Nutrition and Medicine 2013, 1(1): 10 Page 1 of 27 Page 1 of 27 RESEARCH ARTICLE A pilot case study on the impact of a self-prescribed ketogenic diet on biochemical parameters and running performance in healthy and physically active individuals Rainer J Klement 1,2* , Thomas Frobel 3 , Torsten Albers 4 , Sven Fikenzer 5 , Jan Prinzhausen 5 and Ulrike Kämmerer 6 1 Department of Radiation Oncology, University Hospital of Würzburg, 97080 Würzburg, Germany 2 Department of Radiotherapy and Radiation Oncology, Leopoldina Hospital, 97421 Schweinfurt, Germany 3 PREDIA GmbH, Virchowstr. 22, 97072 Würzburg, Germany 4 albers-concepts, Zuercher Str. 113, 8952 ZH-Schlieren, Switzerland 5 Department of Fitness and Individual Training, German University of Applied Sciences for Prevention and Health Management, 66125 Saarbrücken, Germany 6 Department of Obstetrics and Gynaecology, University Hospital of Würzburg, 97080 Würzburg, Germany * Correspondence: rainer_klement@gmx.de Abstract Background: Ketogenic diets (KDs) have gained some popularity not only as effective weight-loss diets and treatment options for several diseases, but also among healthy and physically active individuals for various reasons. However, data on the effects of ketosis in the latter group of individuals are scarce. We therefore collected pilot data on the physiological response to a self-prescribed ketogenic diet lasting 5-7 weeks in a small cohort of healthy and physically active individuals. Methods: Twelve subjects (7 males, 5 females, age 24-60 years) who followed moderate to intensive exercise routines underwent blood testing, bioelectrical impedance analysis (BIA) and spiroergometry during an incremental treadmill test. On the next day, they went on a self-prescribed KD for a median of 38 days (range 35-50 days), after which the same tests were performed again. Ketosis was self-monitored by urinary ketone strips. Subjective feeling during the diet was assessed by a questionnaire after the intervention. Due to the small and heterogenous sample, the results are interpreted in the context of the already existing literature. Results: The KDs were tolerated well by the majority of individuals. Impaired recovery from exercise remained the most frequently reported side effect until the end of the study. Most blood parameters remained stable during the intervention. However, there were significant elevations of total and LDL cholesterol concentrations (p<0.01) and a trend towards increased HDL- cholesterol (p=0.05). The drastic reduction of carbohydrates had no statistically significant influence on running performance judged by the time to exhaustion, VO2max and respiratory compensation points. BIA measurements showed significant increases in phase angle (p=0.01) indicating improvements of body composition with an estimated decrease of 3.4 kg of fat mass (p=0.002) and gain of 1.3 kg of fat free mass. We discuss the validity of these estimates taking into account a possibly altered hydration status due to the KD. Conclusions: Active healthy individuals will probably experience no major problems during a short term KD lasting several weeks. The drastically reduced carbohydrate content of the diet seems to be no limiting factor for running Received: 26.04.2013 Accepted: 28.06.2013 Published: 11.07.2013