Thank you for the query.
Fatty liver can be caused by alcohol abuse
) or the cause can be nonalcoholic (nonalcoholic steatohepatitis). Nonalcoholic is mostly caused by obesity, fatty foods intake, diabetes.
Such condition can lead to liver cirrhosis and liver failure
, and it is the risk factor of liver cancer. Your brother has also impaired fasting glucose
what is prediabetes state.
As your brother is very young he should do something with it, otherwise it can lead to serious complications.
Physical activity and low fat diet is strongly advisable.
Hope this will help.