1. Introduction
Obesity, overweight, NAFL
OBESITY
These authors contributed equally to this work.Background: Current guidelines aim to limit the dietary glycemic index (GI) and intake of saturated fatty acids (SFA). Several studies have shown favorable effects of low-GI or low-SFA diets on intrahepatic lipid content (IHL), but these studies were performed under overfeeding conditions or extreme differences in GI or SFA to maximize the contrast between diets. By combining changes in GI and SFA, we can mimic how people can improve their diet in a realistic setting. Objectives: We investigated the effect on liver fat content and substrate metabolism of both reducing GI and replacing SFA with polyunsaturated fat in practically realistic amounts under isocaloric conditions. Design and Methods: In a randomized crossover study, thirteen overweight participants consumed two diets, one high in GI and SFA (high GI/SFA) and one low in GI and SFA (low GI/SFA) with identical macronutrient composition, for two weeks each. Diets were equal in caloric content, consisted of habitual food items, and had a macronutrient composition that can be easily achieved in daily life. At the end of each intervention, IHL content/composition and liver glycogen were measured by magnetic resonance spectroscopy. Additionally, fasted and postprandial hepatic de novo lipogenesis and glycemic and metabolic responses were investigated. Results: IHL was significantly lower (−28%) after the two-week low-GI/SFA diet (2.4 ± 0.5% 95% CI [1.4, 3.4]) than after the two-week high-GI/SFA diet (3.3 ± 0.6% 95% CI [1.9, 4.7], Obesity is a major health problem worldwide and its prevalence continues to rise [Importantly, not only does the percentage of energy (En%) from dietary fat and carbohydrates seem to be of significant importance but also their quality [In addition, the underlying pathways involved in the modulation of liver fat content by such diets are of interest. Unraveling these pathways could help identify targets that can be used to treat NAFL. For example, it has been suggested that the type of fatty acid may affect whole-body fat oxidation. Stable isotope studies show that exogenous SFA is oxidized to a lesser extent than unsaturated fatty acids [Here, we investigated whether consumption of a low-GI/SFA diet for two weeks, compared with an isocaloric high-GI/SFA diet, reduces liver fat content in overweight individuals. In addition, we studied whether decreases in liver fat content were parallel to an increase in whole-body fat oxidation, a decreased glycemic response, reduced hepatic glycogen levels, reduced hepatic de novo lipogenesis, and a decreased saturated hepatic fat fraction.