Effect of Endurance Exercise on Hepatic Lipid Content, Enzymes, and Adiposity in Men and Women

Obesity and physical inactivity are independent risk factors for the development of nonalcoholic fatty liver disease (NAFLD). We determined the effect of endurance exercise training on hepatic lipid content and hepatic enzyme concentration in men and women. Waist circumference (WC), percent body fat (BF), computed tomography (CT) scans for liver attenuation (inverse relationship with hepatic lipid), bilirubin, alanine aminotransferase (ALT), and gamma-glutamyltransferase (GGT) plasma concentrations were measured before and after 12 weeks of endurance training in 41 lean and obese men and women. Exercise training did not change liver attenuation, body weight, percent BF, bilirubin, or ALT concentration, but did lower WC (P < 0.0001), and decreased GGT in men only (P = 0.01). Obese subjects had a lower liver attenuation than lean subjects (P = 0.04). Obese women had lower ALT than obese men (P = 0.03). GGT was lower in women before and after training. WC was positively correlated with GGT (r = 0.32, P = 0.003) and ALT (r = 0.320, P = 0.004) and negatively correlated with liver attenuation (r = -0.340, P = 0.03). Percent BF was negatively correlated with bilirubin (r = -0.374, P = 0.005). Liver attenuation was negatively correlated with ALT (r = -0.405, P = 0.003). Short-term endurance training without weight loss does not alter hepatic lipid content. There was a strong relationship between GGT/ALT and body composition (percent BF) as well as between ALT and hepatic lipid content.