. The three-month effects of a ketogenic diet on body composition, blood parameters, and performance metrics in crossfit trainees: a pilot study. Sports (Basel) 2018;6:1.

47. Sawyer JC, Wood RJ, Davidson PW, Collins SM, Matthews TD, Gregory SM, Paolone VJ. Effects of a short-term carbohydrate-restricted diet on strength and power performance. J Strength Cond Res 2013;27:2255–62.

48. Yancy WS Jr, Olsen MK, Guyton JR, Westman EC. A low-carbohydrate, ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia: a randomized, controlled trial. Ann Intern Med 2004;140:769–77.

49. Paoli A, Cenci L, Pompei P, Sahin N, Bianco A, Neri M, Caprio M, Moro T. Effects of two months of very low carbohydrate ketogenic diet on body composition, muscle strength, muscle area, and blood parameters in competitive natural body builders. Nutrients 2021;13:374.

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Population/Participants	Intervention	Key Findings	References
Obese children and adolescents	KD vs. hypocaloric diet	KD effective for weight loss and metabolic improvements	[8]
Obese older adults	KD vs. low-fat diet	Greater reduction in total fat mass and visceral fat in KD Group	[9]
Individuals with type 2 diabetes	KD vs. low-calorie diet	KD’s effectiveness in reducing body weight, BMI, waist circumference, and favorable effects on blood glucose and lipid levels	[10]
29 Controlled-Feeding Studies	Impact of KD on Total Energy Expenditure: Meta-Analysis	Initial decrease in TEE, followed by a significant increase after adaptation period	[11]
Investigation of KD and HIIT	KD vs. KD+HIIT vs. HIIT alone	KD more effective than HIIT alone in reducing visceral fat	[20]

Population/Participants	Intervention	Key Findings	References
Obese adults	HIIT vs VLCHF vs VLCHF+HIIT for 12 week	The KD group experienced a reduction in muscle mass during the initial 4 weeks, but it stabilized thereafter. HIIT could not prevent the muscle loss associated with the ketogenic diet.	[20]
Elite level powerlifters and Olympic weightlifters	KD vs. conventional diet 6 months (each for 3 months in a crossover design)	The KD phase resulted lower lean mass compared with the conventional diet phase.	[25]
Resistance-Trained Men	KD vs. conventional diet over an 11-week	Similar levels of muscle hypertrophy and strength, increase testosterone	[33]
Resistance-Trained Men and Women	Effects of the Ketogenic Diet on Muscle Hypertrophy: A Systematic Review and Meta-Analysis	Applying a KD without energy restriction can increase FFM.	[35]

Population/Participants	Intervention	Key Findings	References
Elite race walkers	High carbohydrate vs. KD diets during intensified training	Improved peak aerobic capacity and fat oxidation during KD but reduced exercise economy during real-life race performance	[41]
Elite runner	Explains KD’s impact on high- intensity exercise performance	Submaximal exercise performance (<60% V˙O2max) may improve in runners, but at high exercise intensities (approximately >65% V˙ O2max), the efficient transport of fatty acids to the mitochondria is limited, resulting in a negative impact on performance.	[42]
Endurance athletes	KD applied for 12 weeks to endurance athletes in various performance tests.	No significant difference in a 100km time trial performance, but KD-adapted athletes consistently exhibited higher fat oxidation rates and improved performance in high-intensity sprint and critical power tests.	[44]
Long-distance runners	Investigated long-distance runners following KD for over six months.	Runners experienced decreased body weight and fat but had increased ketone body levels, leading to side effects such as fatigue, insomnia, and digestive issues.	[39]
Elite artistic gymnasts, crossfit trainees, trained men	KD’s effects on strength and power performance	Maintenance of strength and power performance	[45], [46], [47]
Natural Body Builder	Investigated long-distance runners following KD for over 8 weeks	Significant reduction in body fat while maintaining muscle mass and decreased inflammatory cytokines	[48]