Short-term weight loss and hepatic triglyceride reduction: evidence of a metabolic advantage with dietary carbohydrate restriction.
Study Goal
The researchers aimed to determine the effectiveness of dietary carbohydrate and calorie restriction on reducing hepatic triglycerides in subjects with NAFLD, with a secondary focus on changes in plasma alanine aminotransferase levels.
Results Summary
The study found that plasma alanine aminotransferase levels did not decrease significantly with weight loss, unlike aspartate aminotransferase. Reductions in hepatic triglycerides were greater with carbohydrate restriction than calorie restriction, potentially due to enhanced oxidation.
Population
18 subjects (5 men, 13 women) with NAFLD, mean age 45 ± 12 y, BMI 35 ± 7 kg/m².
Effective Dosage
Not specified for alanine (study focused on dietary carbohydrate restriction <20 g/d or calorie restriction 1200-1500 kcal/d).
Duration
2 weeks.
Interactions
None mentioned.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
carbohydrate-restricted diet (<20 g/d) | decrease | liver triglycerides | NAFLD subjects | -55 ± 14% | decreased | #1 |
calorie-restricted diet (1200-1500 kcal/d) | decrease | liver triglycerides | NAFLD subjects | -28 ± 23% | decreased | #2 |
carbohydrate-restricted diet (<20 g/d) | decrease | weight | NAFLD subjects | -4.6 ± 1.5 kg | reduced | #3 |
calorie-restricted diet (1200-1500 kcal/d) | decrease | weight | NAFLD subjects | -4.0 ± 1.5 kg | reduced | #4 |
dietary intervention (≈4.3% weight loss) | decrease | hepatic triglycerides | subjects with NAFLD | ≈42% | reduced | #5 |
weight loss | decrease | plasma aspartate aminotransferase | - | - | decreased | #6 |
weight loss | no change | plasma alanine aminotransferase | - | - | showed no effect | #7 |
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 lipogenesis. 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/m(2)) 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 = -0.797, 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. This trial was registered at clinicaltrials.gov as NCT01262326.