I am a physician (but don't take this as medical advice, just some guidance.)
The most common risk factor associated for non-alcoholic
fatty liver disease (NAFLD) is insulin resistance seen in metabolic syndrome. In fact, NAFLD is now referred to as the liver manifestation of metabolic syndrome.
The fact that you have elevated glucose (and are not diabetic) is a risk factor. Genetics always play some role, but genetic factors are not well understood and certainly are not modifiable. There are other causes of fatty liver (viral hepatitis, high cholesterol, drugs, medications, perhaps excessive consumption of fructose, etc.), but I assume your GI doc has addressed these. If not, get another opinion and consider seeing an endocrinologist.
10-20% of Americans have fatty liver, another 2-6% have a much more severe progression of fatty infiltration called nonalcoholic steatohepatitis (NASH). Here is a link from the National Institutes of Health that is primarily about NASH but also has information on NAFLD that you might find interesting.
Please do not minimize the impact of your eating on your liver function. Some people can develop NAFLD with relatively little amount of excess weight. Dietary management seems to be key, assuming that other factors are not involved.
I agree with bargoo above about Googling "fatty liver" and "patient education"; make a list of questions for your doctor before the next visit; and set the agenda yourself.