The results revealed that dietary DHA and EPA operate by different mechanisms to modulate hepatic steatosis and hyperinsulinemia in fa/fa Zucker rats, and that DHA was the most effective among the n3-PUFA for elevating hepatic DHA levels, preventing progression of hepatic steatosis via reduced FAS, and reversing a marker associated with fibrosis despite elevation of some indicators of inflammation. The gene discussed is FAS; the disease is hyperinsulinism.