The Ketogenic Diet And Sport A Possible Marriage Pdf
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- Ketogenic Diet and Sport Performance
- Keto Diet Athletes - TRANSPARÊNCIA
- The Ketogenic Diet and Sport: A Possible Marriage?
- Effect of a four-week ketogenic diet on exercise metabolism in CrossFit-trained athletes
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Ketogenic Diet and Sport Performance
Metrics details. The ketogenic diet is becoming a popular nutritional model among athletes. However, the relationship between its use and metabolism during exercise seems to have not been fully investigated. During the ICT while consuming the customary diet and after the KD , oxygen uptake and carbon dioxide exhalation were registered, and CHO and fat utilization as well as energy expenditure were calculated.
Male CrossFit-trained athletes seem to be more prone to shifts in macronutrient utilization in favor of fat utilization during submaximal intensity exercise under a ketogenic diet than are female athletes. Registered 11 September retrospectively registered. Carbohydrates CHO and fat are the main sources of fuel oxidized in muscles during exercise [ 1 ]. In contrast to fat, endogenous stores of CHO are limited. However, there is a vast quantity of fat stored even in the leanest of athletes approximately , kJ [ 2 ].
Physical performance mainly endurance and exercise ability can be limited when endogenous CHO are the dominant fuel [ 3 ]. A high CHO diet has been traditionally promoted for athletes in order to maximize muscle and liver glycogen stores, as well as the ability to maintain their effective utilization, which often determines the final effectiveness of physical exercise [ 4 ].
These dietary regimes are supposed to optimize fuel mobilization and utilization during exercise by activating fatty acids as an energy source during exercise. After several days of drastically reduced CHO intake while maintaining the usual energy intake, glucose reserves become depleted and are no longer sufficient for either normal fat oxidation via oxaloacetate in the Krebs cycle or to supply energy to the brain and central nervous system [ 10 ].
It is worth mentioning that the first studies on KD focused mainly on its efficacy in treating epilepsy and came from the early s [ 12 ]. Its possible efficacy was further investigated with regard to weight loss [ 13 ], insulin resistance, diabetes or high blood pressure [ 14 ]. The KD can be characterized by pleiotropic activity. The significant influence of the KD may be related to its impact on the adaptation of the body through the regulation of the molecular mechanisms of cellular signaling [ 11 , 15 , 16 , 17 ].
Activation of these signaling pathways may lead to a significant increase in the physical and exercise capacity, by stimulating, e. Beneficial effects may also involve the strengthening of brain function and cognitive performance [ 18 , 20 , 31 ].
However, the main mechanism of influence of the KD on the human body is its impact on metabolic reorganization [ 11 , 16 , 32 , 33 , 34 , 35 ]. After transporting the KB to extrahepatic cells, they can be used as an energy substrate acetyl-CoA in the production of ATP through the oxidative phosphorylation pathway in the citric acid cycle TCA [ 16 ].
It can therefore be concluded that diets high in fat upregulate the release, transport, uptake, and utilization of fat in the muscle, even in endurance athletes whose training would have been expected to maximize such adaptations [ 39 , 40 , 41 ].
The effectiveness of KD in supporting weight reduction has made it quite popular among athletes competing in sport disciplines with weight categories or aesthetic aspects [ 42 , 43 ].
New lines of research concerning the utility of KD in sports have focused on performance in endurance trained athletes, most of which concurrently addressed the issue of energy metabolism during exercise and revealed increased fat oxidation under KD [ 3 , 41 , 44 , 45 , 46 ]. However, few studies have investigated the relations between exercise intensity as measured by maximal oxygen uptake and fat utilization in detail and these have been underpowered due to low sample sizes [ 46 ].
Moreover, no between-gender comparisons in possible energy metabolism differences related to the KD have been made. However, it is known that there are gender differences in whole-body fat oxidation kinetics during exercise.
Fat oxidation rates and maximal fat oxidation at submaximal intensities are greater in women than in men, and maximal fat oxidation occur at substantially higher exercise intensities in women than in men [ 47 ]. Based on the above facts, we hypothesized that in actively training male and female CrossFit practitioners, a KD for 4 weeks would induce shifts in fuel utilization during exercise in favor of fat utilization.
Thirty participants were initially enrolled in this study. We included both males and females because of the equal participation of both genders in CrossFit training, as well as because of the willingness to assess whether the KD has an impact related to the gender of the subjects undergoing this type of training.
For females, additional exclusion criteria were being pregnant or planning to become pregnant during the study or the presence of a menstrual cycle disorder. The primary recruitment strategy was contacting certified Crossfit trainers responsible for managing training sessions in Crossfit clubs located in the Wielkopolska region. They assisted with the identification, inclusion, and confirmation of the aspects declared by the participants related to the inclusion criteria such as training experience and number of sessions per week.
Written informed consent was obtained from all participants before the study began. All procedures were conducted in accordance with the ethical standards of the Helsinki Declaration. The trial was conducted from January to December The study was registered retrospectively since registration was not required when the study enrolment started. The authors confirm that all ongoing and related trials for this intervention are registered.
The study protocol included three visits to the laboratory Fig. The first visit T 0 consisted of familiarization to the progressive cycling test, food recording method, physical activity questionnaire and the study protocol for the physical capacity test as well as anthropometric measurements. During this period, total daily energy expenditure EE was estimated.
After the run-in phase, the first laboratory study visit was conducted T 1 during which an incremental cycling test was performed Fig.
On the next day, after the baseline T 1 testing, the subjects started the dietary intervention Fig. After the participants had completed a four-week experimental KD intervention, the second series of laboratory study visits T 2 was conducted. Exercise tests were performed twice, before at the CD and after the KD diet T 1—2 , in the laboratory. During the exercise tests, substrate oxidation rates and EE were evaluated. The subjects were asked to maintain a similar training load and the same physical activity level throughout the study.
At each visit, body mass and composition were measured, followed by performance of the exercise tests. Three hours before the T 1 and T 2 visits, the participants consumed a standardized meal corresponding to their habitual food intake or to menu of the KD diet, respectively.
The three-hour period between the meal and exercise was chosen to prevent potential short-term effects of a meal on exercise performance [ 48 , 49 , 50 ]. On the day following T 1 visit, the participants began their prescribed four-week KD diet ending with the T 2 visit. The KD model was individualized to ensure weight maintenance throughout the dietary interventions and diets were energetically normalized covered the estimated EE.
PRO were administered in the amount of 1. An appropriate supply of essential fatty acids in the diet was ensured. Each of the subjects in study group received day menus.
Diets were developed considering the type of foods, cooking methods, and pre-established macronutrient ratios. All instructions about foods and meal preparation were provided by dieticians.
For food intake recording, the participants used food diaries and electronic kitchen scales. The dieticians gave instructions to each participant individually on how to use the scales and complete the diaries. Participants recorded the time and amount of foods and beverages consumed at each meal, the amount of leftovers, and any deviations from the diet. The diaries were collected at the T 1 and T 2 visits. A dietician reviewed and discussed the diary with each participant.
The participants were also encouraged to contact the dieticians or the other research team members if any side effects of KD occurred, e. Additionally, they were also asked about potential side effects during KD and at the T 2 visit. The total body water and hydration level were assessed by bioelectric impedance with Bodystat Bodystat Inc.
During the bioimpedance analyses, the recommended measurement conditions were strictly followed [ 52 ]. The total daily EE was assessed as described previously using heart rate HR monitoring data Polar RS, Vantaa, Finland , based on a previously validated method [ 50 , 53 , 54 ]. To eliminate any accidental errors e. The information was used to fill the potential gaps in HR recordings. Recorded wrist-worn HR data were downloaded to a computer equipped with the Polar ProTrainer 5 program ver.
The EE for each category was calculated as recommended, and four-day HR data were categorized into intensity levels and used to estimate the total daily EE [ 50 , 53 , 54 ].
In order to obtain confirmation of compliance with the KD regime by the subjects, the KB concentration was assessed in urine and blood samples. All blood samples were taken with the patient in a seated upright position. The apparatus measurement accuracy CV was 3. Throughout the study protocol, the subjects performed two exercise tests T 1 — 2. The incremental cycling tests ICT were performed under standardized conditions temp. Prior to each test, the subjects were instructed about its procedure and completed a brief 5-min warm-up on a cycloergometer Kettler-X1, Kettler, Ense-Parsit, Germany Fig.
Every 1. VO 2max was defined as the point where a workload increase stopped generating further increases in oxygen uptake VO 2 and HR [ 57 , 58 ].
Although all participants were familiar with the tests from T 0 as well as from previous studies and training, they were encouraged to ask questions about the details of the protocol. Furthermore, the subjects were asked to wear proper workout clothing and shoes. All testing was supervised by an experienced researcher. Due to significant differences in body composition in females and males, all the results substrate oxidation rate and EE are given in relation to fat free mass FFM content.
Based on other studies that have evaluated nutritional interventions with KD on energy metabolism during exercise, a sample size of eight to eleven per group was deemed to be common [ 41 , 42 , 43 , 44 , 45 , 59 ]. Therefore, an initial sample size of 11 per group females and males was selected.
The power analysis was performed based on the following inputs: t-test differences between two dependent means matched pairs or ANOVA repeated measures between-factors; an alpha value of 0. The results indicated that a standardized effect size of 0. Furthermore, based on our pilot study and previous studies on different dietary regimes on energy metabolism [ 50 ], we assumed that a sample size of 11 in each group females and males would be sufficient to detect significant differences in fat oxidation.
Importantly, in the context of results interpretation, we did not observe significant changes in VO 2 max under KD Table 1. On the other hand, reported inconveniences resulting from the conversion of energy processes related to the use of glucose in favor of KB were irritability, drowsiness, and changes in mood. In some of the subjects, none of the above ailments occurred, while in athletes who had difficulty with ketoadaptation, the symptoms lasted from a few days to a maximum of a week.
This aspect was also one of the reasons for the resignation of some study participants. Apart from low supply of fiber, the KD during the study protocol was characterized by high nutritional value with regard to vitamins and minerals. The intake of most of them did not changed or was even higher during KD. From 30 participants, eight did not complete the study either due to injury 1 female and 1 male or non-adherence to the protocol and failure to achieve a state of ketosis 2 females and 4 males Fig.
Twenty-two participants 11 females and 11 males met the criteria required in the study protocol, completed the nutritional intervention periods and two visits T 1—2 , and reported no significant lifestyle and training routine changes during the study.
In males, the rate of fat oxidation during the KD was higher throughout the whole exercise as compared to CD testing Fig. In contrast, after KD, there were no significant between-gender differences at any point of VO 2 max testing Fig.
Keto Diet Athletes - TRANSPARÊNCIA
The ketogenic diet and sport: a possible marriage? Sport Sci. The ketogenic diet KD is used widely as a weight loss strategy and, more rarely, as therapy for some diseases. In many sports, weight control is often necessary boxing, weightlifting, wrestling, etc. Key Words: ketogenic diet, endurance, strength, weight loss, skeletal muscle hypertrophy health.
Metrics details. The ketogenic diet is becoming a popular nutritional model among athletes. However, the relationship between its use and metabolism during exercise seems to have not been fully investigated. During the ICT while consuming the customary diet and after the KD , oxygen uptake and carbon dioxide exhalation were registered, and CHO and fat utilization as well as energy expenditure were calculated. Male CrossFit-trained athletes seem to be more prone to shifts in macronutrient utilization in favor of fat utilization during submaximal intensity exercise under a ketogenic diet than are female athletes.
The Ketogenic Diet and Sport: A Possible Marriage?
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Sport Mont , 18 1 , DOI: Many athletes are concerned about attaining or maintaining optimal body weight and composition for their sport. Athletes may want to reduce body weight to ensure optimal performance, to improve aesthetic appearance, or to compete in weight category sports. This leads to efforts to reduce body fat without losing muscle mass and often to nutritional practices that may have severe health consequences.
Effect of a four-week ketogenic diet on exercise metabolism in CrossFit-trained athletes
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Recently, there has been a re-emerging interest in the role of ketone bodies in exercise metabolism, with considerable media speculation about ketone body supplements being routinely used by professional cyclists. Ketone bodies can serve as an important energy substrate under certain conditions, such as starvation, and can modulate carbohydrate and lipid metabolism. Dietary strategies to increase endogenous ketone body availability i. Recently, ketone body supplements ketone salts and esters have emerged and may be used to rapidly increase ketone body availability, without the need to first adapt to a ketogenic diet. However, the extent to which ketone bodies regulate skeletal muscle bioenergetics and substrate metabolism during prolonged endurance-type exercise of varying intensity and duration remains unknown. Nutrients consumed before and during exercise training can support optimal performance by delaying the onset of fatigue and assisting in the recovery process by replenishing endogenous substrates stores. Particularly for endurance-type sports characterized by high rates, and absolute levels of energy expenditure, appropriate nutrient intake is essential to fuel exercise, delay the deterioration in performance, and promote post-exercise recovery [ 1 — 5 ].
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