Glycemic Index/Saturated Fatty Acid Diet and Hepatic Fat
Condition: Fatty Liver, Nonalcoholic; Diet, Healthy; Obesity
MeSH terms: Fatty Liver; Non-alcoholic Fatty Liver Disease
Study type: Interventional

Summary: 
      Excessive fat in the liver is associated with impairments in metabolic health. Reducing the
      amount of carbohydrates and fat both have been shown to reduce liver fat. However, not only
      the amount fats and carbohydrates, but also their quality have been shown to influence liver
      fat. Diets high in saturated fatty acids (SFA) and diets with a high glycemic index (GI) have
      been shown to increase liver fat content. However, available data from human dietary
      intervention studies is limited and these studies did not reflect a realistic diet. In the
      present study a combination of low GI/SFA on the one hand and high GI/SFA on the other hand
      is used to reflect realistically a healthy and an unhealthy diet as they are actually
      consumed by the Dutch population.

      The primary objective of this study is to investigate whether a two-week low compared to high
      GI/SFA diet reduces liver fat content. In addition, it will be investigated whether a two-
      week low compared to high GI/SFA diet reduces DNL, lowers the 24-hour glycemic response,
      lowers hepatic glycogen content, increases hepatic fat oxidation and changes hepatic lipid
      composition. Furthermore, the metabolic response to a meal (metabolites related to energy
      metabolism and substrate oxidation) will be studied upon the low and high GI/SFA diets.
    

Detailed description: 
      Rationale:

      Excessive fat in the liver is associated with impairments in metabolic health. Reducing the
      amount of carbohydrates and fat both have been shown to reduce liver fat. However, not only
      the amount fats and carbohydrates, but also their quality have been shown to influence liver
      fat. Diets high in saturated fatty acids (SFA) and diets with a high glycemic index (GI) have
      been shown to increase liver fat content. However, available data from human dietary
      intervention studies is limited and these studies did not reflect a realistic diet. Here the
      investigators want to combine low GI/SFA on the one hand and high GI/SFA on the other hand to
      reflect realistically a healthy and an unhealthy diet as they are actually consumed by the
      Dutch population. It is hypothesized that such a low compared to a high GI/SFA diet reduces
      liver fat content and possibly liver fat composition. Furthermore, underlying pathways
      involved in mediating those changes in liver fat are largely unknown. Hepatic lipid storage
      can originate from several metabolic pathways, including de novo lipogenesis (DNL) or
      decreased hepatic fat oxidation. Based on current literature the investigators hypothesize
      that with the diets chosen here, both DNL (by differences in GI) and fat oxidation (by
      differences in fat composition) will be involved in causing changes in liver fat.

      Objective:

      The primary objective of this study is to investigate whether a two-week low compared to high
      GI/SFA diet reduces liver fat content. In addition, it will be investigated whether a two-
      week low compared to high GI/SFA diet reduces DNL, lowers the 24-hour glycemic response,
      lowers hepatic glycogen content, increases hepatic fat oxidation and changes hepatic lipid
      composition. Furthermore, the metabolic response to a meal (metabolites related to energy
      metabolism and substrate oxidation) will be studied upon the low and high GI/SFA diets.

      Study design:

      This is a randomized cross-over study comparing the effects of a high GI/SFA compared to a
      low GI/SFA diet.

      Study population:

      Up to seventeen healthy overweight/obese males and postmenopausal females, aged between 45-75
      years and BMI between 27-38 kg/m2 will participate in the study (minimally 13 volunteers need
      to finish the study).
    

Intervention name(s): High GI/SFA diet; Low GI/SFA diet
Intervention type(s): Behavioral; Behavioral
Intervention description(s): Subject will adhere to a 2 week high GI/SFA diet.; Subject will adhere to a 2 week low GI/SFA diet.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: NAFLD; Diet; Glycemic index