Obesity and insulin resistance are central part of metabolic syndrome . However some people with normal weight also exist glucose and lipid metabolism disorder including hypertension hyperlipidemia hyperglycemia subclinical inflammation etc. These people are called metabolically unhealthy normal weight. As the current diagnostic criteria for metabolic syndrome and obesity are inconsistent the definition of metabolically unhealthy normal weight is also inconsistent in different studies. Health hazards of metabolically normal weight including increased risk of cardiovascular disease tumor kidney damage cholelithiasis and low testosterone were found in recent studies. Metabolic unhealthy normal weight may be related to body weight body composition intestinal flora dietary patterns and age but the specific mechanism remains unclear. Compared with obese patients the metabolically abnormalities in these people are easy to be ignored or missed. And intervention studies of large sample population in metabolic unhealthy normal weight are lacking. We reviewed the population distribution risks and possible influencing factors of metabolic unhealthy in patients with normal weight aiming to improve the attention to these patients.