Crisis of confidence averted: impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible

Probably not a substantial claim: may not pass S3 (load-bearing).

All dietary groups increased VO2peak at Adapt.

“All groups increased VO2peak (ml∙kg-1∙min-1) at Adapt (p = 0.02, 95%CI: [0.35–2.74]).”

May combine two claims.

Across HCHO and PCHO groups, blood glucose concentrations decreased across the training intervention such that values in the Adapt trials were lower than in the Baseline trial; however concentrations in the LCHF trial were increased.

“Across HCHO and PCHO groups, there was a decrease in blood glucose concentrations across the training intervention such that values in the Adapt trials were lower than in the Baseline trial (p<0.001); however concentrations in the LCHF trial were increased (p<0.001).”

Probably not a substantial claim: may not pass S3 (load-bearing).

At both testing times, the increase in exercise intensities across the stages of the economy test was associated with an increase in RER, VO2peak, HR and RPE.

“At both testing times, the increase in exercise intensities across the stages of the economy test was associated with an increase in RER (p<0.001), VO2peak (p<0.001), HR (p<0.001) and RPE (p<0.001) [Table 5].”

May combine two claims.

At the fourth stage of the economy test, there was a greater increase in the relative O2 cost of exercise (mL/kg/min) in the LCHF group in the Adapt trial, while this remained constant in the PCHO and HCHO groups.

“The pattern was repeated in the results from the fourth stage of the economy test: there was greater increase in the relative O2 cost of exercise (mL∙kg-1∙min-1) in the LCHF group in the Adapt trial (d = 0.84, p = 0.021), while this remained constant in the PCHO (p< 0.999) and HCHO group (p< 0.999).”

May combine two claims.

DXA-determined changes in body composition were small and similar between groups.

“DXA-determined changes in body composition were small and similar between groups (data reported by Bone et al., in review)”

• cites Bone et al., in reviewNot checked yet

  Not checked in the free run.

May combine two claims.

Blood glucose concentrations increased from baseline values during exercise, with an increase in exercise intensity being associated with high blood glucose concentrations.

“Blood glucose concentrations increased from baseline values during exercise, with an increase in exercise intensity being associated with high blood glucose concentrations (Stages 1, 2, 3 < 4, Max; p<0.001).”

May combine two claims.

At Adapt testing, absolute O2 cost values for the LCHF group were higher than for Baseline, while they were maintained at similar levels for the HCHO and PCHO groups.

“However, at Adapt testing, values for the LCHF group were higher than for Baseline (p< 0.001), while they were maintained at similar levels for HCHO and PCHO groups.”

Probably not a substantial claim: may not pass S3 (load-bearing).

When expressed in mL/kg/min, all groups achieved a significant increase in VO2peak over the Adapt phase.

“However, when combined with the small changes in BM and expressed in mL∙kg-1∙min-1, all groups achieved a significant increase over the Adapt phase: HCHO: 57.6 ± 4.6 to 58.3 ± 4.1; PCHO: 58.5 ± 3.2 to 59.9 ± 3.7; LCHF: 61.3 ± 5.1 to 63.6 ± 4.0; d = 0.36, p = 0.03).”

May combine two claims.

Rates of CHO oxidation were decreased and fat oxidation was increased in Adapt testing for the LCHF group, but remained similar for the HCHO and PCHO groups between tests.

“Rates of CHO oxidation were decreased and fat oxidation was increased in Adapt testing for the LCHF group (p<0.001), but remained similar for the HCHO and PCHO groups between tests.”

May combine two claims.

There were significant diet vs test interactions for RPE and HR, with the LCHF group displaying higher values in the Adapt trial.

“There were significant diet vs test interactions for RPE and HR, with the LCHF group displaying higher values in the Adapt trial (p< 0.001)”

May combine two claims.

Blood lactate concentrations increased as exercise intensity was increased across all dietary treatments, with similar patterns in both trials.

“Blood lactate concentrations increased as exercise intensity was increased across all dietary treatments (Stages 1, 2, 3 < 4, Max; p<0.001), with similar patterns in both trials.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The absolute O2 cost of exercise (L/min) increased across the four economy stages in all groups both at Baseline and Adapt testing.

“The absolute O2 cost of exercise (L∙min-1) increased across the four economy stages in all groups both at Baseline and Adapt testing [Table 5].”

May combine two claims.

The LCHF diet was associated with greater perception of effort and, on occasion, an inability to complete training sessions as planned.

“although LCHF was associated with greater perception of effort and, on occasion, an inability to complete sessions as planned.”

• cites [44] AKA McKay, 2019, The impact of chronic carbohydrate manipulation on mucosal immunity in elite endurance athletes, J Sports Sci sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Scale-determined changes in body mass over the Adapt phase showed a small but significant decrease in the LCHF group compared with the HCHO and PCHO groups.

“Scale determined changes in BM over the Adapt phase showed a small but significant decrease in the LCHF group compared with the other groups (0.9 ± 0.9, 1.2 ± 1.0; 2.7 ± 1.5 kg, p = 0.008 for HCHO, PCHO and LCHF respectively).”

May combine two claims.

At the second stage of the economy test, there was a significant increase in the relative O2 cost of exercise (mL/kg/min) in the LCHF group in the Adapt trial, while this remained similar in the PCHO and HCHO groups.

“At the second stage, there was a significant increase in the relative O2 cost of exercise (mL∙kg-1∙min-1) in the LCHF group in the Adapt trial (d = 0.81, p = 0.036), while this remained similar in the PCHO (p = 0.999) and HCHO group (p < 0.999).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Seven participants achieved a new personal best time at the 20 km race (4 from CHO/HCHO and 3 from LCHF/HCHO groups).

“7 participants achieved a new personal best time at the race (4 from CHO/HCHO and 3 from LCHF/HCHO) groups.”

May combine two claims.

The differences reached statistical significance for the HCHO group (race improvement by nearly 5%) and LCHF cohort (race impairment by ~2%).

“with the differences reaching statistical significance for the HCHO group (race improvement by nearly 5%) and LCHF cohort (race impairment by ~2%).”

May combine two claims.

Based on IAAF Points, the CHO/HCHO group performed better in Race 2 compared with Race 1 and maintained a similar performance level for the 20 km race.

“Comparison of these race performances based on IAAF Points (Fig 5C) showed that the CHO/HCHO group performed better in Race 2 compared with Race 1 and maintained a similar performance level for the 20 km race.”

May combine two claims.

Stool samples from the first study showed a significant reduction in Faecalibacterium species and an increase in Bacteroides and Dorea species.

“while stool samples showed a significant reduction in Faecalibacterium species and an increase in Bacteroides and Dorea species were increased [64].”

• cites [64] N Murtaza, 2019, The Effects of Dietary Pattern during Intensified Training on Stool Microbiota of Elite Race Walkers, Nutrients sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Blood β-hydroxybutyrate concentrations were low at pre- (~0.1 mmol/L) and post-race (~0.3 mmol/L) time points in all groups, apart from Race 2 in the LCHF group where they were higher than in the other groups at pre- (0.3 mmol/L) and post-race (0.6 mmol/L).

“Blood β-hydroxybutyrate concentrations were low at pre- (~0.1 mmol∙L-1) and post-race (~0.3 mmol∙L-1) time points in all groups, apart from Race 2 in the LCHF group where they were higher than in the other groups at pre- (0.3 mmol∙L-1) and post-race (0.6 mmol∙L-1).”

May combine two claims.

5 d of adaptation to a high fat diet reduced mitochondrial respiration supported by octanoylcarnitine and pyruvate as well as uncoupled respiration at rest, without change in the protein abundance of the complexes.

“Here, we found, via an in vitro substrate-uncoupler-inhibition-titration technique in permeabilised muscle fibres, that 5 d of adaptation to a high fat diet reduced mitochondrial respiration supported by octanoylcarnitine and pyruvate as well as uncoupled respiration at rest, without change in the protein abundance of the complexes [62].”

• cites [62] JJ Leckey, 2018, High dietary fat intake increases fat oxidation and reduces skeletal muscle mitochondrial respiration in trained humans, FASEB journalNot checked yet

  Not checked in the free run.

May combine two claims.

In the subgroup, the CHO/HCHO group showed a 2.3% improvement in 10,000 m Race 2 vs Race 1, while the LCHF/HCHO subgroup recorded a performance impairment of 3.5%.

“Comparison of performances in 10,000 m race walks in this cohort showed that they mirrored the outcomes of the larger group with the CHO/HCHO subgroup (n = 11) showing a 2.3% improvement in Race 2 (Adapt) vs Race 1 (Baseline) while the LCHF /HCHO subgroup recorded a performance change (impairment) of 3.5%”

May combine two claims.

CHO/HCHO improved from Race 1 to Race 2 with no further improvement to the 20 km race, whereas LCHF/HCHO recorded a significantly slower performance in Race 2, and their 20 km race was slower than would be predicted from Race 1.

“Comparison of these data for the three races showed that CHO/HCHO improved from Race 1 to Race 2 with no further improvement to the 20 km race, whereas the LCHF/HCHO recorded a significantly slower performance in Race 2, and their 20 km race was slower than would be predicted from Race 1 (p<0.01) [Fig 5B].”

Probably not a substantial claim: may not pass S3 (load-bearing).

Capillary blood samples collected pre-race and post-race showed a similar increase in blood glucose after the race (~10 mmol/L) compared with pre-race values (~5-6 mmol/L) in all groups and races.

“Capillary blood samples collected pre-race and post-race showed a similar increase in blood glucose after the race (~10 mmol∙L-1) compared with pre-race values (~5–6 mmol∙L-1) in all groups and races”

May combine two claims.

The LCHF/HCHO group commenced with a significantly higher performance for Race 1 than the other group, showed a decrease in performance in Race 2, but improved by the 20 km race such that their overall gain from Race 1 was similar to that achieved by the CHO/HCHO group.

“Meanwhile the LCHF/HCHO group commenced with a significantly higher performance for Race 1 than the other group (p = 0.011), showed a decrease in performance in Race 2 (p<0.001), but improved by the 20 km race such that their overall gain from Race 1 was similar to that achieved by the CHO/HCHO group.”

Classified as probably not a substantial claim.

The study was able to investigate and disprove a hypothesis based on anecdotal observations about successful performance in athletes.

“In addition, this study was able to investigate (and disprove) a hypothesis based on anecdotal observations about successful performance in athletes”

May combine two claims.

The LCHF group achieved an increase in aerobic capacity (ml∙kg-1∙min-1) and a greater reduction in BM than the other groups.

“Furthermore, the LCHF group achieved a training enhancement in the form of an increase in aerobic capacity (ml∙kg-1∙min-1) and a greater reduction in BM (presumably due to loss of muscle glycogen/water) than the other groups which should have reduced the energy cost of race walking.”

May combine two claims.

The changes seen in the first study were 7.5% and 6.2% for oxygen cost.

“This compares with values of 7.5% and 6.2% for the changes seen in the first study [4].”

• cites [4] LM Burke, 2017, Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers, J Physiol sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Interruption to training quality and perceptions of exertion were reported in the first 2 weeks of the LCHF treatment, but training effort and gross metrics were restored for the second half of the training camp.

“Although interruption to training quality and perceptions of exertion were reported in the first 2 weeks of the LCHF treatment, we noted that training effort and gross metrics (e.g. overall volume and the completion of key sessions) were restored for the second half of the training camp.”

May combine two claims.

Within the study conditions, 7 athletes achieved a personal best in the 20 km road race, with roughly equal numbers (4/11 and 3/9 from CHO/HCHO and LCHF/HCHO, respectively) achieving this outcome.

“It is worth noting that within our study conditions, 7 athletes achieved a personal best in the 20 km road race, with roughly equal numbers (4/11 and 3/9 from CHO/HCHO and LCHF/HCHO, respectively) achieving this outcome.”

May combine two claims.

The study reproduced the earlier finding of no superior performance outcome from periodised CHO availability above chronic high CHO availability; a lower magnitude of improvement was seen in both studies in the PCHO group.

“Again, we were able to reproduce the findings of our earlier study in failing to see a superior performance outcome from this periodised approach to CHO availability above that of the diet with chronic high CHO availability; indeed, a lower magnitude of improvement was seen in both studies in the PCHO group.”

May combine two claims.

Despite achieving substantial increases in the capacity for fat oxidation during intense exercise, 3.5 wk adaptation to a ketogenic low-CHO, high-fat diet reduced exercise economy and impaired performance of a real-life endurance event in elite athletes.

“The opportunity to replicate and extend the protocol of a previous small scale study provides confidence that our findings were robust: despite achieving substantial increases in the capacity for fat oxidation during intense exercise, 3.5 wk adaptation to a ketogenic low-CHO, high-fat diet reduced exercise economy and impaired performance of a real-life endurance event in elite athletes.”

Classified as probably not a substantial claim.

Despite remarkable increases in rates of fat oxidation during exercise of varying intensities, translation to improved endurance performance has not been clearly demonstrated.

“Despite remarkable increases in rates of fat oxidation during exercise of varying intensities, the translation to improved endurance performance has not been clearly demonstrated [9, 16].”

• cites [9] LM Burke, 2020, Ketogenic low CHO, high fat diet: the future of elite endurance sport, J PhysiolNot checked yet

  Not checked in the free run.

• cites [16] LM Burke, 2006, "Fat adaptation" for athletic performance: the nail in the coffin?, J Appl Physiol sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

In the previous study, there was a non-significant improvement of 5.3% for HCHO.

“with a non-significant improvement of 5.3% for HCHO”

• cites [4] LM Burke, 2017, Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers, J Physiol sourceNot checked yet

  Not checked in the free run.

May combine two claims.

In the previous study, O2 uptake at a speed approximating 20 km race pace, expressed as % of new VO2peak, was reduced in HCHO and PCHO but maintained at pre-intervention levels in LCHF.

“O2 uptake at a speed approximating 20 km race pace, expressed as % of new VO2peak, was reduced in HCHO and PCHO but maintained at pre-intervention levels in LCHF.”

• cites [4] LM Burke, 2017, Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers, J Physiol sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

CHO restriction with a high fat intake upregulates the release, transport, uptake and oxidation of fat in muscle, even in endurance athletes whose training has already promoted such adaptations.

“Indeed, it has long been known that CHO restriction in concert with a high fat intake upregulates the release, transport, uptake and oxidation of fat in the muscle, even in endurance athletes whose training has already promoted such adaptations [8, 9].”

• cites [8] LL Spriet, 2014, New insights into the interaction of carbohydrate and fat metabolism during exercise, Sports Med sourceNot checked yet

  Not checked in the free run.

• cites [9] LM Burke, 2020, Ketogenic low CHO, high fat diet: the future of elite endurance sport, J PhysiolNot checked yet

  Not checked in the free run.

May combine two claims.

Energy availability was preserved and standardised such that it did not interfere with training adaptations or favour one group over another.

“suggesting that energy availability was preserved and standardised such that it did not interfere with training adaptations or favour one group over another.”

Probably not a substantial claim: may not pass S4 (based).

A 10,000 m race walk is not limited by glycogen depletion as might occur in marathons or 50 km race walk.

“Although a 10,000 m race walk is not limited by glycogen depletion as might occur in the marathons/50 km race walk, it has other points of direct relevance to these longer races.”

Classified as probably not a substantial claim.

Previous studies of specialist distance runners have found that 10-km personal best time is a good predictor of marathon performance.

“Furthermore, previous studies of specialist distance runners have found that 10-km personal best time is a good predictor of marathon performance [29]”

• cites [29] TD Noakes, 1990, Peak treadmill running velocity during the VO2 max test predicts running performance, J Sports Sci sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

One participant from the PCHO group experienced an injury which prevented him from competing in the second 10,000 m race.

“One participant from the PCHO group experienced an injury which prevented him from competing in the second race.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The study was approved by the Ethics Committee of the Australian Institute of Sport and registered with the Australian and New Zealand Clinical Trials Registry.

“This study, conforming to the Declaration of Helsinki, was approved by the Ethics Committee of the Australian Institute of Sport (AIS, #20161201) and registered with the Australian and New Zealand Clinical Trials Registry (ACTRN12619000794101).”

Classified as probably not a substantial claim. May combine two claims.

Robust retooling of muscle to increase fat oxidation occurs in 5 d, with no further enhancement after this period.

“The initial study was planned in view of pre-existing data that robust retooling of muscle to increase fat oxidation occurs in 5 d, with no further enhancement after this period [12]”

• cites [12] JH Goedecke, 1999, Metabolic adaptations to a high-fat diet in endurance cyclists, Metabolism sourceNot checked yet

  Not checked in the free run.

Classified as probably not a substantial claim. May combine two claims.

The previous study concluded that adaptation to the LCHF diet negated performance benefits in elite endurance athletes, despite an increase in aerobic capacity, attributed in part to reduced exercise economy.

“We concluded that adaptation to the LCHF diet negated performance benefits in elite endurance athletes, despite an increase in aerobic capacity, which we attributed in part to reduced exercise economy [4].”

• cites [4] LM Burke, 2017, Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers, J Physiol sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

To counter individual differences in the accuracy of portable analyzers, each participant was assigned to a specific device for the duration of the study.

“To counter for any individual differences in the accuracy of these portable analyzers, each participant was assigned to a specific device for the duration of their involvement in the study.”

Classified as probably not a substantial claim.

Residual baseline differences between groups were noted and included in the statistical analyses.

“Nevertheless, since many higher ranked 50 km race specialists chose the LCHF diet, residual baseline differences between groups were noted and included in the statistical analyses.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The race was undertaken on the same day by all athletes, and participation in the other testing sessions was rotated with the order and conditions standardised for each participant.

“although the race was undertaken on the same day by all athletes, participation in the other testing sessions was rotated with the order and conditions being standardised for each participant.”

Classified as probably not a substantial claim.

Matching participants according to their beliefs reduces the known performance bias due to placebo and nocebo effects.

“This methodology should be continued in the replication study since matching participants according to their beliefs will reduce the known performance bias due to placebo and nocebo effects [21].”

• cites [21] E Carlino, 2014, The effects of placebos and nocebos on physical performance, Handb Exp Pharmacol sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

An a priori sample size of 10 participants per treatment group was established with the goal of having 8 participants complete each study component.

“Based on the experience from our first study [4], we established an a priori sample size of 10 participants per treatment group with the goal of having 8 participants complete each of the study components.”

• cites [4] LM Burke, 2017, Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers, J Physiol sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

All participants provided informed consent after receiving comprehensive oral and written details of the protocol.

“All participants provided informed consent after receiving comprehensive oral and written details of the protocol.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Six mandatory training sessions were undertaken under standardised conditions with external monitoring.

“Table 2 details the weekly program, noting six mandatory sessions that were undertaken under standardised conditions with external monitoring.”

May combine two claims.

Analysis showed that micronutrient content of the diet typically met dietary reference intakes, although it was lower than that of the higher CHO diets due to fundamental restrictions on intake of many nutrient-rich foods.

“including analysis that micronutrient content of diet typically met dietary reference intakes, although it was lower than that of the higher CHO diets due to fundamental restrictions on intake of many nutrient-rich foods [23]”

• cites [23] JG Mirtschin, 2018, Organisation of Dietary Control for Nutrition-Training Intervention Involving Periodized Carbohydrate (CHO) Availability and Ketogenic Low CHO High Fat (LCHF) Diet, Int J Sport Nutr Exerc Metab sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

Compliance to the dietary prescription and reporting requirements was checked daily.

“Compliance to the dietary prescription and reporting requirements was checked daily.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Much of the information about longer exposure to LCHF is provided by social media commentary rather than rigorous examination of the time course of adaptation.

“However, much of this information is provided by social media commentary rather than rigorous examination of the time course of adaptation [25].”

• cites [25] LM Burke, Ketogenic Low CHO, High Fat diet: the future of elite endurance sport?, J Physiol. In pressNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The study took place at the Australian Institute of Sport with participants living in athlete residences and undertaking all meals and training sessions under supervision during the first two phases.

“The study took place at the Australian Institute of Sport (AIS) with participants living in athlete residences and undertaking all meals and training sessions under supervision during the first two phases.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The training camp effect, whereby performance is enhanced simply due to an increased training load, high-level training partners and enhanced support/resources, is well known.

“The “training camp effect” [31] whereby performance is enhanced simply due to an increased training load, high-level training partners and enhanced support/resources is well known”

• cites [31] PU Saunders, 2010, An attempt to quantify the placebo effect from a three-week simulated altitude training camp in elite race walkers, Int J Sports Physiol Perform sourceNot checked yet

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Classified as probably not a substantial claim.

After removing two participants, 26 data sets from participants who completed the requirements of the 5.5-wk training study were analysed.

“These walkers were removed from the current analysis, leaving 26 data sets from participants who completed the requirements of the 5.5-wk training study.”

Classified as probably not a substantial claim.

Initial fatigue and reduced exercise capacity is well reversed by 4 wk.

“while initial fatigue and reduced exercise capacity is well reversed by 4 wk [10].”

• cites [10] SD Phinney, 1983, The human metabolic response to chronic ketosis without caloric restrictions: Preservation of submaximal exercise capacity with reduced carbohydrate oxidation, Metabolism sourceNot checked yet

  Not checked in the free run.

Classified as probably not a substantial claim. May combine two claims.

The VO2peak and walking economy test was undertaken in an overnight fasted, rested state.

“This test was undertaken in an overnight fasted, rested state.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Training sessions were undertaken as a group and were monitored by the research team as well as recorded by participants in a daily log.

“Training sessions were undertaken as a group and were monitored by the research team as well as recorded by participants in a daily log.”

May combine two claims.

Menus deliberately maximised the inclusion of unprocessed/nutrient-rich foods within the strict macronutrient specifications of the LCHF and were consumed by participants under rigorous control.

“Menus deliberately maximised the inclusion of unprocessed/nutrient-rich foods within the strict macronutrient specifications of the LCHF and were consumed by participants under rigorous control.”

May combine two claims.

Participants were compliant with their assigned dietary treatment and the monitoring of their food intake and training sessions.

“Participants were compliant with their assigned dietary treatment and the monitoring of their food intake and training sessions.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

This systematic error does not change the assessment of the oxygen cost of exercise.

“Although this could be seen as a systematic error that does not change the assessment of the oxygen cost of exercise”

• AssumptionThe authors state this as an assumption: The contribution of ketone bodies to substrate use does not change the assessment of the oxygen cost of exercise.

Probably not a substantial claim: may not pass S3 (load-bearing).

The inclusion of female participants adds to the ecological validity of the study.

“The inclusion of female participants was a deliberate element of the new study; this adds to the ecological validity of the study”

Classified as probably not a substantial claim.

Interruption to colonies of nitrate/nitrite reducing bacteria in the mouth due to the use of oral mouthwashes disrupts the production of Nitric Oxide (NO) from dietary nitrate via the entero-salivary pathway, causing functional endpoints such as an increase in blood pressure.

“Furthermore, interruption to colonies of nitrate/nitrate reducing bacterial in the mouth due to the use of oral mouthwashes has been shown to disrupt the production of Nitric Oxide (NO) from dietary nitrate via the entero-salivary pathway, causing functional endpoints (e.g., increase in blood pressure) [65].”

• cites [65] J Petersson, 2009, Gastroprotective and blood pressure lowering effects of dietary nitrate are abolished by an antiseptic mouthwash, Free Radic Biol Med sourceNot checked yet

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May combine two claims.

Rates of fat oxidation during exercise of varying speeds/intensities were substantially increased by exposure to the LCHF diet, with an associated increase in the oxygen cost of such exercise (i.e., reduced economy).

“rates of fat oxidation during exercise of varying speeds/intensities were substantially increased by exposure to the LCHF diet, with an associated increase in the oxygen cost of such exercise (i.e., reduced economy) as predicted from the stochiometry of fat and CHO oxidation pathways”

May combine two claims.

Training and racing while consuming diets providing periodic or sustained high CHO availability improved real-world endurance performance in contrast to the performance decrement on a LCHF diet.

“Training and racing while consuming diets providing periodic or sustained high CHO availability improved real-world endurance performance in contrast to the performance decrement on a LCHF diet”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Increased rates of fat oxidation during exercise are a hallmark of endurance training and offer the advantage of making better use of a fuel substrate found in relatively unlimited amounts in even the leanest endurance athlete.

“Increased rates of fat oxidation during exercise are a hallmark of endurance training and offer the advantage of making better use of a fuel substrate found in relatively unlimited amounts in even the leanest endurance athlete [25].”

• cites [25] LM Burke, Ketogenic Low CHO, High Fat diet: the future of elite endurance sport?, J Physiol. In pressNot checked yet

  Not checked in the free run.

May combine two claims.

The inclusion of female participants created a risk of diluted findings due to the greater numerical spread of the data and the potential for females to have a different response due to true sex differences or a confounding effect of menstrual status.

“but created a risk of diluted findings due to the greater numerical spread of the data (e.g., female athletes have lower values for aerobic capacity and speed), as well as the potential for females to have a different response due to true sex differences or a confounding effect of menstrual status on important variables.”

May combine two claims.

Deriving adenosine triphosphate (ATP) from fat rather than CHO fuels has a higher oxygen cost, which can be explained by the stoichiometry of oxidative phosphorylation from different substrates.

“Empirically derived data from over a century ago [57, 58] or more recently [59] have demonstrated the higher oxygen cost of deriving adenosine triphosphate (ATP) from fat rather than CHO fuels; this can be explained by an appreciation of the stoichiometry of oxidative phosphorylation from different substrates [60].”

• cites [57] Zuntz N, Schaumburg W. Studien zu einer Physiologie des Marsches. Berlin, 1901, pp. 361-Not checked yet

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• cites [58] A Krogh, 1920, The Relative Value of Fat and Carbohydrate as Sources of Muscular Energy: With Appendices on the Correlation between Standard Metabolism and the Respiratory Quotient during Rest and Work, Biochem J sourceNot checked yet

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• cites [59] M Cole, 2014, Improved gross efficiency during long duration submaximal cycling following a short-term high carbohydrate diet, Int J Sports MedNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

A capacity for high rates of fat oxidation in fasted but non-adapted athletes in a Fatmax test may correlate with race performance in ultra-endurance triathletes.

“Furthermore, we appreciate that a capacity for high rates of fat oxidation in fasted but non-adapted athletes in a Fatmax test may correlate with race performance, as has been recently reported in ultra-endurance triathletes [54].”

• cites [54] J Frandsen, 2017, Maximal Fat Oxidation is Related to Performance in an Ironman Triathlon, Int J Sports Med sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

In some populations, enhancements in training status might lead to an increase in muscle oxidation of ketone bodies leading to a greater underestimation of their contribution in the post-intervention phase.

“we acknowledge that in some populations, enhancements in training status might lead to an increase in muscle oxidation of ketone bodies leading to a greater underestimation of their contribution in the post-intervention phase [56].”

• cites [56] M Evans, 2017, Metabolism of ketone bodies during exercise and training: physiological basis for exogenous supplementation, J Physiol sourceNot checked yet

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Classified as probably not a substantial claim. May combine two claims.

The main characteristics of successful endurance athletes are a high aerobic capacity, the ability to sustain exercise for long periods at a high percentage of this, and high economy of movement.

“Whatever the underlying cause of the increased oxygen cost of exercise, we note that the main characteristics of successful endurance athletes are a high aerobic capacity, the ability to sustain exercise for long periods at a high percentage of this, and high economy of movement [44, 67].”

• cites [44] AKA McKay, 2019, The impact of chronic carbohydrate manipulation on mucosal immunity in elite endurance athletes, J Sports Sci sourceNot checked yet

  Not checked in the free run.

• cites [67] MJ Joyner, 2007, Endurance exercise performance: the physiology of champions, J Physiol sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

The current study did not allow the interrogation of muscle substrate kinetics or mechanisms underpinning the changes in fuel use during exercise.

“The current study did not allow the interrogation of muscle substrate kinetics or mechanisms underpinning the changes in fuel use during exercise.”

Classified as probably not a substantial claim. May combine two claims.

All athletes competed in the same two races under the same environmental and external factors, and with equal psychological investment in their preceding treatment.

“One advantage of the new protocol involving a single training camp was that all athletes competed in the same two races under the same environmental and external factors, and with equal psychological investment in their preceding treatment.”

• AssumptionRests on an assumption: The prize money correction (5% allowance to LCHF participants) ensured that all participants were optimally motivated to race as hard as possible in each race.

Classified as probably not a substantial claim. May combine two claims.

Exercise economy in athletes is important in determining performance and discriminating between successful athletes.

“Indeed, both modelling [68] and measures [69] of exercise economy in athletes show its importance in determining performance and discriminating between successful athletes [70].”

• cites [68] S Kipp, 2019, Extrapolating Metabolic Savings in Running: Implications for Performance Predictions, Front Physiol sourceNot checked yet

  Not checked in the free run.

• cites [69] J Daniels, 1992, Running economy of elite male and elite female runners, Med Sci Sports Exerc sourceNot checked yet

  Not checked in the free run.

• cites [70] HB Larsen, 2003, Kenyan dominance in distance running, Comp Biochem Physiol A Mol Integr Physiol sourceNot checked yet

  Not checked in the free run.

May combine two claims.

The performance differences are robust and highly meaningful to the outcomes of real life sporting events.

“These performance differences are robust and highly meaningful to the outcomes of real life sporting events.”

May combine two claims.

The study approaches an independent direct replication design due to the significant number of new personnel and new participants including females, or allocation to new treatments.

“We consider our study to approach an independent direct replication design, due to the significant number of new personnel within the research team, and the involvement of new (19/26) participants including females within the cohort of elite race walkers, or allocation to new treatments (3/7, with 2, 1 and 1 participants electing to repeat their previous intervention with LCHF, PCHO and HCHO diets”

Classified as probably not a substantial claim.

A key rationale for the uptake of the LCHF diet by endurance athletes is a substantial increase in the capacity to oxidise fat as a muscle substrate across an increased range of exercise intensities.

“A key rationale for the uptake of the LCHF diet by endurance athletes is a substantial increase in the capacity to oxidise fat as a muscle substrate across an increased range of exercise intensities [5, 6, 26, 27].”

• cites [5] JS Volek, 2015, Rethinking fat as a fuel for endurance exercise, Eur J Sport Sci sourceNot checked yet

  Not checked in the free run.

• cites [6] T Noakes, 2014, Low-carbohydrate diets for athletes: what evidence?, Br J Sports Med sourceNot checked yet

  Not checked in the free run.

• cites [26] JS Volek, 2016, Metabolic characteristics of keto-adapted ultra-endurance runners, Metabolism sourceNot checked yet

  Not checked in the free run.

• cites [27] CC Webster, 2016, Gluconeogenesis during endurance exercise in cyclists habituated to a long-term low carbohydrate high-fat diet, J Physiol sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Another group who studied 31 d of LCHF in endurance-trained runners confirmed the findings of impaired exercise economy, but noted that this effect was amplified at intensities above 70% VO2max and was of greater magnitude than could be explained by stoichiometric calculations.

“Indeed, another group who studied 31 d of LCHF in endurance-trained runners confirmed our findings of impaired exercise economy, but noted that this effect was amplified at intensities above 70% VO2max and was of greater magnitude than could be explained by stoichiometric calculations [61].”

• cites [61] DM Shaw, 2019, Effect of a Ketogenic Diet on Submaximal Exercise Capacity and Efficiency in Runners, Med Sci Sports Exerc sourceNot checked yet

  Not checked in the free run.

Classified as probably not a substantial claim.

The study design (a single training camp) prevented controlling or standardizing the phase of the menstrual cycle other than noting that the protocol created a period of ~3.5 wk between Baseline and Adapt testing, and therefore the likelihood of it falling during a similar menstrual phase within each female participant.

“The study design (a single training camp) prevented us from controlling or standardizing the phase of the menstrual cycle other than noting that the protocol created a period of ~3.5 wk between the Baseline and Adapt testing, and therefore the likelihood of it falling during a similar menstrual phase within each female participant.”

• AssumptionRests on an assumption: The phase of the menstrual cycle did not confound the comparison of dietary treatments in female participants.

May combine two claims.

The low participant numbers, non-randomised allocation, confounding camp effect, and loss of one female from the LCHF treatment preclude any meaningful discussion of sex-specific responses to the treatment.

“The low participant numbers, the non-randomised allocation of the dietary treatments, the confounding “camp effect” of chronically training with partners of superior ability, and the loss of one of the two females from the LCHF treatment precludes any meaningful discussion of sex-specific responses to the treatment.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The time lag between upregulation of fat oxidation and the abatement of fatigue has been previously reported.

“This time lag between upregulation of fat oxidation and the abatement of fatigue has been previously reported [10].”

• cites [10] SD Phinney, 1983, The human metabolic response to chronic ketosis without caloric restrictions: Preservation of submaximal exercise capacity with reduced carbohydrate oxidation, Metabolism sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Compared to his habitual diet, the introduction of exogenous CHO intake to performance trials, in conjunction with practice in training, was associated with meaningful (2.8% and 1.6%) improvements in a 20 km cycling time trial and a 4-min power test, respectively, while changes in 30 s sprint and 100 km time trial were judged to be trivial.

“Compared to his habitual diet, the introduction of exogenous CHO intake to performance trials, in conjunction with practice in training, was associated with meaningful (2.8% and 1.6%) improvements in a 20 km cycling time trial and a 4-min power test, respectively, while changes in 30 s sprint and 100 km time trial were judged to be trivial [70].”

• cites [70] HB Larsen, 2003, Kenyan dominance in distance running, Comp Biochem Physiol A Mol Integr Physiol sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Supplementation with exogenous ketone products to achieve similarly high levels has been shown to alter metabolism and enhance performance in one study, although this has been a singular finding.

“For example, supplementation with exogenous ketone products to achieve similarly high levels has been shown to alter metabolism and enhance performance in one study [76], although this has been a singular fining [77–80].”

• cites [76] PJ Cox, 2016, Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes, Cell Metab sourceNot checked yet

  Not checked in the free run.

• cites [77] JJ Leckey, 2017, Ketone Diester Ingestion Impairs Time-Trial Performance in Professional Cyclists, Front Physiol sourceNot checked yet

  Not checked in the free run.

• cites [78] BE Scott, 2018, The effect of 1,3-butanediol and carbohydrate supplementation on running performance, J Sci Med SportNot checked yet

  Not checked in the free run.

• cites [79] M Evans, 2018, Intermittent Running and Cognitive Performance after Ketone Ester Ingestion, Med Sci Sports Exerc sourceNot checked yet

  Not checked in the free run.

• cites [80] M Evans, 2019, No Benefit of Ingestion of a Ketone Monoester Supplement on 10-km Running Performance, Med Sci Sports Exerc sourceNot checked yet

  Not checked in the free run.

May combine two claims.

Athletes adapted to a high fat diet must exercise at a higher percentage of their aerobic capacity and at a higher heart rate to achieve the same speed or power outputs, or accept a lower output when working at the same fraction of their aerobic or cardiovascular capacity.

“athletes must exercise at a higher percentage of their aerobic capacity and at a higher heart rate to achieve the same speed or power outputs, or accept a lower output when working at the same fraction of their aerobic or cardiovascular capacity.”

Classified as probably not a substantial claim. May combine two claims.

The LCHF group's increase in aerobic capacity and greater reduction in BM should have reduced the energy cost of race walking.

“which should have reduced the energy cost of race walking.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The value of specific strategies of periodization of CHO availability in promoting greater training adaptations in elite athletes remains unclear.

“The value of specific strategies of periodization of CHO availability in promoting greater training adaptations in elite athletes also remains unclear.”

Probably not a substantial claim: may not pass S3 (load-bearing).

A recent case history detailed a highly competitive triathlete who incorporated 8 sessions in which CHO (60 g∙h-1) was consumed during high intensity training sessions (2∙wk-1) into his long-term (>2 y) LCHF diet.

“For example, a recent case history [75] detailed the experiences of a highly competitive triathlete who incorporated 8 sessions in which CHO (60 g∙h-1) was consumed during high intensity training sessions (2∙wk-1) to his long-term (> 2 y) LCHF diet.”

• cites [75] CC Webster, 2018, A Carbohydrate Ingestion Intervention in an Elite Athlete Who Follows a Low-Carbohydrate High-Fat Diet, Int J Sports Physiol Perform sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S3 (load-bearing).

New shoe technology achieves a 4% mean reduction in the oxygen cost of running.

“which achieves a 4% mean reduction in the oxygen cost of running [72].”

• cites [72] W Hoogkamer, 2018, A Comparison of the Energetic Cost of Running in Marathon Racing Shoes, Sports Med sourceNot checked yet

  Not checked in the free run.

May combine two claims.

The failure of the LCHF group to achieve a performance improvement is at least partially explained by decreased speed at their highest sustainable fraction of aerobic capacity, due to lower economy of fat oxidation and known impairment of muscle glycogen oxidation.

“However, this provides further evidence that their failure to achieve a performance improvement is at least partially explained by the decreased speed hypothesised to occur at their highest sustainable fraction of aerobic capacity, due to the lower economy of fat oxidation and the known impairment of muscle glycogen oxidation [73].”

• cites [73] T Stellingwerff, 2006, Decreased PDH activation and glycogenolysis during exercise following fat adaptation with carbohydrate restoration, Am J Physiol Endocrinol Metab sourceNot checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S4 (based).

The increase in fat oxidation associated with keto-adaptation increases the oxygen cost of movement at any given speed.

“According to our model, the increase in fat oxidation associated with keto-adaptation increases the oxygen cost of movement at any given speed and, we postulate, reduces the speed or power achieved at any given percentage of maximal aerobic capacity.”

May combine two claims.

The protocol exceeded the period shown by several different laboratories to achieve robust cellular retooling to maximise rates of muscle fat oxidation, as well as achieve training-associated performance changes.

“However, as detailed in Table 1, our protocol exceeded the period shown by several different laboratories [12–15] to achieve robust cellular retooling to maximise rates of muscle fat oxidation, as well as achieve training-associated performance changes [30].”

• cites [12] JH Goedecke, 1999, Metabolic adaptations to a high-fat diet in endurance cyclists, Metabolism sourceNot checked yet

  Not checked in the free run.

• cites [13] LM Burke, 2000, Effect of fat adaptation and carbohydrate restoration on metabolism and performance during prolonged cycling, J Appl Physiol sourceNot checked yet

  Not checked in the free run.

• cites [14] LM Burke, 2002, Adaptations to short-term high-fat diet persist during exercise despite high carbohydrate availability, Med Sci Sports Exerc sourceNot checked yet

  Not checked in the free run.

• cites [15] L Havemann, 2006, Fat adaptation followed by carbohydrate loading compromises high-intensity sprint performance, J Appl Physiol sourceNot checked yet

  Not checked in the free run.

• cites [30] Ewing L. Racewalker Evan Dunfee’s high-fat diet: ‘You get used to eating packets of butter’. https://www.theglobeandmail.com/sports/olympics/racewalker-evan-dunfees-high-fat-diet-you-get-used-to-eating-packets-of-butter/article33876222/ Cited July 1, 2019.Not checked yet

  Not checked in the free run.

Probably not a substantial claim: may not pass S4 (based).

The increase in fat oxidation associated with keto-adaptation reduces the speed or power achieved at any given percentage of maximal aerobic capacity.

“According to our model, the increase in fat oxidation associated with keto-adaptation increases the oxygen cost of movement at any given speed and, we postulate, reduces the speed or power achieved at any given percentage of maximal aerobic capacity.”