The roles of different chain length ω-hydroxylated fatty acids in lipid metabolism are indicated by increased ω-hydroxylation of MCFAs by CYP4A P450s in rodents during fasting, by peroxisome proliferators, and in hepatic steatosis while decreased CYP4F genes expression by peroxisome proliferators and during starvation results in reduced ω-hydroxylation of LCFAs and VLCFAs. This evidence concerns the gene CYP4F3 and fatty liver disease.