Low HDL is mainly due to the following factors:1. Irregular diet: often eat fatty things, resulting in low HDL.2. Liver diseases: such as hepatitis B or cirrhosis.3. Bad habits: a lot of smoking, drinking, lack of exercise.4. Disease factors: renal failure, diabetes mellitus, nephrotic syndrome.5. Picky eaters: eat a lot of fatty things, usually picky eaters. Eat a lot of fatty things, usually picky eaters. HDL is a protective factor, the higher the better, mainly reverse transporter lipoproteins, so that the coronary atherosclerosis risk factors to reduce, so usually from the etiology of the treatment, need to pay attention to diet plus exercise, so that the higher the HDL the better.