Background: Although the prevalence of nonalcoholic fatty liver disease (NAFLD) has been increasing, there have been few studies of long-term changes in NAFLD in large numbers of subjects. This study was performed to assess the long-term changes in severity of fatty liver and to analyze the association with changes in body weight and lifestyle factors.
Methods: We analyzed lifestyle factors, biochemical data, and abdominal ultrasonography in subjects who underwent voluntary medical checkups at a 5-year interval. Fatty liver on ultrasonography was graded as normal, mild, moderate, or severe by the degree of echogenicity.
Results: The analyzed population consisted of 2895 subjects of age 47+/-8.7 years (range, 20-79 years). Among the 1938 subjects who had normal livers at baseline, 374 subjects (19%) developed fatty liver 5 years later. Those who developed fatty liver showed more weight gain, increase of aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transferase (gamma-GT), and glucose levels during the 5-year period. Among the 930 subjects who had fatty liver at baseline, 263 (28%) subjects showed a decrease in grade and 209 (22%) progressed to a higher grade of fatty liver after 5 years. The group with a lower grade lost -2.2+/-4.3 kg of body weight from baseline, and reduction in hepatic steatosis grade was associated with decreased serum AST, ALT, triglycerides, gamma-GT, and fasting glucose levels.
Conclusions: Even a small weight reduction was associated with improvements in NAFLD and related metabolic abnormalities such as dyslipidemia and hyperglycemia. Subjects with fatty liver should be advised to lose weight through lifestyle modifications.