Ketogenic diet benefits body composition and well-being but not performance in a pilot case study of New Zealand endurance athletes

Abstract

BackgroundLow-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.MethodsUsing a case study design, five New Zealand endurance athletes (4 females, 1 male) underwent a 10-week ketogenic dietary intervention. Body composition (sum of 8 skinfolds), performance indicators (time to exhaustion, VO2 max, peak power and ventilatory threshold), and gas exchange thresholds were measured at baseline and at 10 weeks. Mean change scores were calculated, and analysed using t-tests; Cohen’s effect sizes and 90% confidence limits were applied to quantify change. Individual interviews conducted at 5 weeks and a focus group at 10 weeks assessed athletes’ ketogenic diet experiences. Data was transcribed and analysed using thematic analysis.ResultsAll athletes increased their ability to utilise fat as a fuel source, including at higher exercise intensities. Mean body weight was reduced by 4 kg ± SD 3.1 (p = 0.046; effect size (ES):0.62), and sum of 8 skinfolds by 25.9 mm ± SD 6.9; ES: 1.27; p = 0.001). Mean time to exhaustion dropped by ~2 min (±SD 0.7; p = 0.004; ES: 0.53). Other performance outcomes showed mean reductions, with some increases or unchanged results in two individuals (VO2 Max: −1.69 ml.kg.min ± SD 3.4 (p = 0.63); peak power: -18 W ± SD 16.4 (p = 0.07), and VT2: -6 W ± SD 44.5 (p = 0.77). Athletes reported experiencing reduced energy levels initially, followed by a return of high levels thereafter, especially during exercise, but an inability to easily undertake high intense bouts. Each athlete reported experiencing enhanced well-being, included improved recovery, improvements in skin conditions and reduced inflammation.ConclusionsDespite performance decrements and some negative experiences, athletes were keen to pursue a modified low-carbohydrate, high-fat eating style moving forward due to the unexpected health benefits they experienced.Trial registrationACTRN: ACTRN12617000613303. Registered 28 April 2017, retrospectively registered.

Low Carb (LCD) and Ketogenic (KD) Diets Increase Quality of Life, Physical Performance, Body Composition and Metabolic Health of Women with Breast Cancer Better Than a Standard Diet (SD)

“…This is in accordance with published data from healthy subjects and athletes, which also performed well under LCD and KD regimes [18][19][20][21]. While some studies showed a negative impact when switching to LCDs or KDs on physical performance in the short term (21-30 days; [22]) and up to 10 weeks [23], the duration of 20 weeks in our study allowed the patients to adapt to the profound change in energy metabolism. Accordingly, at T20, none of the KD and LCD patients reported "lack of energy", and their physical performance was even superior to patients in the SD group.…”

Body composition and nutrition of female athletes

“…Therefore, it should be assumed that the daily energy expenditure of all studied subgroups was at a similar level. Hence, it should be concluded that the significantly lower BMI and fat content in subgroup C than in subgroups WL and TT demonstrated by the post hoc test are the expression of a different lifestyle of these women, including the wrong diet, which modified their body composition and weight [36]. The small amounts of energy ingredients supplied to the body in all subgroups, i.e.…”

Ketogenic Diet and Sport Performance

“…In an animal model, however, eight weeks of KD significantly enhanced the endurance capacity of C57/BL6 mice (Zinn et al, 2017); a correlation existed between body weight and running time until exhaustion with mice on heavier a KD running longer. This was attributed to keto-adaptation (Zinn et al, 2017). Since there was an inter-individual difference, the subjects possessing higher metabolic flexibility may prefer KD and reflect the weight change.…”

“…These results explain the partial mechanisms by which keto-adaption showed great potential in improving endurance exercise capacity. However, other researchers have reported that KD increased benefit in body composition and wellbeing but failed to enhance endurance capacity (Zinn, Wood, Williden, Chatterton, & Maunder, 2017).…”

“…Furthermore, a low-carbohydrate, high-fat diet impaired exercise economy and performance after intensified training in a group of elite race walkers (Burke et al, 2017). In an animal model, however, eight weeks of KD significantly enhanced the endurance capacity of C57/BL6 mice (Zinn et al, 2017); a correlation existed between body weight and running time until exhaustion with mice on heavier a KD running longer. This was attributed to keto-adaptation (Zinn et al, 2017).…”