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Concept: Low-carbohydrate diet

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We investigated the effects of adaptation to a ketogenic low-carbohydrate (CHO), high-fat diet (LCHF) during 3 wk of intensified training on metabolism and performance of world-class endurance athletes. We controlled three isoenergetic diets in elite race walkers: High CHO availability (8.6 g.kg(-) 1.d(-1) CHO, 2.1 g.kg(-) 1.d(-1) protein; 1.2 g.kg(-) 1.d(-1) fat) consumed before/during/after training (HCHO, n = 9): identical macronutrient intake, periodised within/between days to alternate between low and high CHO availability (PCHO, n = 10); LCHF (<50 g.d(-1) CHO; 78% energy as fat; 2.1 g.kg(-) 1.d(-1) protein; LCHF, n = 10). Post-intervention, VO2 peak during race walking increased in all groups (P < 0.001, 90%CI: [2.55 - 5.20%]). LCHF was associated with markedly increased rates of whole-body fat oxidation, attaining peak rates of 1.57 ± 0.32 g.min(-1) during 2 h of walking at ∼80%VO2 peak. However, LCHF also increased the oxygen (O2 ) cost of race walking at velocities relevant to real-life race performance: O2 uptake (expressed as % of new VO2peak ) at a speed approximating 20 km race pace was reduced in HCHO and PCHO (90%CI:[-7.047;-2.55] and [-5.18;-0.86], respectively, but was maintained at pre-intervention levels in LCHF. HCHO and PCHO groups improved times for 10 km race walk: 6.6% (90% CI: [4.1; 9.1%]) and 5.3% [3.4; 7.2%], with no improvement (-1.6% [-8.5; 5.3%] for the LCHF group. In contrast to training with diets providing chronic or periodised high-CHO availability, and despite a significant improvement in VO2peak , adaptation to the topical LCHF diet negated performance benefits in elite endurance athletes, in part, due to reduced exercise economy. This article is protected by copyright. All rights reserved.

Concepts: Metabolism, Nutrition, Carbohydrate, Walking, Ketogenic diet, Low-carbohydrate diet, Ketosis, Racewalking

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Many successful ultra-endurance athletes have switched from a high-carbohydrate to a low-carbohydrate diet, but they have not previously been studied to determine the extent of metabolic adaptations.

Concepts: Nutrition, Obesity, Carbohydrate, Diets, Low-carbohydrate diet, Zone diet

95

Reduced calorie, low fat diet is currently recommended diet for overweight and obese adults. Prior data suggest that low carbohydrate diets may also be a viable option for those who are overweight and obese.

Concepts: Nutrition, Obesity, Carbohydrate, Diets, Diet food, Low-carbohydrate diet, Resistant starch, Low-fat

83

Low-carbohydrate diets are popular for weight loss, but their cardiovascular effects have not been well-studied, particularly in diverse populations.

Concepts: Nutrition, Randomized controlled trial, Low-carbohydrate diet

72

The present study aimed to test the association between high and low carbohydrate diets and obesity, and second, to test the link between total carbohydrate intake (as a percentage of total energy intake) and obesity.

Concepts: Metabolism, Nutrition, Energy, Obesity, Uranium, Carbohydrate, Food energy, Low-carbohydrate diet

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Folic acid fortification significantly reduced the prevalence of neural tube defects (NTDs) in the United States. The popularity of “low carb” diets raises concern that women who intentionally avoid carbohydrates, thereby consuming fewer fortified foods, may not have adequate dietary intake of folic acid.

Concepts: Photosynthesis, Nutrition, United States, Folic acid, Carbohydrate, Sugar, Gluconeogenesis, Low-carbohydrate diet

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(1) Background: Medical interventions including assisted reproductive technologies have improved fertility outcomes for many sub-fertile couples. Increasing research interest has investigated the effect of low carbohydrate diets, with or without energy restriction. We aimed to systematically review the published literature to determine the extent to which low carbohydrate diets can affect fertility outcomes; (2) Methods: The review protocol was registered prospectively with Prospective Register for Systematic Reviews (registration number CRD42016042669) and followed Preferred Reporting Items For Systematic Reviews and Meta-Analyses guidelines. Infertile women were the population of interest, the intervention was low carbohydrate diets (less than 45% total energy from carbohydrates), compared to usual diet (with or without co-treatments). Four databases were searched from date of commencement until April 2016; a supplementary Google scholar search was also undertaken. Title and abstract, then full text review, were undertaken independently and in duplicate. Reference lists of included studies and relevant systematic reviews were checked to ensure that all relevant studies were identified for inclusion. Quality assessment was undertaken independently by both authors using the Quality Criteria Checklist for Primary Research. Outcome measures were improved fertility outcomes defined by an improvement in reproductive hormones, ovulation rates and/or pregnancy rates; (3) Results: Seven studies fulfilled the inclusion criteria and were included in the evidence synthesis. Interventions were diverse and included a combination of low carbohydrate diets with energy deficit or other co-treatments. Study quality was rated as positive for six studies, suggesting a low risk of bias, with one study rated as neutral. Of the six studies which reported changes in reproductive hormones, five reported significant improvements post intervention; (4) Conclusion: The findings of these studies suggest that low carbohydrate diets warrant further research to determine their effect. These randomised controlled trials should consider the effect of carbohydrates (with or without energy deficit) on hormonal and fertility outcomes.

Concepts: Metabolism, Nutrition, Obesity, Randomized controlled trial, Infertility, Meta-analysis, Carbohydrate, Low-carbohydrate diet

39

Low-carbohydrate, high-fat and ketogenic diets are increasingly adopted by athletes for body composition and sports performance enhancements. However, as yet, there is no consensus on their efficacy in improving performance. There is also no comprehensive literature on athletes' experiences while undertaking this diet. The purpose of this pilot work was two-fold: i. to examine the effects of a non-calorie controlled ketogenic diet on body composition and performance outcomes of endurance athletes, and ii. to evaluate the athletes' experiences of the ketogenic diet during the 10-week intervention.

Concepts: Effectiveness, Case study, New Zealand, Ketogenic diet, Diets, Comprehensive examination, Low-carbohydrate diet, Ketosis

37

IBS is a debilitating condition that markedly affects quality of life. The chronic nature, high prevalence and associated comorbidities contribute to the considerable economic burden of IBS. The pathophysiology of IBS is not completely understood and evidence to guide management is variable. Interest in dietary intervention continues to grow rapidly. Ileostomy and MRI studies have demonstrated that some fermentable carbohydrates increase ileal luminal water content and breath hydrogen testing studies have demonstrated that some carbohydrates also increase colonic hydrogen production. The effects of fermentable carbohydrates on gastrointestinal symptoms have also been well described in blinded, controlled trials. Dietary restriction of fermentable carbohydrates (popularly termed the ‘low FODMAP diet’) has received considerable attention. An emerging body of research now demonstrates the efficacy of fermentable carbohydrate restriction in IBS; however, limitations still exist with this approach owing to a limited number of randomized trials, in part due to the fundamental difficulty of placebo control in dietary trials. Evidence also indicates that the diet can influence the gut microbiota and nutrient intake. Fermentable carbohydrate restriction in people with IBS is promising, but the effects on gastrointestinal health require further investigation.

Concepts: Oxygen, Gut flora, Nutrition, Randomized controlled trial, Digestive system, Placebo, Carbohydrate, Low-carbohydrate diet