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Grant M. Tinsley and Darryn S. Willoughby

Low-carbohydrate and very-low-carbohydrate diets are often used as weight-loss strategies by exercising individuals and athletes. Very-low-carbohydrate diets can lead to a state of ketosis, in which the concentration of blood ketones (acetoacetate, 3-β-hydroxybutyrate, and acetone) increases as a result of increased fatty acid breakdown and activity of ketogenic enzymes. A potential concern of these ketogenic diets, as with other weight-loss diets, is the potential loss of fat-free mass (e.g., skeletal muscle). On examination of the literature, the majority of studies report decreases in fat-free mass in individuals following a ketogenic diet. However, some confounding factors exist, such as the use of aggressive weight-loss diets and potential concerns with fat-free mass measurement. A limited number of studies have examined combining resistance training with ketogenic diets, and further research is needed to determine whether resistance training can effectively slow or stop the loss of fat-free mass typically seen in individuals following a ketogenic diet. Mechanisms underlying the effects of a ketogenic diet on fat-free mass and the results of implementing exercise interventions in combination with this diet should also be examined.

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Christopher C. Webster, Kathryn M. van Boom, Nur Armino, Kate Larmuth, Timothy D. Noakes, James A. Smith and Tertius A. Kohn

: 942051 doi:10.1016/0003-2697(76)90527-3 10.1016/0003-2697(76)90527-3 Bueno , N.B. , de Melo , I.S. , de Oliveira , S.L. , & da Rocha Ataide , T. ( 2013 ). Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: A meta-analysis of randomised controlled trials . The

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Iñigo Mujika

The aim of this case study was to report on the performance outcomes and subjective assessments of long-term low-carbohydrate, high-fat (LCHF) diet in a world-class long-distance triathlete who had been suffering from gastrointestinal distress in Ironman competition. The lacto-ovo vegetarian athlete (age = 39 years; height = 179 cm; usual racing body mass = 75 kg; sum of seven skinfolds = 36 mm) changed his usual high carbohydrate (CHO) availability diet to an LCHF diet for 32 weeks (∼95% compliance). He participated in three professional races while on the LCHF diet, but acutely restored CHO availability by consuming CHO in the preevent meals and during the race as advised. The athlete had his worst-ever half-Ironman performance after 21 weeks on the LCHF diet (18th). After 24 weeks on LCHF, he had his second worst-ever Ironman performance (14th) and suffered his usual gastrointestinal symptoms. He did not finish his third race after 32 weeks on LCHF. He regained his usual performance level within 5 weeks back on a high CHO diet, finishing second and fourth in two Ironman events separated by just 3 weeks. Subjective psychological well-being was very negative while on the LCHF diet, with feelings of depression, irritability, and bad mood. In conclusion, this long-term (32 weeks) LCHF intervention did not solve the gastrointestinal problems that the athlete had been experiencing, it was associated with negative performance outcomes in both the half-Ironman and Ironman competitions, and it had a negative impact on the athlete’s subjective well-being.

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Claire E. Badenhorst, Katherine E. Black and Wendy J. O’Brien

-CHO diet (78% CHO; 8.5 g/kg males and 8.0 g/kg females) or a low-CHO (80% fat and <50 g/day CHO) diet to emulate a ketogenic diet ( Volek, Noakes, & Phinney, 2015 ), while undergoing periodized training according to each individual’s training load. An accredited sport dietician designed individuals’ diets

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Trent Stellingwerff

Anecdotal claims have suggested that an increasing number of ultramarathoners purposely undertake chronic low-carbohydrate (CHO) ketogenic diets while training, and race with very low CHO intakes, as a way to maximize fat oxidation and improve performance. However, very little empirical evidence exists on specific fueling strategies that elite ultramarathoners undertake to maximize race performance. The study’s purpose was to characterize race nutrition habits of elite ultramarathon runners. Three veteran male ultrarunners (M ± SD; age 35 ± 2 years; mass 59.5 ± 1.7 kg; 16.7 ± 2.5 hr 100-mi. best times) agreed to complete a competition-specific nutrition intake questionnaire for 100-mi. races. Verbal and visual instructions were used to instruct the athletes on portion sizes and confirm dietary intake. Throughout 2014, the athletes competed in 16 ultramarathons with a total of 8 wins, including the prestigious Western States Endurance Run 100-miler (14.9 hr). The average prerace breakfast contained 70 ± 16 g CHO, 29 ± 20 g protein, and 21 ± 8 g fat. Athletes consumed an average of 1,162 ± 250 g of CHO (71 ± 20g/hr), with minor fat and protein intakes, resulting in caloric intakes totaling 5,530 ± 1,673 kcals (333 ± 105 kcals/hr) with 93% of calories coming from commercial products. Athletes also reported consuming 912 ± 322 mg of caffeine and 6.9 ± 2.4 g of sodium. Despite having limited professional nutritional input into their fueling approaches, all athletes practiced fueling strategies that maximize CHO intake and are congruent with contemporary evidence-based recommendations.

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, J Roche 4. Metabolic enzyme adaptations to long-term feeding of ketogenic diet containing medium-chain triglyceride in rats A Fukazawa, T Karasawa, Y Yokota, S Kondo, S Terada 5. Energy availability estimated in free-living conditions positively correlated with peak progesterone concentration in the

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Joanne G. Mirtschin, Sara F. Forbes, Louise E. Cato, Ida A. Heikura, Nicki Strobel, Rebecca Hall and Louise M. Burke

( Thomas et al., 2016 ) and evolving evidence around benefits of strategic training with low CHO availability ( Bartlett et al., 2015 ; Marquet et al., 2016 ). c. LCHF: 75–80% fat, 15–20% protein, and <50 g/day CHO. This is a ketogenic diet following the guidelines previously reported ( Volek & Phinney

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Amy J. Hector and Stuart M. Phillips

and FR groups. Finally, following a 30-day ketogenic diet (only 22 g carbohydrate per day), elite artistic gymnasts lost ∼1.9 kg fat mass, and a small but nonsignificant increase in LBM was observed, with no significant differences in strength tests ( Paoli et al., 2012 ). Thus, it is possible to

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Rachel McCormick, Alex Dreyer, Brian Dawson, Marc Sim, Leanne Lester, Carmel Goodman and Peter Peeling

– 2155 . PubMed ID: 31058762 doi:10.1249/MSS.0000000000002026 10.1249/MSS.0000000000002026 McKay , A.K. , Peeling , P. , Pyne , D.B. , Welvaert , M. , Tee , N. , Leckey , J.J. , & Burke , L.M. ( 2019 ). Chronic adherence to a ketogenic diet modifies iron metabolism in elite athletes

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Hunter S. Waldman, Brandon D. Shepherd, Brendan Egan and Matthew J. McAllister

implications of ketone bodies: The effects of ketone bodies in pathological conditions: Ketosis, ketogenic diet, redox states, insulin resistance, and mitochondrial metabolism . Prostaglandins, Leukotrienes & Essential Fatty Acids, 70 ( 3 ), 309 – 319 . doi:10.1016/j.plefa.2003.09.007 10.1016/j.plefa.2003