Provided is a composition for the prevention or treatment of obesity, dyslipidaemia, fatty liver or insulin resistance syndrome, comprising piperonal as an active ingredient. The composition of the present invention can be used to advantage as a drug or functional food composition which not only exhibits activity in the prevention or treatment of obesity, hyperlipidaemia or fatty liver but which also causes a significant reduction in fasted blood sugar and blood insulin concentration and hence has an effect in improving Type-2 diabetes or insulin resistance and also improves metabolic disorder which is closely associated therewith.