Effects of Dietary Fructose Restriction on Liver Fat, De Novo Lipogenesis and Insulin Kinetics in Children with Obesity

In this study, published in Gastroenterology in February 2017, Jean-Marc Schwarz, Robert Lustig, et al., further analyze the data from a trial exploring the effects of adolescent fructose restriction, previously discussed on 190507.

Prior to this trial, a body of evidence had suggested fructose was in some way linked to metabolic distress, particularly fatty liver disease. No study, however, had shown that fructose, specifically, drives metabolic disease progression and that calorie-for-calorie, fructose is worse than other nutrients or even other carbohydrates.

During the trial, 43 obese adolescent children were fed a diet similar to their habitual diets (51% carbohydrate, 16% protein, and 33% fat, at a level of calories anticipated to lead to weight maintenance) but with most of the dietary sugar replaced with starch (the share of calories from sugar dropped from a baseline of 27.7% to 10.2%). All food was provided for the duration of the study and purchased from local supermarkets to best mimic foods available to subjects in the real world.

Subjects followed this diet for nine days. By day 10, the following metabolic changes had occurred:

• Median liver fat content decreased from 7.1% to 3.8%, and 37 out of 38 tested subjects showed a decrease in liver fat.
• Visceral adipose tissue volume decreased from 123 cm³ to 110 cm³.
• De novo lipogenesis (DNL) decreased significantly overall and in 37 out of 40 subjects.
• Measures of insulin sensitivity significantly improved.

The improvements in liver fat content and DNL production were also significant in the nine subjects who did not lose weight, which suggests these improvements were independent of any overall weight loss. (Note: The study was designed so all subjects maintained their baseline weight, but in practice many subjects lost weight despite researchers’ efforts.)

The results of this trial demonstrated that a specific reduction in fructose consumption within the context of an otherwise normal diet leads to significant improvements in liver fat content and insulin sensitivity in only nine days, independent of any weight loss. This suggests, at the very least, that fructose reduction or restriction can result in substantial health benefits in obese children with fatty liver disease.