South Korea has been one of the thinnest countries in the world. According to the World Factbook (CIA, 2014), the obesity rate of South Korea (7.7%) was ranked 139th out of 191 countries in 2008. Upon growing familiarity with westernized cultures, the obesity percentage for the overall South Korean population has increased since the 1980s. For example, there have been drastic changes in South Korea’s food consumption patterns within the last thirty years; rice consumption has diminished over 50%, while consumption of meats and ready-to-eat has more than doubled for those periods. It is easy to find these trends in the Middle East, Pacific Islands, and Eastern European countries, where they have adopted westernized food consumption patterns recently, resulting in rapidly increasing rate of obesity. Increasing numbers of obese people are causes of some individual or social problems in some developed countries, mainly the United States and United Kingdom, and diffusing to other countries that have adopted westernized food consumption recently (See Table 1).Obesity problems bring with them a significant burden of not only individual mortality but also social exclusion and discrimination. For this reason, obesity problems impose direct and indirect costs in two ways: health and employment. First, substantial health care costs are associated with treating obesity and related symptoms. Also, social health care costs are higher for obese people than normal people. Second, obesity problems can lead to costs in employment. A higher level of sickness and absence from work among the obese reduces productivity and imposes costs on industries. Many obese people are not working as a direct result of their obesity, either because of health problems or for other reasons including discrimination in the workforce. Obesity can therefore reduce national output, reduce tax revenues, and increase government expenditures on incapacity benefits and unemployment benefits.Obesity has been traditionally determined using an individual’s Body Mass Index (BMI), calculated using height and weight. Since the 1970’-s, it has been suggested that individuals exist who are of a normal weight and height, but are affected by problems typically associated with obesity including type 2 diabetes, heart disease, and hyperinsulinemia. This condition has been defined as Metabolically Obese, Normal Weight (MONW) and the share of the MONW population has been increasing steadily. Ruderman et al. (1998) summarize several characteristics of the MONW; for example, MONW adults have a higher probability of developing type 2 diabetes than obese adults. Members of younger generations are more likely to be MONW than those of older generations. The fact that younger people make fewer physician visits than the elderly combined with the need for a comprehensive medical examination to detect MONW makes the condition difficult to diagnose. In addition, Lee (2009) characterizes properties of the Korean MONW. The MONW phenotype is significantly higher for those of older age, those with lower education, those who indulged in moderate alcohol consumption, and those who spend less time participating in moderate-intensity exercise.MONW people have the same two problems as the conventionally obese: health care costs and low productivity. However, the MONW are different in that they do not recognize their health status without medical inspection and are therefore unaware of their increased risk for diseases such as diabetes. The MONW therefore spend more in health care costs and show lower productivity than those without the condition. Since MONW people cannot be easily identified by potential employers, employers are unknowingly subject to extra risks-increased health insurance costs, lower productivity-when they hire MONW employees. Therefore, identification of MONW is an important issue for companies’ applicant screening process. Even though much medical research has been published on the MONW, this will be the first paper to consider the effects of the condition on the labor market from an economics perspective.The rest of the paper is organized as follows: I first review existing research on MONW and asymmetrical information theories in the first chapter. In the second chapter, I derive a testable hypothesis from previous studies about obesity and test it by using an empirical model and the Korea National Health and Nutrition Examination Survey (KNHNES). Finally, I summarize empirical findings and interpret implications from those findings in the previous chapter