madman
Super Moderator
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
Abstract
Background: Ketogenic diet (KD) is a nutritional approach that restricts daily carbohydrates, replacing most of the reduced energy with fat, while maintaining an adequate quantity of protein. Despite the widespread use of KD in weight loss in athletes, there are still many concerns about its use in sports requiring muscle mass accrual. Thus, the present study sought to investigate the influence of a KD in competitive natural bodybuilders.
Methods: Nineteen volunteers (27.4 ± 10.5 years) were randomly assigned to a ketogenic diet (KD) or to a western diet (WD). Body composition, muscle strength, and basal metabolic rate were measured before and after two months of intervention. Standard blood biochemistry, testosterone, IGF-1, brain-derived neurotrophic factor (BDNF), and inflammatory cytokines (IL6, IL1β, TNFα) were also measured.
Results: Body fat significantly decreased in KD (p = 0.030); whilst lean mass increased significantly only in WD (p < 0.001). Maximal strength increased similarly in both groups. KD showed a significant decrease in blood triglycerides (p < 0.001), glucose (p = 0.001), insulin (p < 0.001) and inflammatory cytokines compared to WD whilst BDNF increased in both groups with significantly greater changes in KD (p < 0.001).
Conclusions: KD may be used during bodybuilding preparation for health and learning purposes but with the caution that hypertrophic muscle response could be blunted.
1. Introduction
A ketogenic diet (KD) is a nutritional approach based on a reduced intake of carbohydrates (less than 20/30 g per day or 5% of total energy) [1–3], a high-fat content, and an adequate level of proteins, the latter generally close to or slightly higher than the Italian recommended daily intake (LARNs recommendation) of 0.9 g per kg of body weight [4]. The metabolic advantage induced by KD is represented by the drastic reduction in carbohydrates, which forces the body to primarily use fat as a fuel source as demonstrated by the decrease of the respiratory exchange ratio (RER) [5,6].
Glucose is a fundamental energy source for the central nervous system, which is protected by the blood-brain barrier not allowing the passage of free fatty acids. After a few days of KD, there is a drop in glucose availability due to reduced glycogen stores and thus an alternative energy source is required [7,8]. This energy is supplied by ketone bodies (KBs): acetoacetate (AcAc), 3-hydroxybutyrate (BHB), and acetone. KBs are generated through a process called ketogenesis from acetyl-CoA that occurs mainly in the mitochondrial matrix of the liver. Although created in the liver, this organ is unable to utilize KB due to a lack of the succinyl-CoA: 3-CoA transferase enzyme, which is required to convert acetoacetate to aceto-acetyl-CoA. KBs are thus released into the extrahepatic bloodstream and can be used by other tissues as an energy source, by converting BHB into acetoacetate and then into aceto-acetyl-CoA, which can be further transformed into two acetyl-CoA molecules and enter the Krebs cycle [9]. At the end of this process, the energy produced from KBs is greater compared with glucose [2,10]. Initially, the necessary amount of acetyl-CoA is supplied by hepatic glycogenolysis and gluconeogenesis, but after four-seven days of KD, lipolysis of adipose tissue becomes the main source. In the long term, this adaptation translates into a reduction in the respiratory ratio which represents the metabolic switch towards a greater reliance on fatty acids [6,11].
KD is a well-proven approach to promote weight loss [2], and it has recently been used as a valuable therapeutic option to treat metabolic disorders, cardiovascular disease, and type 2 diabetes [12]. Its role in sports performance is still controversial, with some authors experiencing favorable effects [3,13] whilst others discourage the use of such a dietetic approach, at least in endurance sports [14–16].
For athletes who compete in weight-category sports, KD could be a safe weight-loss method, not compromising performance, therefore it may represent a legitimate and important tool for athletes. Paoli et al., for instance, demonstrated that 30 days of KD decreased body weight and body fat without negative effects on strength in high-level gymnasts [13]. However, it might seem counterproductive for those athletes who seek maximum muscle hypertrophy [17], as several studies have shown no accretion of muscle mass during the ketosis phase [13,18–20].
Despite this, numerous bodybuilders use KD without a justified reason; however, no studies have yet explored its role in this particular sport category [21–23]. Professional bodybuilders’ goals are to keep a perfect balance between muscle size and body fat, in order to obtain the most accurate symmetry and muscular proportion. To achieve their objectives, bodybuilders undergo a cycle of different training intensities in combination with the various dietetic regimen in order to increase muscle mass during the “off-season” and reduce fat mass during competition preparation [21]. In this context, KD seems to be a useful diet to reduce fat mass, but its role in preserving athletic performance and muscle hypertrophy in physique athletes is still poorly investigated.
The high intensity and frequency of training employed by bodybuilders during their contest preparation may also induce muscle damage [24–26], which could ultimately result in a chronic inflammatory status, with an increased level of IL-6, IL-1, and TNF-α [27]. On the other hand, a weight loss program can increase stress, anxiety and negatively affect an athlete’s mood [28]. The brain-derived neurotrophic factor (BDNF) is a protein associated with major depressive disorders and stress situations [29,30]. It has been shown that KD may have positive effects on inflammation [31–33] and can reduce depression-like behaviors [34] in both animals and human models, but no data are available about its effect on athletes such as bodybuilders
The aim of the present study is to evaluate the effects of the ketogenic diet on the body composition, muscle mass, strength, and some blood parameters mainly related to lipid profile, hormonal (i.e., IGF-1), and inflammatory status (i.e., IL-6, TNFα, and IL-1β) in competitive bodybuilding athletes. Basal metabolism and respiratory quotient were also assessed in order to monitor the metabolic adaptation to KD.
6. Conclusions
The results show that a KD diet may represent an adequate dietary approach for BB athletes. Despite the lack of hypertrophic response in the KD group, muscle mass was maintained, a phenomenon that often does not occur during low-calorie diets. Similarly, although the time of year was not the one that athletes usually dedicate to training for fat loss (“cutting”), KD proved to be a good strategy to reduce body fat.
KD also resulted in a decrease in inflammatory cytokines and the increase in BDNF, suggesting that KD can be a valid tool for dealing with moments (such as that of “weightlifting”) where stress management and maintenance of motivation are hard to handle. KD is not a regime to be followed lightly and independently but requires the presence of a professional; in these circumstances, KD represents a fundamental tool in the nutritionist’s baggage to face various conditions and needs, including those of sports.
Abstract
Background: Ketogenic diet (KD) is a nutritional approach that restricts daily carbohydrates, replacing most of the reduced energy with fat, while maintaining an adequate quantity of protein. Despite the widespread use of KD in weight loss in athletes, there are still many concerns about its use in sports requiring muscle mass accrual. Thus, the present study sought to investigate the influence of a KD in competitive natural bodybuilders.
Methods: Nineteen volunteers (27.4 ± 10.5 years) were randomly assigned to a ketogenic diet (KD) or to a western diet (WD). Body composition, muscle strength, and basal metabolic rate were measured before and after two months of intervention. Standard blood biochemistry, testosterone, IGF-1, brain-derived neurotrophic factor (BDNF), and inflammatory cytokines (IL6, IL1β, TNFα) were also measured.
Results: Body fat significantly decreased in KD (p = 0.030); whilst lean mass increased significantly only in WD (p < 0.001). Maximal strength increased similarly in both groups. KD showed a significant decrease in blood triglycerides (p < 0.001), glucose (p = 0.001), insulin (p < 0.001) and inflammatory cytokines compared to WD whilst BDNF increased in both groups with significantly greater changes in KD (p < 0.001).
Conclusions: KD may be used during bodybuilding preparation for health and learning purposes but with the caution that hypertrophic muscle response could be blunted.
1. Introduction
A ketogenic diet (KD) is a nutritional approach based on a reduced intake of carbohydrates (less than 20/30 g per day or 5% of total energy) [1–3], a high-fat content, and an adequate level of proteins, the latter generally close to or slightly higher than the Italian recommended daily intake (LARNs recommendation) of 0.9 g per kg of body weight [4]. The metabolic advantage induced by KD is represented by the drastic reduction in carbohydrates, which forces the body to primarily use fat as a fuel source as demonstrated by the decrease of the respiratory exchange ratio (RER) [5,6].
Glucose is a fundamental energy source for the central nervous system, which is protected by the blood-brain barrier not allowing the passage of free fatty acids. After a few days of KD, there is a drop in glucose availability due to reduced glycogen stores and thus an alternative energy source is required [7,8]. This energy is supplied by ketone bodies (KBs): acetoacetate (AcAc), 3-hydroxybutyrate (BHB), and acetone. KBs are generated through a process called ketogenesis from acetyl-CoA that occurs mainly in the mitochondrial matrix of the liver. Although created in the liver, this organ is unable to utilize KB due to a lack of the succinyl-CoA: 3-CoA transferase enzyme, which is required to convert acetoacetate to aceto-acetyl-CoA. KBs are thus released into the extrahepatic bloodstream and can be used by other tissues as an energy source, by converting BHB into acetoacetate and then into aceto-acetyl-CoA, which can be further transformed into two acetyl-CoA molecules and enter the Krebs cycle [9]. At the end of this process, the energy produced from KBs is greater compared with glucose [2,10]. Initially, the necessary amount of acetyl-CoA is supplied by hepatic glycogenolysis and gluconeogenesis, but after four-seven days of KD, lipolysis of adipose tissue becomes the main source. In the long term, this adaptation translates into a reduction in the respiratory ratio which represents the metabolic switch towards a greater reliance on fatty acids [6,11].
KD is a well-proven approach to promote weight loss [2], and it has recently been used as a valuable therapeutic option to treat metabolic disorders, cardiovascular disease, and type 2 diabetes [12]. Its role in sports performance is still controversial, with some authors experiencing favorable effects [3,13] whilst others discourage the use of such a dietetic approach, at least in endurance sports [14–16].
For athletes who compete in weight-category sports, KD could be a safe weight-loss method, not compromising performance, therefore it may represent a legitimate and important tool for athletes. Paoli et al., for instance, demonstrated that 30 days of KD decreased body weight and body fat without negative effects on strength in high-level gymnasts [13]. However, it might seem counterproductive for those athletes who seek maximum muscle hypertrophy [17], as several studies have shown no accretion of muscle mass during the ketosis phase [13,18–20].
Despite this, numerous bodybuilders use KD without a justified reason; however, no studies have yet explored its role in this particular sport category [21–23]. Professional bodybuilders’ goals are to keep a perfect balance between muscle size and body fat, in order to obtain the most accurate symmetry and muscular proportion. To achieve their objectives, bodybuilders undergo a cycle of different training intensities in combination with the various dietetic regimen in order to increase muscle mass during the “off-season” and reduce fat mass during competition preparation [21]. In this context, KD seems to be a useful diet to reduce fat mass, but its role in preserving athletic performance and muscle hypertrophy in physique athletes is still poorly investigated.
The high intensity and frequency of training employed by bodybuilders during their contest preparation may also induce muscle damage [24–26], which could ultimately result in a chronic inflammatory status, with an increased level of IL-6, IL-1, and TNF-α [27]. On the other hand, a weight loss program can increase stress, anxiety and negatively affect an athlete’s mood [28]. The brain-derived neurotrophic factor (BDNF) is a protein associated with major depressive disorders and stress situations [29,30]. It has been shown that KD may have positive effects on inflammation [31–33] and can reduce depression-like behaviors [34] in both animals and human models, but no data are available about its effect on athletes such as bodybuilders
The aim of the present study is to evaluate the effects of the ketogenic diet on the body composition, muscle mass, strength, and some blood parameters mainly related to lipid profile, hormonal (i.e., IGF-1), and inflammatory status (i.e., IL-6, TNFα, and IL-1β) in competitive bodybuilding athletes. Basal metabolism and respiratory quotient were also assessed in order to monitor the metabolic adaptation to KD.
6. Conclusions
The results show that a KD diet may represent an adequate dietary approach for BB athletes. Despite the lack of hypertrophic response in the KD group, muscle mass was maintained, a phenomenon that often does not occur during low-calorie diets. Similarly, although the time of year was not the one that athletes usually dedicate to training for fat loss (“cutting”), KD proved to be a good strategy to reduce body fat.
KD also resulted in a decrease in inflammatory cytokines and the increase in BDNF, suggesting that KD can be a valid tool for dealing with moments (such as that of “weightlifting”) where stress management and maintenance of motivation are hard to handle. KD is not a regime to be followed lightly and independently but requires the presence of a professional; in these circumstances, KD represents a fundamental tool in the nutritionist’s baggage to face various conditions and needs, including those of sports.
