Effect of Macrocomposition on Nonalcoholic Fatty Liver Disease (NAFLD) in Bariatric Surgery Candidates
Condition: Morbid Obesity; Non-alcoholic Fatty Liver Disease
MeSH terms: Liver Diseases; Fatty Liver; Non-alcoholic Fatty Liver Disease; Obesity, Morbid
Study type: Interventional

Summary: 
      Nonalcoholic Liver disease (NAFLD) is known to be caused by deposition of fat in the liver.
      The impact of NAFLD on bariatric surgery is of great concern. Enlarged fatty livers increase
      the operative complications of bariatric surgery and weight loss prior to bariatric surgery
      has been shown to reduce complications of surgery. Most bariatric surgery programs use a
      conventional low fat, calorie restricted diet during the preparation phase for surgery. The
      investigators will compare the effects of the low carbohydrate versus the low fat diets on
      weight loss, reduction in liver fat content, and liver size. These results will provide new
      clinical insights into the optimal dietary intervention to make bariatric surgery safe and
      effective for the increasing numbers of patients opting for this aggressive therapy for
      morbid obesity. Patients approved for bariatric surgery by the University of Michigan
      Bariatric Surgery multidisciplinary committee will be randomly assigned to either a 1000 to
      1200 calorie low fat or low carbohydrate, 8-week study diet. All the food for this study will
      be provided for free by the study team. Participants will be required to meet with the study
      team weekly to pick up study food and for a nutritional consult. These visits will occur in
      the eight weeks preceding the patient's bariatric surgery procedure. During the bariatric
      surgery, a liver biopsy will be performed to assess the impact of the study diet on liver fat
      content.
    

Detailed description: 
      The obesity epidemic has lead to increased morbidity and morality from cardiovascular disease
      and Type 2 diabetes. One co-morbidity of obesity is nonalcoholic fatty liver disease (NAFLD),
      which is characterized by excess fat deposition in the liver. About a third of the overweight
      and obese population has NAFLD and this rises to 80 to 90% of morbidity in obese patients.
      Short-term weight loss and caloric restriction leads to a reduction in hepatic fat content,
      suggesting an ability of the liver to quickly respond to dietary interventions. Manipulation
      of the diet macronutrient composition in order to achieve quicker weight loss as well as
      improve adverse metabolic consequences attributable to excess weight has attracted much
      attention and controversy. Multiple clinical studies have shown that low carbohydrate diets
      can provide more rapid weight loss in individuals in the short-term and that most have no
      trouble adhering to the diet for up to 6 months. Most bariatric surgery programs use a
      conventional low fat, calorie restricted diet during the preparation phase for surgery.
      However, no systematic comparison of diets with different macronutrient compositions have
      been performed. In this study we propose to compare the clinical effects of a low
      carbohydrate versus a low fat diet in individuals which can derive an immediate benefit from
      interventions that have the potential to reduce hepatic fat content: individuals that are
      preparing for bariatric surgery (laparoscopic Roux-en-Y gastric bypass surgery or adjustable
      laparoscopic gastric banding). Enlarged steatotic livers increase the operative risk of
      bariatric surgery and weight loss prior to bariatric surgery has been shown to reduce
      operative risk. We hypothesize that the use of a 1000 to 1200 kcalorie low carbohydrate diet
      (< 15% of total kcaloric intake) during the preparation phase for bariatric surgery will
      cause a greater reduction in weight, hepatic fat content and hepatic volume compared to a
      "conventional" 1000 to 1200 kcalorie low-fat diet (30% fat, 60% carbohydrates of total
      kcaloric intake) and offer clinical advantages by making the technical aspects of surgery
      easier. Thus, the data collected will provide significant new clinical insights into the
      effect of diets with different macronutrient composition. These results will provide a basis
      for larger clinical trials to identify the optimal dietary intervention to make bariatric
      surgery safe and effective for the increasing numbers of patients opting for this aggressive
      therapy for morbid obesity.
    

Intervention name(s): low carbohydrate diet; low-fat diet
Intervention type(s): Other; Other
Intervention description(s): 1000 to 1200 kcalorie low carbohydrate diet (< 15% of total kcaloric intake); 1000 to 1200 kcalorie low-fat diet (30% fat, 60% carbohydrates of total kcaloric intake)
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Investigator)
Primary purpose: Treatment
Keywords: morbid obesity; non-alcoholic fatty liver disease; bariatric surgery; low fat diet; low carbohydrate diet