The Three-Month Effects of a Ketogenic Diet on Body Composition, Blood Parameters, and Performance Metrics in CrossFit Trainees: A Pilot Study

Abstract

Adopting low carbohydrate, ketogenic diets remains a controversial issue for individuals who resistance train given that this form of dieting has been speculated to reduce skeletal muscle glycogen levels and stifle muscle anabolism. We sought to characterize the effects of a 12-week ketogenic diet (KD) on body composition, metabolic, and performance parameters in participants who trained recreationally at a local CrossFit facility. Twelve participants (nine males and three females, 31 ± 2 years of age, 80.3 ± 5.1 kg body mass, 22.9 ± 2.3% body fat, 1.37 back squat: body mass ratio) were divided into a control group (CTL; n = 5) and a KD group (n = 7). KD participants were given dietary guidelines to follow over 12 weeks while CTL participants were instructed to continue their normal diet throughout the study, and all participants continued their CrossFit training routine for 12 weeks. Pre, 2.5-week, and 12-week anaerobic performance tests were conducted, and pre- and 12-week tests were performed for body composition using dual X-ray absorptiometry (DXA) and ultrasound, resting energy expenditure (REE), blood-serum health markers, and aerobic capacity. Additionally, blood beta hydroxybutyrate (BHB) levels were measured weekly. Blood BHB levels were 2.8- to 9.5-fold higher in KD versus CTL throughout confirming a state of nutritional ketosis. DXA fat mass decreased by 12.4% in KD (p = 0.053). DXA total lean body mass changes were not different between groups, although DXA dual-leg lean mass decreased in the KD group by 1.4% (p = 0.068), and vastus lateralis thickness values decreased in the KD group by ~8% (p = 0.065). Changes in fasting glucose, HDL cholesterol, and triglycerides were similar between groups, although LDL cholesterol increased ~35% in KD (p = 0.048). Between-group changes in REE, one-repetition maximum (1-RM) back squat, 400 m run times, and VO2peak were similar between groups. While our n-sizes were limited, these preliminary data suggest that adopting a ketogenic diet causes marked reductions in whole-body adiposity while not impacting performance measures in recreationally-trained CrossFit trainees. Whether decrements in dual-leg muscle mass and vastus lateralis thickness in KD participants were due to fluid shifts remain unresolved, and increased LDL-C in these individuals warrants further investigation.

Impact of a ketogenic diet intervention during radiotherapy on body composition: III. An interim analysis of the KETOCOMP study

“…This implies that KT would have increased the FFM-to-FM ratio in our patients, similar to our previous findings [16]. These findings are consistent with studies conducted in exercising individuals where short-term KDs resulted in FM loss while maintaining lean mass and performance [39–43]. Since most of our subjects did not exercise, a contribution of exercise-stimulated muscle protein synthesis can be ruled out asan explanation for the observed maintenance of SMM, and again the anti-catabolic effects of ketosis and/or anabolic effects of the supplemented essential amino acids may have contributed to the maintenance of SMM despite lower insulin levels and weight loss.…”

Effects of a ketogenic diet on body composition and strength in trained women

“…However, the KD group was instructed to consume foods ad libitum with a maximum of 50 g of carbohydrates per day, and reported decreasing energy intake bỹ 400 cal across the study period. More recently, Kephart et al [41] showed decreases in DXA-derived lower limb FFM and a decrease in vastus lateralis muscle thickness assessed by ultrasound when consuming a KD over a 12-week RT. The nutritional intervention of this study did not consider specific values of total calories or macronutrients used per g•kg − 1 •d − 1 , impairing the ability to estimate whether participants were in a state of energy deficiency or surplus.…”

Effects of a Ketogenic Diet on Muscle Fatigue in Healthy, Young, Normal-Weight Women: A Randomized Controlled Feeding Trial

“…In the area of exercise performance, there is a newfound interest in ketogenic diets. On one hand, ketogenic LCHF diets offer opportunities to induce weight loss and improve body composition, as reported recently [10][11][12]. This may increase relative, but not absolute, power due to decreased body weight, which can be important in situations when the ratio of lean to adipose body mass is crucial for performance.…”