This study aimed to clarify the relationship between health behavior and health literacy. The results suggested that the subjects with IFG were less likely to practice health behaviors and had lower health literacy than those without IFG. These results are similar to those of a previous study involving American adults . A study using data from the 2016 Behavioral Risk Factor Surveillance System (BRFSS) reported that adults with prediabetes had lower health literacy and more unhealthy behaviors compared with adults without prediabetes . Previous studies of patients with diabetes mellitus showed that patients with low health literacy had poor diabetes knowledge  and a high risk of developing unhealthy consequences due to poor health behaviors . This phenomenon is not only seen in adults with prediabetes, but also in adults with chronic diseases such as hypertension and cancer [22, 23], which can be interpreted as the impact of health literacy. It is known that the role of health literacy is to acquire, process, and understand basic health information and the services required to make appropriate healthcare decisions .
The results of this study indicate that the proportion of individuals with IFG who were actually using food and nutrition information was lower than that of individuals with non-IFG. Individuals with IFG need health and food information they can understand and use in order to maintain target blood glucose levels and properly manage their health . Fasting blood glucose levels and obesity are affected by balanced caloric intake rather than daily caloric intake . In addition, the outcome of body mass index (BMI) control through dietary intake and physical activity affects IFG ; thus, it is important to choose a balanced diet. Western countries are using strategies to improve individuals’ health literacy for managing their blood glucose and utilizing nutritional information on various foods [27, 28]. However, in South Korea, there is still a lack of understanding of food information and systems that can be properly utilized in everyday life . In several countries where there is a high illiteracy rate, low health literacy can be understood as an inability to read or understand essential health-related data, and thus, to manage health . However, the illiteracy rate is low in South Korea because of the high level of education; more than 80% of the subjects in this study had an educational background of 10th grade or higher. The low level of health literacy compared to the high level of literacy can be interpreted as a lack of health education and public relations in terms of health. Low health literacy may be affected by a lack of personal competencies to use information as well as health literacy-related demands and complexity. Previous studies have highlighted the importance of developing educational programs or strategies to improve individuals' health literacy , and there is a need in South Korea for strategies to increase accessibility to health information through the development and provision of effective health information media for adults with IFG. In addition, interventions for improving health education in primary care and community settings can be effective in changing health behavior . Thus, health literacy can improve health status, health-related attitudes, and health behavior . To enhance health behavior, educational interventions for improving health education should be implemented simultaneously with health promotion efforts.
Individuals with IFG and low health literacy were remarkably more likely to engage in unhealthy behaviors. In this study, 76.1% of subjects with IFG were found to be obese (BMI > 23 kg/m2). Since there was a very high correlation between an increase in BMI and the prevalence of diabetes mellitus and IFG , exercise and healthy eating habits for BMI control are considered important. However, our study found that “walking for 150 minutes or more per week” did not have a significant effect on IFG prevalence. It was also found that about 50% of all subjects “walked for 150 minutes or more a week,” indicating that about half of Korean adults have a considerable lack of activity. Studies have reported that the prevalence of IFG increased with a lack of exercise [19, 33]. Therefore, further studies are needed to understand basic metabolism in individuals with IFG, and consider the intensity and degree of exercise that affects the consequences of obesity and BMI.
The results of this study indicate that IFG prevalence was high in male subjects who were employed. This result is similar to the general characteristics of individuals with IFG as found in a previous study , and is also similar to the results of a study that showed Korean office workers as having various health problems such as diabetes mellitus due to a lack of exercise, poor eating habits, and drinking and smoking . Although the legal working hours per week in South Korea were shortened with the introduction of the 5-day workweek system in 2004, South Korea continues to have the longest work hours in the world . A substantial number of Korean office workers experience a lack of exercise due to their overtime work , and they experience many drinking problems due to the get-together culture and public drinking [34, 36]. The latter is accepted as an extension of work and serves as a causal factor for excessive drinking, regardless of individuals’ health statuses. In South Korea, where a get-together and drinking culture is developed such that people are encouraged to drink and have difficulty refusing to drink , and long working hours are prevalent , male workers who lack adequate stress-relieving methods other than drinking and smoking  face significant threats to their health . This study demonstrated that health literacy was related to sex, age, educational level, and economic level. Baker et al.  reported that those with low health literacy had poor health status and health management. The results of our study are consistent with those of previous studies, suggesting that more attention should be paid to persons with IFG.
This study has several limitations. First, since the subjects were examined based on responses to a multidimensional questionnaire at a single time point, this study could not analyze in detail the causal relationship between health literacy and health behavior factors affecting IFG. Second, we evaluated health literacy using two items (i.e., “recognition of nutrition fact labels” and “utilization of the nutrition facts labels”). Since an exact measurement of health literacy levels was not used, the relationship between health literacy level and health behavior in those with IFG could not be closely evaluated. Further studies using more detailed surveys are suggested to verify the results of this study.
Despite these potential limitations, our study has several strengths. This study used national statistical data that covered three years, and the subjects represented the total adult population in South Korea. The survey design included multi-level sampling, stratification, and clustering. Therefore, the results of this study can be generalized to the adult population of South Korea. In addition, the results confirmed the differences in health behavior and health literacy between Korean individuals with IFG and those with non-IFG. Particularly, individual with IFG have a poor tendency to use of health literacy to ensure the practice of health behaviors, such as exercise, avoiding alcohol, obesity management, and food information utilization in this study. Because health literacy is related to health status , national policies and support should be focused on mitigating the impacts of low health literacy in individuals with IFG. Above all, it is important for those with IFG to be aware of the importance of health literacy, so that they can practice effective health behavior.