I recommend you to refer the following article .

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4093690/

any diet contains high levels of cholesterol or carbohydrates can do the job 

only FRUCTOSE overdose 

https://www.researchgate.net/publication/224825141_Metformin_protects_against_the_development_of_fructose-induced_steatosis_in_mice_Role_of_the_intestinal_barrier_function

Article Metformin protects against the development of fructose-induc...

There is several Models exists for NASH in rodent , simply use pubmed or google scholar for this .

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3353364/

Dear Alex Thomas,

There are many animals models you can find for NASH. For one of our study we have developed the NASH model in SD rats using high fat diet. Also, you can check fructose diet-induced NASH model in rodents.

Regards

Vishwanatha GL