Amsterdam, The Netherlands, September 15, 2015 -- Prolonged sitting time as well as reduced physical activity contribute to the prevalence of non-alcoholic fatty liver disease (NAFLD) in a study of middle-aged Koreans. These findings support the importance of both reducing time spent sitting and increasing physical activity, say researchers. Their results are published in the Journal of Hepatology. 
 
 Physical activity is known to reduce the incidence and mortality of various chronic diseases. However, more than one half of the average person's waking day involves sedentary activities associated with prolonged sitting such as watching TV and using the computer and other devices. 
 
 Recently, attention has focused on the damaging effects of sedentary behavior regardless of additional physical activity. A growing number of epidemiologic studies have suggested an association between sedentary behavior and chronic diseases including obesity, diabetes, insulin resistance, metabolic syndrome, cardiovascular disease, cancer, and even death that is distinct from those related to a lack of physical activity. This association was still observed among patients participating in high levels of moderate to vigorous physical activity, indicating that regular high levels of physical activity do not fully protect against the risks associated with prolonged periods of sedentary behaviors. However, the association between physical activity and NAFLD has been largely unexplored. 
 
 In the current study researchers examined the association of sitting time and physical activity level with NAFLD in Korean men and women to explore whether any observed associations were related to the amount of body fat. They studied records of nearly 140,000 Koreans who underwent a health examination between March 2011 and December 2013. Physical activity level and sitting time were assessed using the Korean version of the international Physical Activity Questionnaire Short Form. The presence of fatty liver was determined using ultrasonography. 
 
 Of the people studied, nearly 40,000 had NAFLD. Importantly, the researchers found that both prolonged sitting time and decreased physical activity level were independently associated with increasing prevalence of NAFLD. Remarkably, these associations were also observed in patients with a body mass index (BMI) of less than 23. 
 
 Lead investigator Seungho Ryu, PhD, MD, of the Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, South Korea, explained, "We found that prolonged sitting time and decreased physical activity level were positively associated with the prevalence of NAFLD in a large sample of middle-aged Koreans." Co-author Yoosoo Chang, MD, PhD, added: "Our findings suggest that both increasing participation in physical activity and reducing sitting time may be independently important in reducing the risk of NAFLD, and underlines the importance of reducing time spent sitting in addition to promoting physical activity." 
 
 "The data from Ryu and colleagues add to the strong and alarming evidence that sitting too much and moving too little has significant negative consequences for cardio-metabolic health," commented Michael I. Trenell, PhD, Professor of Metabolism & Lifestyle Medicine at Newcastle University, UK, and an expert on how lifestyle influences lifelong health and wellbeing and chronic disease. 
 
 "The message is clear, our chairs are slowly but surely killing us. Our body is designed to move and it is not surprising that sedentary behavior, characterized by low muscle activity, has a direct impact on physiology. With a dearth of approved drug therapies for NAFLD, lifestyle changes remain the cornerstone of clinical care. The challenge for us now is to 'stand up' and move for NAFLD, both physically and metaphorically," Professor Trenell added. 
 
 ### ||||| Sitting for long periods has been linked to obesity, diabetes and heart disease — and now there's new evidence that it may also increase the risk of liver disease, according to a new study from South Korea. 
 
 In the study, researchers found that people who sat for 10 or more hours daily had a 9 percent greater risk of developing a condition called nonalcoholic fatty liver disease (NAFLD) than those who spent less than five hours a day sitting. 
 
 Physical activity also played a role in people's risk of NAFLD: Those who were physically active were 20 percent less likely to develop the disease compared with those who were inactive, according to the study published today (Sept. 15) in the Journal of Hepatology. [How Many Calories Am I Burning? (Infographic)] 
 
 "The amount of time spent doing sedentary activity such as sitting at a computer or watching TV has increased dramatically in recent years," Dr. Seungho Ryu, professor of occupational and environmental medicine at Kangbuk Samsung Hospital in South Korea and lead author of the study, told Live Science. Now, "more than half of the average person's waking day involves sedentary activities," he said. 
 
 In the study, the researchers looked at more than 139,000 Korean men and women who reported their levels of physical activity and sitting time. NAFLD was confirmed using ultrasounds. 
 
 The average age of the participants was 39.9 years, according to the study. Because the people in the study were generally healthy -- young and middle-age men and women -- it's unlikely that other health problems can explain the link between sitting time and physical activity with NALFD, Ryu said. 
 
 The study suggests that regular physical activity, even at a high intensity, does not fully protect against the risks associated with prolonged sitting, he said. If the results of the study are confirmed, it will be important to encourage people to both increase their physical activity and reduce their sitting time to reduce the risk of developing NAFLD, he said. 
 
 Even doing light activity instead of sitting may help reduce the risk of NAFLD, Ryu added. 
 
 "Our body is designed to move, and it is not surprising that sedentary behavior, characterized by low muscle activity, has a direct impact on physiology," Michael Trenell, a professor of metabolism and lifestyle medicine at Newcastle University in England, wrote in an editorial that accompanied the study in the journal. 
 
 Sedentary behavior can increase the risk of insulin resistance and can lower cardiovascular function, he wrote. In people with insulin resistance, body cells lose their ability to respond to insulin by taking in sugar from the blood, leading to high blood sugar levels, and, sometimes, Type 2 diabetes. 
 
 "What remains less certain is the effect of sedentary behavior on the liver," he said. 
 
 Currently, there is a lack of drugs approved for treating people with NALFD, so lifestyle changes are the primary means of treating the disease, Trenell wrote. In general, 150 minutes of moderate exercise per week or 10,000 steps per day are considered good rules of thumb for physical activity, he wrote. 
 
 "However, the current literature cannot inform us how much sitting is too much," Trenell wrote. "We just know that it is better to sit less than to sit more." 
 
 About 19 percent of Americans have NALFD, according to a 2013 study in the American Journal of Epidemiology. The condition can lead to swelling and scarring of the liver, according to the American Liver Foundation. 
 
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– Too much sitting is already linked to a higher risk of anxiety disorder and certain types of cancer. Now you can throw liver disease into the mix, too. A new study out of South Korea finds those who spend at least 10 hours a day on their behinds have a 9% higher risk of developing nonalcoholic fatty liver disease, or NAFLD, than those who sit for less than five hours a day. The finding remained true even for those with a BMI of less than 23, which is considered normal. The study also found a link between NAFLD and exercise, as physically active participants were 20% less likely to develop the disease, author Seungho Ryu tells Live Science. But physical activity should replace sitting time, rather than attempt to make up for it. "Our findings suggest that both increasing participation in physical activity and reducing sitting time may be independently important in reducing the risk of NAFLD," a co-author says in a release. It isn't clear how sitting affects the liver, but researchers say other health problems are unlikely to explain the link to NAFLD because the study was based on 139,000 generally healthy Koreans with an average age of 40. The findings are important because "the amount of time spent doing sedentary activity such as sitting at a computer or watching TV has increased dramatically in recent years," Ryu says. An expert suggests getting 150 minutes of moderate exercise per week or taking 10,000 steps per day. "The message is clear, our chairs are slowly but surely killing us," he says. "Our body is designed to move." About 19% of Americans suffer from NAFLD, which can cause the swelling and scarring of the liver, and most are forced to change their lifestyle. (Standing might not be so great, either.)