Abstract
BackgroundDespite the increasing use of very low carbohydrate ketogenic diets (VLCKD) in weight control and management of the metabolic syndrome there is a paucity of research about effects of VLCKD on sport performance. Ketogenic diets may be useful in sports that include weight class divisions and the aim of our study was to investigate the influence of VLCKD on explosive strength performance.Methods8 athletes, elite artistic gymnasts (age 20.9 ± 5.5 yrs) were recruited. We analyzed body composition and various performance aspects (hanging straight leg raise, ground push up, parallel bar dips, pull up, squat jump, countermovement jump, 30 sec continuous jumps) before and after 30 days of a modified ketogenic diet. The diet was based on green vegetables, olive oil, fish and meat plus dishes composed of high quality protein and virtually zero carbohydrates, but which mimicked their taste, with the addition of some herbal extracts. During the VLCKD the athletes performed the normal training program. After three months the same protocol, tests were performed before and after 30 days of the athletes’ usual diet (a typically western diet, WD). A one-way Anova for repeated measurements was used.ResultsNo significant differences were detected between VLCKD and WD in all strength tests. Significant differences were found in body weight and body composition: after VLCKD there was a decrease in body weight (from 69.6 ± 7.3 Kg to 68.0 ± 7.5 Kg) and fat mass (from 5.3 ± 1.3 Kg to 3.4 ± 0.8 Kg p < 0.001) with a non-significant increase in muscle mass.ConclusionsDespite concerns of coaches and doctors about the possible detrimental effects of low carbohydrate diets on athletic performance and the well known importance of carbohydrates there are no data about VLCKD and strength performance. The undeniable and sudden effect of VLCKD on fat loss may be useful for those athletes who compete in sports based on weight class. We have demonstrated that using VLCKD for a relatively short time period (i.e. 30 days) can decrease body weight and body fat without negative effects on strength performance in high level athletes.
Highlights
Despite the increasing use of very low carbohydrate ketogenic diets (VLCKD) in weight control and management of the metabolic syndrome there is a paucity of research about effects of VLCKD on sport performance
Kreider and colleagues studied the effect of a specific exercise program in overweight woman with a VLCKD or normal carbohydrate content diet [17], but only few papers that focus on the influence of VLCKD on sports performance have been published, and with conflicting results: showing benefits [18,19], no effect [20,21] or impairment [22,23]
Procedures for body weight reduction that are in very widespread use by athletes, especially those competing in sports with weight categories, only few studies examining VLCKD and exercise have been published
Summary
Despite the increasing use of very low carbohydrate ketogenic diets (VLCKD) in weight control and management of the metabolic syndrome there is a paucity of research about effects of VLCKD on sport performance. The physiological function of ketosis is to supply the heart and central nervous system (CNS) with a high energy metabolic substrate during reduced glucose availability – by this mechanism ketones allowed our ancestors to survive and remain efficient even when deprived of food [8,9] On this basis the ketosis induced by a VLCKD may be defined as “physiological ketosis” to distinguish it from the severe pathological ketosis (or ketoacidosis) commonly seen in uncontrolled diabetes [10,11,12]. In the last few years though an increasing amount of evidence has accumulated concerning the positive effects on short term weight loss, metabolic profile with regards to insulin sensitivity, glycemic control and serum lipid values [12,13,14,15,16] These effects appear potentially very attractive for athletes needing to lose fat mass quickly but, curiously, despite the huge amount of scientific literature about ketogenic diets, their influence on sport performance remains poorly investigated. Kreider and colleagues studied the effect of a specific exercise program in overweight woman with a VLCKD or normal carbohydrate content diet [17], but only few papers that focus on the influence of VLCKD on sports performance have been published, and with conflicting results: showing benefits [18,19], no effect [20,21] or impairment [22,23]
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