The effects of dietary weight loss with or without exercise training on liver enzymes in obese metabolic syndrome subjects

Aim: Insulin resistance and visceral adiposity are predisposing factors for fatty liver disease. The main objectives of this study were (i) to compare the effects of caloric restriction (CR) alone or together with moderate-intensity aerobic exercise training (CR+EX) on liver enzymes, a surrogate marker of liver injury, in obese metabolic syndrome (MetS) subjects and (ii) to identify anthropometric, metabolic, cardiovascular and dietary predictors of changes in liver enzymes. Methods: Sedentary men and women (n = 63), aged 55 ± 6 (s.d.) years with body mass index 32.7 ± 4.1 kg/m² and confirmed MetS, were randomized to 12-week CR, CR+EX or no treatment (Control). Results: Weight loss averaged 7.6% in the CR and 9.1% in the CR+EX group (time effect, p < 0.001; group effect, p = 0.11); insulin sensitivity improved by 49 and 45%, respectively (both p < 0.001). Fitness (maximal oxygen consumption) increased by 19% in the CR+EX group only (p < 0.001). Alanine aminotransferase (ALT) levels decreased by 20% in the CR and 24% in the CR+EX group (time effect, both p < 0.001; group effect, p = 0.68); corresponding values for γ-glutamyltransferase (GGT) were -28 and -33%, respectively (time effect, both p < 0.001; group effect, p = 0.28). Reduction in abdominal fat mass (measured by DXA from L1 to L4) independently predicted ΔALT (r = 0.42, p = 0.005) and ΔGGT (r = 0.55, p < 0.001), whereas change in dietary saturated fat intake was independently associated with ΔALT (r = 0.35, p = 0.03). Conclusions: Reductions in central adiposity and saturated fat intake are key drivers of improvement in liver enzymes during lifestyle interventions. Exercise training did not confer significant incremental benefits in this study.