The effect of weight loss by ketogenic diet on the body composition, performance-related physical fitness factors and cytokines of Taekwondo athletes

The effect of the ketogenic diet on resistance training load management: a repeated-measures clinical trial in trained participants

BACKGROUND

The effect of low-carbohydrate high-fat dietary manipulation, such as the ketogenic diet (KD), on muscle strength assessment in resistance-training (RT) participants has focused on the one-repetition maximum test (1-RM). However, a pre-specified 1-RM value during an exercise training program disregards several confounding factors (i.e. sleep, diet, and training-induced fatigue) that affect the exerciser's "true" load and daily preparedness. We aimed to evaluate the effect of a 6-week RT program on load control-related variables in trained subjects following a KD intervention.

METHODS

Fourteen resistance-trained individuals (3F, 11 M; 30.1 [6.2] years; 174.2 [7.6] cm; 75.7 [10.8] kg; BMI 24.8 [2.1] kg·m-2) completed this single-arm repeated-measures clinical trial. Load management variables included volume load, number of repetitions, perceived exertion (RPE), movement velocity loss, and exertion index. These primary outcomes were assessed weekly before, during, and at the end of a 6-week RT program that included traditional RT exercises (bench press, femoral lying down, lat pulldown, leg extension, and back squat).

RESULTS

There was a significant difference in RPE between weeks (p = 0.015, W = 0.19) with a slight trend in decreasing RPE. We found differences in the volume load per week (p < 0.001; W = 0.73 and p < 0.001, W = 0.81, respectively), with an increase in the last weeks. In the control of the load based on movement velocity, we did not find significant differences between weeks (p = 0.591, W = 0.06), although significant differences were found in the effort index (p = 0.026, W = 0.17).

CONCLUSIONS

A KD diet in recreational strength participants does not appear to lead to performance losses during a RT program aimed at improving body composition. However, the lack of adherence and familiarity with the ketogenic diet must be considered specially during first weeks.

International society of sports nutrition position stand: ketogenic diets

POSITION STATEMENT

The International Society of Sports Nutrition (ISSN) provides an objective and critical review of the use of a ketogenic diet in healthy exercising adults, with a focus on exercise performance and body composition. However, this review does not address the use of exogenous ketone supplements. The following points summarize the position of the ISSN.

1. A ketogenic diet induces a state of nutritional ketosis, which is generally defined as serum ketone levels above 0.5 mM. While many factors can impact what amount of daily carbohydrate intake will result in these levels, a broad guideline is a daily dietary carbohydrate intake of less than 50 grams per day.

2. Nutritional ketosis achieved through carbohydrate restriction and a high dietary fat intake is not intrinsically harmful and should not be confused with ketoacidosis, a life-threatening condition most commonly seen in clinical populations and metabolic dysregulation.

3. A ketogenic diet has largely neutral or detrimental effects on athletic performance compared to a diet higher in carbohydrates and lower in fat, despite achieving significantly elevated levels of fat oxidation during exercise (~1.5 g/min).

4. The endurance effects of a ketogenic diet may be influenced by both training status and duration of the dietary intervention, but further research is necessary to elucidate these possibilities. All studies involving elite athletes showed a performance decrement from a ketogenic diet, all lasting six weeks or less. Of the two studies lasting more than six weeks, only one reported a statistically significant benefit of a ketogenic diet.

5. A ketogenic diet tends to have similar effects on maximal strength or strength gains from a resistance training program compared to a diet higher in carbohydrates. However, a minority of studies show superior effects of non-ketogenic comparators.

6. When compared to a diet higher in carbohydrates and lower in fat, a ketogenic diet may cause greater losses in body weight, fat mass, and fat-free mass, but may also heighten losses of lean tissue. However, this is likely due to differences in calorie and protein intake, as well as shifts in fluid balance.

7. There is insufficient evidence to determine if a ketogenic diet affects males and females differently. However, there is a strong mechanistic basis for sex differences to exist in response to a ketogenic diet.

Problems and Opportunities in the use of Bioelectrical Impedance Analysis for Assessing Body Composition During Ketogenic Diets: A Scoping Review

PURPOSE OF THE REVIEW

The use of bioelectrical impedance analysis (BIA) for monitoring body composition during the ketogenic diet has experienced a rapid surge. This scoping review aimed to assess the validity of procedures applying BIA in the ketogenic diet and to suggest best practices for optimizing its utilization.

RECENT FINDINGS

We conducted a systematic scoping review of peer-reviewed literature involving BIA for assessing body composition in individuals adhering to a ketogenic diet. Searches of international databases yielded 1609 unique records, 72 of which met the inclusion criteria and were reviewed. Thirty-five studies used foot-to-hand technology, 34 used standing position technology, while 3 did not declare the technology used. Raw bioelectrical parameters were reported in 21 studies. A total of 196 body mass components were estimated, but predictive equations were reported in only four cases. Most research on BIA during ketogenic diets did not report the equations used for predicting body composition, making it impossible to assess the validity of BIA outputs. Furthermore, the exceedingly low percentage of studies reporting and analyzing raw data makes it challenging to replicate methodologies in future studies, highlighting that BIA is not being utilized to its full potential. There is a need for more precise technology and device characteristics descriptions, full report of raw bioelectrical data, and predictive equations utilized. Moreover, evaluating raw data through vectorial analysis is strongly recommended. Eventually, we suggest best practices to enhance BIA outcomes during ketogenic diets.

Does the Paleo diet affect an athlete's health and sport performance?

The aim of the study was to assess the impact of an eight-week Paleo diet on the health status (body composition, haematology and biochemistry of blood and urine) and the level of physical capacity (aerobic and anaerobic) of professional handball players. Fifteen athletes were assigned to two groups: 9 in the experimental group (PD) and 6 in the control group (CD). Significant decreases in body mass (BM), body mass index (BMI), and fat mass (FM) as well as an increase in the fat-free mass (FFM) (%) in both groups were observed. There were no significant differences between groups in particular series during the experiment in all haematological and biochemical indicators of blood and urine. Only HDL-C was significantly higher in the last series in the PD compared to the CD (1.63 mmol/l vs. 1.23 mmol/l). In the Wingate test, there were only single intragroup changes, consisting of a significant decrease in the Wt, MAP and Pmean in the experimental group. There were no significant differences between the groups in individual series or intragroup differences during the experiment, determined by the VO2max, VEmax, VE ∙ VCO2 -1, RER, and the time of the test with a gradually increasing load on a treadmill, except for a significant decrease of maximum tidal volume (TVmax) in the PD. No adverse effect of the Paleo diet on the health status was found. The use of the Paleo diet slightly adversely affects anaerobic capacity and does not affect the level of aerobic capacity.

Low- or moderate-carbohydrate calorie-restricted diets have similar effects on body composition and taekwondo performance after high-carbohydrate recovery meals

Low-carbohydrate (LC) diets are popular among general and athletic populations attempting to lose body mass. This study investigated the effect of a 7-day LC or moderate-carbohydrate (MC) calorie-restricted diet followed by 18-h recovery on body composition and taekwondo-specific performance. In this randomised cross-over study, 12 male taekwondo athletes consumed an LC (10% of carbohydrate, 41% of protein, 49% of fat, and 15.8 ± 0.4 kcal/kg/day) or an isocaloric MC diet (60% of carbohydrate, 30% of protein, and 10% of fat) for 7 days. The participants then consumed a carbohydrate-rich recovery dinner (39.2 ± 3.1 kcal/kg) followed by breakfast (6.2 ± 0.4 kcal/kg) in both the trials. Three repeated sprint ability (RSA) tests were conducted after breakfast. The taekwondo-specific reaction battery was administered before the first RSA test and after each RSA test. The participants experienced similar magnitudes of significant loss of body mass in the LC (-2.4 ± 1.7%) and MC (-2.3 ± 1.7%) trials. Fat mass and fat percentage significantly decreased in the MC trial but remained unchanged in the LC trial after body mass loss. Fat free mass was maintained in both the trials. The average and peak power in the RSA tests and the premotor reaction time were similar between the trials. The participants experienced significantly higher fatigue in the LC trial. In conclusion, both the diets can help athletes rapidly lose body mass while maintaining performance as long as an adequate amount of carbohydrate is consumed during the recovery period.

Effects of the Ketogenic Diet on Muscle Hypertrophy in Resistance-Trained Men and Women: A Systematic Review and Meta-Analysis

Reviews focused on the ketogenic diet (KD) based on the increase in fat-free mass (FFM) have been carried out with pathological populations or, failing that, without population differentiation. The aim of this review and meta-analysis was to verify whether a ketogenic diet without programmed energy restriction generates increases in fat-free mass (FFM) in resistance-trained participants. We evaluated the effect of the ketogenic diet, in conjunction with resistance training, on fat-free mass in trained participants. Boolean algorithms from various databases (PubMed, Scopus. and Web of Science) were used, and a total of five studies were located that related to both ketogenic diets and resistance-trained participants. In all, 111 athletes or resistance-trained participants (87 male and 24 female) were evaluated in the studies analyzed. We found no significant differences between groups in the FFM variables, and more research is needed to perform studies with similar ketogenic diets and control diet interventions. Ketogenic diets, taking into account the possible side effects, can be an alternative for increasing muscle mass as long as energy surplus is generated; however, their application for eight weeks or more without interruption does not seem to be the best option due to the satiety and lack of adherence generated.

Ketogenic diets, physical activity and body composition: a review

Obesity remains a serious relevant public health concern throughout the world despite related countermeasures being well understood (i.e. mainly physical activity and an adjusted diet). Among different nutritional approaches, there is a growing interest in ketogenic diets (KD) to manipulate body mass (BM) and to enhance fat mass loss. KD reduce the daily amount of carbohydrate intake drastically. This results in increased fatty acid utilisation, leading to an increase in blood ketone bodies (acetoacetate, 3-β-hydroxybutyrate and acetone) and therefore metabolic ketosis. For many years, nutritional intervention studies have focused on reducing dietary fat with little or conflicting positive results over the long term. Moreover, current nutritional guidelines for athletes propose carbohydrate-based diets to augment muscular adaptations. This review discusses the physiological basis of KD and their effects on BM reduction and body composition improvements in sedentary individuals combined with different types of exercise (resistance training or endurance training) in individuals with obesity and athletes. Ultimately, we discuss the strengths and the weaknesses of these nutritional interventions together with precautionary measures that should be observed in both individuals with obesity and athletic populations. A literature search from 1921 to April 2021 using Medline, Google Scholar, PubMed, Web of Science, Scopus and Sportdiscus Databases was used to identify relevant studies. In summary, based on the current evidence, KD are an efficient method to reduce BM and body fat in both individuals with obesity and athletes. However, these positive impacts are mainly because of the appetite suppressive effects of KD, which can decrease daily energy intake. Therefore, KD do not have any superior benefits to non-KD in BM and body fat loss in individuals with obesity and athletic populations in an isoenergetic situation. In sedentary individuals with obesity, it seems that fat-free mass (FFM) changes appear to be as great, if not greater, than decreases following a low-fat diet. In terms of lean mass, it seems that following a KD can cause FFM loss in resistance-trained individuals. In contrast, the FFM-preserving effects of KD are more efficient in endurance-trained compared with resistance-trained individuals.

Rapid Weight Loss of Up to Five Percent of the Body Mass in Less Than 7 Days Does Not Affect Physical Performance in Official Olympic Combat Athletes With Weight Classes: A Systematic Review With Meta-Analysis

Given the relevance of the effects that weight loss can generate on the physical performance in athletes, this study performed a systematic review with meta-analysis of the published literature on rapid weight loss (RWL) and examined its impact on the physical performance in Official Olympic combat sports athletes. The “Preferred Reporting Items for Systematic Reviews and Meta-Analysis” (PRISMA) guidelines were followed to ensure an ethical and complete reporting of the findings. PubMed, SPORT Discus, and EBSCO were the electronic databases explored for article retrieval and selection. The following string was applied: “RWL” OR “weight loss” OR “weight reduction” AND “judo” OR “wrestling” or “taekwondo” or “boxing” AND “performance.” Based on the quality analysis, conducted according to the “Tool for the assessment of study quality and reporting in exercise training studies” (TESTEX), ten articles achieved a score >6 points. The meta-analysis showed a significant difference in pre- vs. post-weight loss (p = 0.003) and no effects in pre- vs. post-power and strength performance analysis (p > 0.05 for both results). Based on our systematic review and meta-analysis of the literature, RWL up to ≤5% of the body mass in less than 7 days does not influence performance outcomes in Official Olympic combat athletes with weight classes, considering the strength and power measures.

The Effect of Carbohydrate Intake on Strength and Resistance Training Performance: A Systematic Review

High carbohydrate intakes are commonly recommended for athletes of various sports, including strength trainees, to optimize performance. However, the effect of carbohydrate intake on strength training performance has not been systematically analyzed. A systematic literature search was conducted for trials that manipulated carbohydrate intake, including supplements, and measured strength, resistance training or power either acutely or after a diet and strength training program. Studies were categorized as either (1) acute supplementation, (2) exercise-induced glycogen depletion with subsequent carbohydrate manipulation, (3) short-term (2–7 days) carbohydrate manipulation or (4) changes in performance after longer-term diet manipulation and strength training. Forty-nine studies were included: 19 acute, six glycogen depletion, seven short-term and 17 long-term studies. Participants were strength trainees or athletes (39 studies), recreationally active (six studies) or untrained (four studies). Acutely, higher carbohydrate intake did not improve performance in 13 studies and enhanced performance in six studies, primarily in those with fasted control groups and workouts with over 10 sets per muscle group. One study found that a carbohydrate meal improved performance compared to water but not in comparison to a sensory-matched placebo breakfast. There was no evidence of a dose-response effect. After glycogen depletion, carbohydrate supplementation improved performance in three studies compared to placebo, in particular during bi-daily workouts, but not in research with isocaloric controls. None of the seven short-term studies found beneficial effects of carbohydrate manipulation. Longer-term changes in performance were not influenced by carbohydrate intake in 15 studies; one study favored the higher- and one the lower-carbohydrate condition. Carbohydrate intake per se is unlikely to strength training performance in a fed state in workouts consisting of up to 10 sets per muscle group. Performance during higher volumes may benefit from carbohydrates, but more studies with isocaloric control groups, sensory-matched placebos and locally measured glycogen depletion are needed.

Recent Progress in Applicability of Exercise Immunology and Inflammation Research to Sports Nutrition

This article focuses on how nutrition may help prevent and/or assist with recovery from the harmful effects of strenuous acute exercise and physical training (decreased immunity, organ injury, inflammation, oxidative stress, and fatigue), with a focus on nutritional supplements. First, the effects of ketogenic diets on metabolism and inflammation are considered. Second, the effects of various supplements on immune function are discussed, including antioxidant defense modulators (vitamin C, sulforaphane, taheebo), and inflammation reducers (colostrum and hyperimmunized milk). Third, how 3-hydroxy-3-methyl butyrate monohydrate (HMB) may offset muscle damage is reviewed. Fourth and finally, the relationship between exercise, nutrition and COVID-19 infection is briefly mentioned. While additional verification of the safety and efficacy of these supplements is still necessary, current evidence suggests that these supplements have potential applications for health promotion and disease prevention among athletes and more diverse populations.

Effects of Combining a Ketogenic Diet with Resistance Training on Body Composition, Strength, and Mechanical Power in Trained Individuals: A Narrative Review

Ketogenic diets (KD) have gained popularity in recent years among strength-trained individuals. The present review summarizes current evidence—with a particular focus on randomized controlled trials—on the effects of KD on body composition and muscle performance (strength and power output) in strength-trained individuals. Although long-term studies (>12 weeks) are lacking, growing evidence supports the effectiveness of an ad libitum and energy-balanced KD for reducing total body and fat mass, at least in the short term. However, no or negligible benefits on body composition have been observed when comparing hypocaloric KD with conventional diets resulting in the same energy deficit. Moreover, some studies suggest that KD might impair resistance training-induced muscle hypertrophy, sometimes with concomitant decrements in muscle performance, at least when expressed in absolute units and not relative to total body mass (e.g., one-repetition maximum). KD might therefore be a beneficial strategy for promoting fat loss, although it might not be a recommendable option to gain muscle mass and strength/power. More research is needed on the adoption of strategies for avoiding the potentially detrimental effect of KD on muscle mass and strength/power (e.g., increasing protein intake, reintroduction of carbohydrates before competition). In summary, evidence is as yet scarce to support a major beneficial effect of KD on body composition or performance in strength-trained individuals. Furthermore, the long-term effectiveness and safety of this type of diet remains to be determined.

High-Protein Energy-Restriction: Effects on Body Composition, Contractile Properties, Mood, and Sleep in Active Young College Students

Background: It is often advised to ensure a high-protein intake during energy-restricted diets. However, it is unclear whether a high-protein intake is able to maintain muscle mass and contractility in the absence of resistance training. Materials and Methods: After 1 week of body mass maintenance (45 kcal/kg), 28 male college students not performing resistance training were randomized to either the energy-restricted (ER, 30 kcal/kg, n = 14) or the eucaloric control group (CG, 45 kcal/kg, n = 14) for 6 weeks. Both groups had their protein intake matched at 2.8 g/kg fat-free-mass and continued their habitual training throughout the study. Body composition was assessed weekly using multifrequency bioelectrical impedance analysis. Contractile properties of the m. rectus femoris were examined with Tensiomyography and MyotonPRO at weeks 1, 3, and 5 along with sleep (PSQI) and mood (POMS). Results: The ER group revealed greater reductions in body mass (Δ -3.22 kg vs. Δ 1.90 kg, p < 0.001, partial η ² = 0.360), lean body mass (Δ -1.49 kg vs. Δ 0.68 kg, p < 0.001, partial η ² = 0.152), body cell mass (Δ -0.85 kg vs. Δ 0.59 kg, p < 0.001, partial η ² = 0.181), intracellular water (Δ -0.58 l vs. Δ 0.55 l, p < 0.001, partial η ² = 0.445) and body fat percentage (Δ -1.74% vs. Δ 1.22%, p < 0.001, partial η ² = 433) compared to the CG. Contractile properties, sleep onset, sleep duration as well as depression, fatigue and hostility did not change (p > 0.05). The PSQI score (Δ -1.43 vs. Δ -0.64, p = 0.006, partial η ² = 0.176) and vigor (Δ -2.79 vs. Δ -4.71, p = 0.040, partial η ² = 0.116) decreased significantly in the ER group and the CG, respectively. Discussion: The present data show that a high-protein intake alone was not able to prevent lean mass loss associated with a 6-week moderate energy restriction in college students. Notably, it is unknown whether protein intake at 2.8 g/kg fat-free-mass prevented larger decreases in lean body mass. Muscle contractility was not negatively altered by this form of energy restriction. Sleep quality improved in both groups. Whether these advantages are due to the high-protein intake cannot be clarified and warrants further study. Although vigor was negatively affected in both groups, other mood parameters did not change.

Paleolithic Diet-Effect on the Health Status and Performance of Athletes?

The aim of this meta-analysis was to review the impact of a Paleolithic diet (PD) on selected health indicators (body composition, lipid profile, blood pressure, and carbohydrate metabolism) in the short and long term of nutrition intervention in healthy and unhealthy adults. A systematic review of randomized controlled trials of 21 full-text original human studies was conducted. Both the PD and a variety of healthy diets (control diets (CDs)) caused reduction in anthropometric parameters, both in the short and long term. For many indicators, such as weight (body mass (BM)), body mass index (BMI), and waist circumference (WC), impact was stronger and especially found in the short term. All diets caused a decrease in total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG), albeit the impact of PD was stronger. Among long-term studies, only PD cased a decline in TC and LDL-C. Impact on blood pressure was observed mainly in the short term. PD caused a decrease in fasting plasma (fP) glucose, fP insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) and glycated hemoglobin (HbA1c) in the short run, contrary to CD. In the long term, only PD caused a decrease in fP glucose and fP insulin. Lower positive impact of PD on performance was observed in the group without exercise. Positive effects of the PD on health and the lack of experiments among professional athletes require longer-term interventions to determine the effect of the Paleo diet on athletic performance.

Influences of Ketogenic Diet on Body Fat Percentage, Respiratory Exchange Rate, and Total Cholesterol in Athletes: A Systematic Review and Meta-Analysis

(1) Background: The purpose of the current meta-analysis was to investigate any positive or negative effects of ketogenic diets in athletes and provide an assessment of the size of these effects. (2) Methods: Databases were used to select relevant studies up to January 2021 regarding the effects of ketogenic diets in athletes. Inclusion criteria were as follows: data before and after ketogenic diet use, being randomized controlled trials and presenting ketogenic diets and assessments of ketone status. Study subjects were required to be professional athletes. Review studies, pilot studies, and studies in which non-athletes were included were excluded from this meta-analysis. The outcome effect sizes in these selected studies were calculated by using the standardized mean difference statistic. (3) Results: Eight studies were selected for this meta-analysis. Athletes who consumed the ketogenic diet had reduced body fat percentages, respiratory exchange rates, and increased total cholesterol compared to athletes who did not consume this diet. However, body mass index, cardiorespiratory fitness, heart rate, HDL cholesterol, glucose level, and insulin level were unaffected by the diet. (4) Conclusions: Ketogenic diets had a beneficial effect by decreasing body fat percentage, but athletes with high total cholesterol level need to be monitored when instituting a ketogenic diet. Our study sample size was limited; therefore, additional studies may be needed to confirm the current findings. Further studies need to be conducted on changes in LDL cholesterol, HDL cholesterol, total cholesterol and ratio of LDL to HDL cholesterol.

Effects of resistance training combined with a ketogenic diet on body composition: a systematic review and meta-analysis

We evaluated the effects of ketogenic diets (KDs) on body mass (BM), fat mass (FM), fat-free mass (FFM), body mass index (BMI), and body fat percentage (BFP) compared to non-KDs in individuals performing resistance training (RT). Online electronic databases including PubMed, the Cochrane Library, Web of Science, Embase, SCOPUS, and Ovid were searched to identify initial studies until February 2021. Data were pooled using both fixed and random-effects methods and were expressed as weighted mean difference (WMD) and 95% confidence intervals (CI). Out of 1372 studies, 13 randomized controlled trials (RCTs) that enrolled 244 volunteers were included. The pooled results demonstrated that KDs significantly decreased BM [(WMD = -3.67 kg; 95% CI: -4.44, -2.90, p < 0.001)], FM [(WMD = -2.21 kg; 95% CI: -3.09, -1.34, p < 0.001)], FFM [(WMD = -1.26 kg; 95% CI: -1.82, -0.70, p < 0.001)], BMI [(WMD = -1.37 kg.m^-2; 95% CI: -2.14, -0.59, p = 0.022)], and BFP [(WMD = -2.27%; 95% CI: -3.63, -0.90, p = 0.001)] compared to non-KDs. We observed beneficial effects of KDs compared to non-KDs on BM and body fat (both FM and BFP) in individuals performing RT. However, adherence to KDs may have a negative effect on FFM, which is not ameliorated by the addition of RT.

Reliability and diagnostic performance of a new blood ketone and glucose meter in humans

BACKGROUND

Accurate and reliable monitoring of blood ketone and glucose levels is useful for athletes adhering to a ketogenic diet who want to verify that they are in a state of ketosis and, therefore, accruing performance adaptations. However, the cost of devices and testing materials may prohibit their use. More affordable field testing systems are available, but their accuracy and reliability remain in question. The objectives of this study were to evaluate the agreement between a previously validated ketone and glucose meter (Meter 1 - Precision Xtra) and a more affordable meter that has not been validated (Meter 2 - Keto-Mojo), and also to assess the diagnostic performance of Meter 2 for identifying nutritional ketosis.

METHODS

Thirteen participants (7 females and 6 males; 21.6 ± 3.0 years old) visited the laboratory three times in this randomized, double-blind cross-over design study. Ketone and glucose levels were measured with Meter 1 and Meter 2 twice before and twice after ingestion of a racemic ketone, natural ketone, or maltodextrin supplement. Intraclass correlation coefficient (ICC) estimates and their 95% confidence intervals were calculated to evaluate interrater reliability for Meter 1 and Meter 2. Bland-Altman plots were constructed to visually assess the agreement between devices. Area under the ROC curve analysis was performed to evaluate the diagnostic ability of Meter 2 to detect nutritional ketosis at a threshold ketone level of 0.5 mM as identified by Meter 1.

RESULTS

Reliability between the meters was excellent for measuring ketones (ICC = .968; .942-.981) and good for measuring glucose (ICC = .809; .642-.893), though the Bland-Altman plot revealed substantial differences in agreement for measuring glucose. Area under the ROC curve (Area = 0.913; 0.828-0.998) was excellent for diagnosing nutritional ketosis.

CONCLUSIONS

Both Meter 1 and Meter 2 displayed excellent agreement between each other for ketone measurement. Meter 2 also displayed an excellent level of accuracy for diagnosing nutritional ketosis at a threshold value of 0.5 mM, making it an effective and affordable alternative to more expensive testing devices.

Role of a Ketogenic Diet on Body Composition, Physical Health, Psychosocial Well-Being and Sports Performance in Athletes: A Scoping Review

BACKGROUND

Recently, a focus has been placed on investigating the potential benefits of adherence to a ketogenic diet in enhancing body composition, physical health, psychological well-being, and performance of athletes from various sporting disciplines. As the available research is yet to be collated and analyzed in a single review, this scoping review aims to analyze and draw conclusions from the available literature that exists on the efficacy of a ketogenic diet among athletic populations.

METHODS

Several primary research databases and any relevant citation lists were searched to locate appropriate studies for inclusion in this scoping review. Studies that investigated the effects of adherence to a ketogenic diet (KD), defined by a carbohydrate intake of less than 5% of total energy intake, on body composition, physical health, psychological well-being, and performance among an athletic population were included in the review. From 814 articles screened, 12 were identified as meeting the inclusion criteria and were included in the final scoping review.

RESULTS

Adherence to a KD has beneficial effects on body weight and fat mass. Varying effects were identified on physical health with the diet, eliciting positive effects on fat oxidation but potentially deleterious effects on stool microbiota and iron metabolism. Conflicting results were reported regarding the effects of a KD on sporting performance. Benefits were reported regarding athlete well-being following commencement of a KD, but only after week two.

CONCLUSIONS

The results of this scoping review demonstrate that there are both beneficial and detrimental effects associated with adherence to a KD among athletic populations. It is understood that further research is required to make any concrete recommendations regarding a KD to athletes.

Changes in body composition and substrate utilization after a short-term ketogenic diet in endurance-trained males

Few studies have investigated the short-term effects of a very low carbohydrate ketogenic diet (KD) on body composition and substrate utilization in trained individuals. This study investigated effects on substrate utilization during incremental exercise, and changes in body composition, in response to seven days ad libitum consumption of a KD by athletes from endurance sports. Nine young trained males (age, 21.8 ± 1.9 y; height, 1.83 ± 0.11 m; body mass, 78.4 ± 13.8 kg; body fat, 14.9 ± 3.9%; VO2peak, 54.3 ± 5.9 mL kg^-1 min^-1) were assessed before (day 0; PRE) and after (day 7; POST) seven days of consuming an ad libitum KD. Following an overnight fast, body composition was measured by dual x-ray absorptiometry, and substrate utilization was measured during an incremental (3 min stages, 35 W increments) exercise test on a cycle ergometer. After KD, W_max (PRE, 295 ± 30 W; POST, 292 ± 38 W) and VO2peak (PRE, 4.18 ± 0.33 L min^-1; POST, 4.10 ± 0.43 L min^-1) were unchanged, whereas body mass [-2.4 (-3.2, -1.6) kg; P < 0.001, d = 0.21], fat mass [-0.78 (-1.10, -0.46) kg; P < 0.001, d = 0.22] and fat-free mass (FFM) [-1.82 (-3.12, -0.51) kg; P = 0.013, d = 0.22] all decreased. The respiratory exchange ratio was lower, and rates of fat oxidation were higher, at POST across a range of exercise intensities. Maximal fat oxidation rate was ~1.8-fold higher after KD (PRE, 0.54 ± 0.13 g min^-1; POST, 0.95 ± 0.24 g min^-1; P < 0.001, d = 2.2). Short-term KD results in loss of both fat mass and FFM, increased rates of fat oxidation and a concomitant reduction in CHO utilization even at moderate-to-high intensities of exercise.

A 3-Week, Low-Carbohydrate, High-Fat Diet Improves Multiple Serum Inflammatory Markers in Endurance-Trained Males

Waldman, HS, Heatherly, AJ, Killen, LG, Hollingsworth, A, Koh, Y, and O'Neal, EK. A three-week, low-carbohydrate, high-fat diet improves multiple serum inflammatory markers in endurance-trained males. J Strength Cond Res XX(X): 000-000, 2020-This study examined the effects of a low-carbohydrate, high-fat diet (LCHF) on inflammatory marker responses in middle-aged endurance athletes. Eight male runners maintained their habitual mixed diet (HMD) in the first phase of the study before switching to a noncalorically restricted LCHF diet (∼70% of kcals from fat; carbohydrate <50 g) for 3 weeks. Subjects completed a 50-minute fixed pace treadmill running protocol in a hot environment, followed by a 5-km outdoor time trial. Fasting serum samples were collected immediately after exercise and heat stress restriction, and again 24 hours after the exercise/heat stressor. Thirty inflammation markers were assessed using the multiplex flow immunoassay technique. Seven markers (BAFF/TNFSF-13, sCD30/TNFRSF8, sCD163, Chitinase3-like1, gp130SIL-6Rβ, sTNFR-1, and sTNFR-2) reached statistical significance (p < 0.05) favoring LCHF before exercise, and sCD30/TNFRSF8 favored (p < 0.05) LCHF before (HMD = 459 ± 111; LCHF = 296 ± 100) and after (HMD = 385 ± 104; LCHF = 285 ± 104 pg·ml) exercise. Although the current dietary intervention was short in duration, LCHF seems to offer some protection against multiple chronic inflammation markers for physically active men between ages 30 and 50 years.

Application of nutrient essentiality criteria to dietary carbohydrates

The purpose of the present review is to describe how human physiology at very low carbohydrate intakes relates to the criteria for nutritional essentiality. Although we did not limit ourselves to one particular type or function of carbohydrates, we did primarily focus on glucose utilisation as that function was used to determine the recommended daily allowance. In the general population, the human body is able to endogenously synthesise carbohydrates, and does not show signs of deficiency in the absence of dietary carbohydrates. However, in certain genetic defects, such as glycogen storage disease type I, absence of dietary carbohydrates causes abnormalities that are resolved with dietary supplementation of carbohydrates. Therefore, dietary carbohydrates may be defined as conditionally essential nutrients because they are nutrients that are not required in the diet for the general population but are required for specific subpopulations. Ketosis may be considered a physiological normal state due to its occurrence in infants in addition to at very low carbohydrate intakes. Although sources of dietary carbohydrates can provide beneficial micronutrients, no signs of micronutrient deficiencies have been reported in clinical trials of low-carbohydrate ketogenic diets. Nonetheless, more research is needed on how micronutrient requirements can change depending on the dietary and metabolic context. More research is also needed on the role of dietary fibre during a low-carbohydrate ketogenic diet as the beneficial effects of dietary fibre were determined on a standard diet and several studies have shown beneficial effects of decreasing non-digestible carbohydrates.

Ergogenic Properties of Ketogenic Diets in Normal-Weight Individuals: A Systematic Review

Ketogenic diets (KDs) have received increasing attention among athletes and physically active individuals. However, the question as to whether and how the diet could benefit this healthy cohort remains unclear.Purpose: This study was designed to systematically review the existing evidence concerning the effect of KDs on body composition, aerobic and anaerobic capacity, muscle development, and sports performance in normal-weight individuals including athletes.Methods: A systematic search of English literature was conducted through electronic databases including PubMed, EBSCOhost, and Google Scholar. Upon the use of search criteria, 23 full-text original human studies involving non-obese participants were included in this review. For more stratified and focused analysis, these articles were further categorized based on the outcomes being examined including 1) body mass (BM) and %fat, 2) substrate utilization, 3) blood substrate and hormonal responses, 4) aerobic capacity and endurance performance, and 5) strength, power, and anaerobic capacity.Results: Our review indicates that a non-calorie-restricted KD carried out for ≥3 weeks can produce a modest reduction in BM and %fat, while maintaining fat-free mass. This diet leads to augmented use of fat as fuel, but this adaptation doesn't seem to improve endurance performance. Additionally, ad libitum KDs combined with resistance training will pose no harm to developing strength and power, especially when protein intake is increased modestly.Conclusions: It appears that a non-calorie-restricted KD provides minimal ergogenic benefits in normal-weight individuals including athletes, but can be used for optimizing BM and body composition without compromising aerobic and anaerobic performance. Key teaching pointsKetogenic diets have received increasing attention among athletes and physically active individuals.It remains elusive as to whether ketogenic diets could confer ergogenic benefits for those who are normal weight but want to use the diet to improve fitness and performance.An interesting dilemma exists in that ketogenic diets can reduce body mass and %fat and increase fat oxidation, but they can also decrease glycogen stores and limit sports performance.This review concludes that a non-calorie-restricted ketogenic diet provides minimal ergogenic benefits in normal-weight individuals, but can be used to optimize body mass and composition without compromising athletic performance.This finding can be important for esthetic or weight-sensitive athletes because the diet may allow them to reach a target body mass without having to sacrifice athletic performance.The ketogenic diet-induced metabolic adaptations require a state of ketosis, and thus caution should be taken because an excessive increase in ketone bodies can be detrimental to health.

Affective and Enjoyment Responses to Short-Term High-Intensity Interval Training with Low-Carbohydrate Diet in Overweight Young Women

Low-carbohydrate diets (LCs) seem effective on weight reduction and maintenance. However, the affect and enjoyment of exercise during LCs is not clear. The purpose of the present study was to compare the psychological responses to high-intensity interval training (HIIT) and to moderate-intensity continuous training (MICT) during the consumption of a 4-week LC diet in overweight young women. With LCs (~10% carbohydrate, 65%–70% fat, 20%–25% protein), forty-three eligible women (age: 20.9 ± 3.1 years; body weight: 65.8 ± 8.2 kg) were randomly assigned to one of three groups: HIIT (10 sets of 6 s all-out cycling interspersed with 9 s of rest), MICT (30 min cycling at 50%–60% of peak oxygen consumption, V̇O_2peak) or no-exercise controls (CON). Anthropometric indices and V̇O_2peak were measured pre- and post-training. Feeling Scale (FS), Felt Arousal Scale (FAS), Exercise Enjoyment Scale (EES), and Physical Activity Enjoyment Scale (PACES) scores were collected before and immediately after each training session throughout the study. After intervention, all three groups reduced by more than 2.5 kg of body weight whereas both exercise groups improved ~15% V̇O_2peak. Participants in the HIIT and MICT group exhibited similar affect points as indicated by FS and FAS. Post-exercise enjoyment scores in PACES were lower in HIIT (73–78 points) than MICT (83–87 points) despite similarly positive responses being observed in EES (corresponding to ~4 points of a 7-point scale). Short-term LCs were effective in weight loss and exercise training had an additive improvement on cardiorespiratory fitness. The overweight young women had similar affect valence, arousal levels, and comparable pleasurable feelings to HIIT and MICT with LCs. Furthermore, as indicated by PACES, MICT was more enjoyable which may elicit better adherence, whereas HIIT with LCs seems to be more arduous despite its time-efficiency.

Impact Of Ketogenic Diet On Athletes: Current Insights

The impact of a ketogenic diet (KD) (<50 g/d carbohydrate, >75% fat) on athletic performance has sparked much interest and self-experimentation in the past 3-4 years. Evidence shows 3-4-week adaptations to a KD in endurance-trained athletes were associated with maintenance of moderate (46-63% VO_2max) and vigorous intensity (64-90% VO_2max) endurance exercise, while at intensities >70% VO_2max, increases in fat oxidation were associated with decreased economy (increased oxygen consumption), and in some cases, increased ratings of perceived exertion and heart rate. Two investigations in recreationally active endurance athletes noted no vigorous intensity exercise decrement following 3- and 12-week adaptations. Moderate (70-85% one repetition maximum) and near-maximal to maximal intensity (>85% 1RM) strength performance experienced no decrement following a 3-12-week KD adaptation. Beneficial effects were noted for 2000 m sprint and critical power test completed for short duration at vigorous intensity, while two additional tests noted no decrement. For sprint, near-maximal exercise (>91% VO_2max), benefit of the KD was observed for six-second sprint, while no decrement in performance was noted for two additional maximal tests. When protein is equated (grams per kilogram), one investigation noted no decrement in muscle hypertrophy, while one noted a decrement. One investigation with matched protein noted the KD group lost more body fat. In conclusion, moderate-to-vigorous intensity exercise experiences no decrement following adaptation to a KD. Decreases in exercise economy are observed >70% VO_2max in trained endurance athletes which may negate performance within field settings. Beneficial effects of the KD during short duration vigorous, and sprint bouts of exercises are often confounded by greater weight loss in the KD group. With more athletes pursuing carbohydrate-restricted diets (moderate and strict (KD)) for their proposed health benefits, more work is needed in the area to address both performance and health outcomes.

The potential contribution of impaired brain glucose metabolism to congenital Zika syndrome

The Zika virus (ZIKV) became a major worldwide public concern in 2015 due to the congenital syndrome which presents the highest risk during the first trimester of pregnancy and includes microcephaly and eye malformations. Several cellular, genetic and molecular studies have shown alterations in metabolic pathways, endoplasmic reticulum (ER) stress, immunity and dysregulation of RNA and energy metabolism both in vivo and in vitro. Here we summarise the main metabolic complications, with a particular focus on the possibility that brain energy metabolism is altered following ZIKV infection, contributing to developmental abnormalities. Brain energetic failure has been implicated in neurological conditions such as autism disorder and epilepsy, as well as in metabolic diseases with severe neurodevelopmental complications such as Glut-1 deficiency syndrome. Therefore, these energetic alterations are of wide-ranging interest as they might be directly implicated in congenital ZIKV syndrome. Data showing increased glycolysis during ZIKV infection, presumably required for viral replication, might support the idea that the virus can cause energetic stress in the developing brain cells. Consequences may include neuroinflammation, cell cycle dysregulation and cell death. Ketone bodies are non-glycolytic brain fuels that are produced during neonatal life, starvation or fasting, ingestion of high-fat low-carbohydrate diets, and following supplementation with ketone esters. We propose that dietary ketones might alter the course of the disease and could even provide some degree of prevention of ZIKV-associated abnormalities and potentially related neurological conditions characterised by brain glucose impairment.

Effect of a four-week ketogenic diet on exercise metabolism in CrossFit-trained athletes

BACKGROUND

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.

METHODS

The aim of the study was to assess the effects of a four-week ketogenic diet (KD) on fat and carbohydrate (CHO) utilization during an incremental cycling test (ICT) in CrossFit-trained female (n = 11) and male (n = 11) athletes. 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.

RESULTS

In males, the KD led to an increase in fat utilization (g·min- 1·kgFFM- 1 and % oxidation). It was particularly noticeable at exercise intensities up to 80% of VO2max. An increase in the area under the curve (AUC) was seen in males but not in females at up to ≤65% VO2max of fat utilization.

CONCLUSIONS

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.

TRIAL REGISTRATION

Clinical Trials Gov, NCT03665948 . Registered 11 September 2018 (retrospectively registered).

Anaerobic Performance after a Low-Carbohydrate Diet (LCD) Followed by 7 Days of Carbohydrate Loading in Male Basketball Players

Despite increasing interest among athletes and scientists on the influence of different dietary interventions on sport performance, the association between a low-carbohydrate, high-fat diet and anaerobic capacity has not been studied extensively. The aim of this study was to evaluate the effects of a low-carbohydrate diet (LCD) followed by seven days of carbohydrate loading (Carbo-L) on anaerobic performance in male basketball players. Fifteen competitive basketball players took part in the experiment. They performed the Wingate test on three occasions: after the conventional diet (CD), following 4 weeks of the LCD, and after the weekly Carbo-L, to evaluate changes in peak power (PP), total work (TW), time to peak power (TTP), blood lactate concentration (LA), blood pH, and bicarbonate (HCO₃⁻). Additionally, the concentrations of testosterone, growth hormone, cortisol, and insulin were measured after each dietary intervention. The low-carbohydrate diet procedure significantly decreased total work, resting values of pH, and blood lactate concentration. After the low-carbohydrate diet, testosterone and growth hormone concentrations increased, while the level of insulin decreased. After the Carbo-L, total work, resting values of pH, bicarbonate, and lactate increased significantly compared with the results obtained after the low-carbohydrate diet. Significant differences after the low-carbohydrate diet and Carbo-L procedures, in values of blood lactate concentration, pH, and bicarbonate, between baseline and post exercise values were also observed. Four weeks of the low-carbohydrate diet decreased total work capacity, which returned to baseline values after the carbohydrate loading procedure. Moreover, neither the low-carbohydrate feeding nor carbohydrate loading affected peak power.

No Modification in Blood Lipoprotein Concentration but Changes in Body Composition after 4 Weeks of Low Carbohydrate Diet (LCD) Followed by 7 Days of Carbohydrate Loading in Basketball Players

Recently, low carbohydrate diets have become very popular due to their numerous health benefits. Unfortunately, little is known about their chronic effects on the blood lipid profile and other cardiovascular disease risk factors in athletic populations. We compared the results of a four week, well-planned low carbohydrate diet (LCD) followed by seven days of carbohydrate loading (Carbo-L) on fasting lipids - triacylglycerol's (TAG), LDL-C, HDL-C, total cholesterol (TCh), glucose, insulin and HOMA-IR levels in 11 competitive basketball players. During the experiment, we also measured body mass (BM) and body composition changes: body fat (BF), % of body fat (PBF), and fat free mass (FFM). Both diet procedures significantly changed the fasting serum concentration of TAG (p < 0.05) and body fat content (kg and %) (p < 0.05), without negative changes in FFM. The Carbo-L procedure increased (p < 0.05) fasting glucose levels significantly. A LCD may be suggested for athletes who want to reduce body mass and fat content without compromising muscle mass. Several weeks on a LCD does not change the lipoprotein - LDL-C and HDL-C level significantly, while a seven-day Carb-L procedure may increase body fat content and fasting glucose concentration. Such dietary procedures are recommended for team sport athletes to reduce fat mass, lipid profile disorders and insulin resistance.

An 8-Week Ketogenic Diet Alternated Interleukin-6, Ketolytic and Lipolytic Gene Expression, and Enhanced Exercise Capacity in Mice

Adjusting dietary fat intake is reported to affect mitochondrial biogenesis and fatty acid oxidation (FAO), and thus may enhance exercise capacity. However, a high-fat diet where carbohydrate intake is not limited enough also makes it difficult for athletes to maintain weight, and may fail to force the body to utilize fat. As such, a low-carbohydrate, high-fat, ketogenic diet (KD) may be viable. We have previously reported that an eight-week KD enhances exercise capacity, and suggested the mechanism to be enhanced lipolysis and ketolysis. In the present study, we investigated how an eight-week KD alters mRNA expression during fatty acid mobilization, FAO and ketolysis. We found that an eight-week KD may remodel the lipid metabolism profile, thus contributing to influence exercise capacity. We also found that ketolysis, lipolysis and FAO adaptations may contribute to enhanced exhaustive exercise performance. Along with enhanced FAO capacity during exhaustive exercise, a KD may also alter IL-6 synthesis and secretion profile, thus contribute to fatty acid mobilization, ketolysis, lipolysis and preventing muscle damage. Both the lipid metabolism response and IL-6 secretion appeared to be muscle fiber specific. Taken together, the previous and present results reveal that an eight-week KD may enhance exercise performance by up-regulating ketolysis and FAO ability. Therefore, a KD may have the potential to prevent muscle damage by altering IL-6 secretion profile, indicating that a KD may be a promising dietary approach in endurance athletes, sports, and for injury prevention.

Effects of 16-week spinning and bicycle exercise on body composition, physical fitness and blood variables of middle school students

The purpose of this study was to investigate the effects of 16 weeks of spinning and bicycling exercises on body composition, physical fitness and blood variables in female adolescents. Subjects participated in this study were 24 female middle school students (12 spinning cycles, 12 general bicycles) attending to Seoul Yeoksam middle school. Each group was trained for 16 weeks, 3 times a week, and 1 hr per day after school. Body composition, physical fitness (1,200 running, sit-ups, back strength, sit and reach, side-steps) and blood variables (low-density lipoprotein cholesterol, glucose, reactive oxygen species, and malondialdehyde) were examined before and after 16 weeks of training. As the results, body weight did not show any significant difference; however, body mass index, and % body fat were significantly difference in spinning group. The enhancement in physical fitness factors were recognized in both groups, which was greater in spinning group in sit-ups, back strength, and side steps. Blood parameters were significantly difference between groups, but between group and time interactions were significantly difference in glucose and reactive oxygen species. In conclusion, this study suggests that 16 weeks of bicycle exercises were positive changes in body composition, physical fitness and blood constituents, indicating that spinning cycle is more beneficial as compared to ordinary bicycle.

Low-Carbohydrate-High-Fat Diet: Can it Help Exercise Performance?

Low-carbohydrate-high-fat (LCHF) diets have been used as a means of weight loss and control of symptoms in several clinical conditions. There is emerging evidence that the metabolic changes induced by LCHF diets enhance endurance performance. The aims of this review are to examine the evidence of LCHF diets in improving various aspects of athletic performance. Long-term LCHF dietary intake may help control body weight and fat mass while maintaining lean body mass in athletes in weight-sensitive sports. LCHF-adapted endurance athletes can reach the maximal fat oxidation rate of approximately 1.5 g/min, with a lower carbohydrate oxidation rate and similar muscle glycogen content and a resynthesis rate compared to their counterparts consuming high-carbohydrate-low-fat (HCLF) diets. The elevated fat oxidation rate and glycogen sparing effect may improve performance in ultra-endurance events. These metabolic changes may also prevent the decline in performance in later stages of repeated high-intensity movements, in which the aerobic metabolism becomes more important. However, elevated blood concentrations of non-esterified fatty acids and ammonia during exercise after LCHF diets may lead to early development of central fatigue. It appears that at least several months of adaptation to a LCHF diet are required for the metabolic changes and restoration of muscle glycogen to occur. Further investigations on LCHF diets are needed regarding (1) performance after weight loss in weight-categorized sports; (2) repeated high-intensity exercise performance; (3) development of central fatigue during endurance events; (4) perceptual-motor performance during prolonged intermittent sports; and (5) ideal dietary fatty acid compositions.

Body Composition Changes After Very-Low-Calorie Ketogenic Diet in Obesity Evaluated by 3 Standardized Methods

CONTEXT

Common concerns when using low-calorie diets as a treatment for obesity are the reduction in fat-free mass, mostly muscular mass, that occurs together with the fat mass (FM) loss, and determining the best methodologies to evaluate body composition changes.

OBJECTIVE

This study aimed to evaluate the very-low-calorie ketogenic (VLCK) diet-induced changes in body composition of obese patients and to compare 3 different methodologies used to evaluate those changes.

DESIGN

Twenty obese patients followed a VLCK diet for 4 months. Body composition assessment was performed by dual-energy X-ray absorptiometry (DXA), multifrequency bioelectrical impedance (MF-BIA), and air displacement plethysmography (ADP) techniques. Muscular strength was also assessed. Measurements were performed at 4 points matched with the ketotic phases (basal, maximum ketosis, ketosis declining, and out of ketosis).

RESULTS

After 4 months the VLCK diet induced a -20.2 ± 4.5 kg weight loss, at expenses of reductions in fat mass (FM) of -16.5 ± 5.1 kg (DXA), -18.2 ± 5.8 kg (MF-BIA), and -17.7 ± 9.9 kg (ADP). A substantial decrease was also observed in the visceral FM. The mild but marked reduction in fat-free mass occurred at maximum ketosis, primarily as a result of changes in total body water, and was recovered thereafter. No changes in muscle strength were observed. A strong correlation was evidenced between the 3 methods of assessing body composition.

CONCLUSION

The VLCK diet-induced weight loss was mainly at the expense of FM and visceral mass; muscle mass and strength were preserved. Of the 3 body composition techniques used, the MF-BIA method seems more convenient in the clinical setting.

The Ketogenic Diet and Sport: A Possible Marriage?

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.), but the KD usually is not considered. Our hypothesis is that KD might be used to achieve fat loss without affecting strength/power performance negatively.