He throw up all the time?

My stepdad eats a large amount of food. Like an amount good for 6people. Then everybody in the house notice that he throw up everyday right after eating. He keeps on runnin back to the bathroom and when my mom asked him he said he doesnt he stays in the bathroom that long cuz of his teeth(well we dont believe that crap. Hes been to dentist lastmonth and we see puke n d toilet) when someones using the bathroom he rush to go downstairs and the next day we see puke on the gr. He always lie that its his teeth everytime we go to restaurant or have dinner over aunts house. Its been goin on for years. What could that be?