If you are eating high fat meals, it could be caused by your gallbladder..I was just reading about how when people follow a high carb/ low fat diet their gallbladder stops working then when the switch is made to high fat/low carb it shocks it into working again and it can cause pains in the upper right quadrant,colic,etc etc....rapid weight loss can cause gallstones too..you might want to search some threads here that mention gallbladder....