The present invention relates to a method for preventing or treating dyslipidemia or fatty liver, comprising: administering to a mammalian subject in need thereof a therapeutically effective amount of a composition comprising nonenal. The present composition containing nonenal as an active ingredient is very effective in preventing or treating obesity, diabetes, dyslipidemia, fatty liver or insulin resistance syndrome (preferably, dyslipidemia or fatty liver, more preferably hyperlipidemia or fatty liver). The composition of the present invention useful as pharmaceuticals compositions or functional food compositions has therapeutic efficacies for obesity, diabetes, hyperlipidemia or fatty liver, and also induces significant decrease in fasting glucose level and blood insulin level to improve type 2 diabetes, insulin resistance and related metabolic disorders.
