Institute for Evidence in Medicine, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany. Department of Sports and Health, Paderborn University, Paderborn, Germany. Division of Metabolic and Nutritional Medicine, Department Paediatrics, Dr. von Hauner Children's Hospital, University of Munich Medical Center, LMU - Ludwig-Maximilians-Universität Munich, Munich, Germany. Cochrane Germany, Cochrane Germany Foundation, Freiburg, Germany.