The present invention is concerned with a system and method for preventing or substantially reducing the occurrence of gastroesophageal reflux in a human or animal, in particular by the fixation of a valve based device (10) within the stomach of such a human or animal, about the lower oesophageal sphincter muscle, which device supersedes the operation of said lower oesophageal sphincter muscle, in particular in situations when the lower oesophageal sphincter muscle is damaged.
