A composition capable of elevating blood adiponectin level and enlarging LDL particle size and thus lowering the concentration of small dense LDL in blood to thereby prevent diabetes and a heart disease such as a coronary artery disease or ameliorate the symptoms of these diseases, which originates in a natural material, shows a high safety without any side effect even in continuous intake over a long period of time, and is usable as a health food or drink. A composition comprising as the active ingredient a fermented tea extract which has an effect of elevating adiponectin level and an effect of enlarging LDL particle size.