Good to see your concerns about health. As far as , gamma glutamyl tranferase is concerned you might be knowing that it is an enzyme secreted whenever bile ducts/liver are under some of stress. If you are getting some fat that might accomulate in the form of bile stones that may obstruct the bile passages and causing the release of GGT. On the other hand alcohol consumption is a major cause of disease related to biliary tract/liver but its not the only one cause thats why primary physicians might ask about drinking patterns of patients. In your case most probable cause seems to be damage of liver and biliary ducts due to excess fat. Consult your primary surgeon , if he/she advises removal of gall bladder then you should consider it. Wishing you a healthy life. Regards