Short-term weight loss and hepatic triglyceride reduction: Evidence of a metabolic advantage with dietary carbohydrate restriction

Background: Individuals with nonalcoholic fatty liver disease (NAFLD) have excess intrahepatic triglycerides. This is due, in part, to increased hepatic synthesis of fat from carbohydrates via lipo-genesis. Although weight loss is currently recommended to treat NAFLD, little attention has been given to dietary carbohydrate restriction. Objective: The aim of this study was to determine the effectiveness of 2 wk of dietary carbohydrate and calorie restriction at reducing hepatic triglycerides in subjects with NAFLD. Design: Eighteen NAFLD subjects (n = 5 men and 13 women) with a mean (±SD) age of 45 ± 12 y and a body mass index (in kg/m¹) of 35 ± 7 consumed a carbohydrate-restricted (<20 g/d) or calorie-restricted (1200-1500 kcal/d) diet for 2 wk. Hepatic triglycerides were measured before and after intervention by magnetic resonance spectroscopy. Results: Mean (±SD) weight loss was similar between the groups (-4.0 ± 1.5 kg in the calorie-restricted group and -4.6 ± 1.5 kg in the carbohydrate-restricted group; P = 0.363). Liver triglycerides decreased significantly with weight loss (P < 0.001) but decreased significantly more (P = 0.008) in carbohydrate-restricted subjects (-55 ± 14%) than in calorie-restricted subjects (-28 ± 23%). Dietary fat (r = 0.643, P = 0.004), carbohydrate (r = -0.606, P = 0.008), posttreatment plasma ketones (r = 0.755, P = 0.006), and respiratory quotient (r = -0.191, P < 0.001) were related to a reduction in liver triglycerides. Plasma aspartate, but not alanine, aminotransferase decreased significantly with weight loss (P < 0.001). Conclusions: Two weeks of dietary intervention (=4.3% weight loss) reduced hepatic triglycerides by =42% in subjects with NAFLD; however, reductions were significantly greater with dietary carbohydrate restriction than with calorie restriction. This may have been due, in part, to enhanced hepatic and whole-body oxidation.