Dietary Carbohydrate and Internal Body Fat
Condition: Adiposity
MeSH terms: Obesity
Study type: Interventional

Summary: 
      This is a 2-year randomized controlled trial to test the effect of dietary carbohydrates,
      both quality and quantity, on changes in internal body fat mass. Up to 250 women and men with
      obesity are recruited in Bergen, Norway, and randomized to one of the following normo- and
      isocaloric dietary patterns (same amount of protein, polyunsaturated fatty acids and moderate
      energy, 2,000 - 2,500 kcal per day): 1) a low-fat high-carbohydrate diet primarily with
      refined (e.g., flour-based) carbohydrate sources, 2) a low-fat high-carbohydrate diet based
      on minimally refined (e.g., cellular) carbohydrate sources, and 3) a very-high-fat
      low-carbohydrate diet.
    

Detailed description: 
      Obesity, and high internal fat storage in particular, represents a tremendous and increasing
      health challenge across the world, and is linked to the recent introduction and globalization
      of an ultra-processed food supply largely based on refined carbohydrates. However, more
      high-quality studies are needed to directly assess the role of carbohydrate quality in
      abdominal adiposity. We also need studies with greater long-term adherence to prescribed food
      profiles, which may be achievied with the help of new electronic tools such as meal planning
      applications.

      The participants select and plan all meals among a list of carefully designed options, using
      an application/recipe booklet developed for the study. Each recipe/meal/snack is designed to
      fully comply with the overall macronutrient- and dietary profile for the respective groups.
      We will further instruct the participants to record their meal choices during three days
      every 14 days, and to record all deviations throughout the intervention.

      Enrolled participants are invited to study visits at baseline and after 3, 6, 9, 12 and 24
      months. At all or some of these time points, the participants provide biological samples
      (blood, urine and feces, and for some, adipose and/or muscle tissue) and undergo phenotyping,
      e.g., measurement of body weight and fat mass by bioelectrical impedance analysis and
      low-radiation CT imaging, and a standardized meal test with blood sample collection up to 4
      hours postprandially. In addition, participants will be asked to fill out a collection of
      questionnaires that assess quality of life, motivation, fatigue, gastrointestinal health,
      appetite and physical activity. We ask the participants to maintain the same level of
      physical activity throughout the study.

      The primary outcome measure is change in internal body fat mass (visceral adipose tissue)
      measured by CT imaging. Secondary outcome measures include change in 2-hour postprandial
      serum concentrations of insulin, change in 4-hour postprandial serum concentrations of
      triacylglycerols, and change in fecal microbiota composition measured by 16S sequencing.
    

Intervention name(s): Acellular carbohydrate diet; Cellular carbohydrate diet; Low-carbohydrate high-fat diet
Intervention type(s): Behavioral; Behavioral; Behavioral
Intervention description(s): Participants will be asked to consume 2,000 - 2,500 kcals, thereof 45 energy percent (E%) carbohydrate (up to 5 E% added sugar), 30 E% fat (10-12 E% saturated fatty acids and 7-10 E% polyunsaturated fatty acids) and 17 E% protein. They will use an original online/smartphone application that provides choices of meals/food combinations/recipes corresponding to their prescribed macronutrient profile and dietary pattern. Participants are asked to complete 3-day dietary records every 14 days throughout the study, and to report any deviations from the planned interventions.; Participants will be asked to consume 2,000 - 2,500 kcals, thereof 45 energy percent (E%) carbohydrate (up to 1 E% added sugar), 38 E% fat (10-12 E% saturated fatty acids and 7-10 E% polyunsaturated fatty acids) and 17 E% protein. They will use an original online/smartphone application that provides choices of meals/food combinations/recipes corresponding to their prescribed macronutrient profile and dietary pattern. Participants are asked to complete 3-day dietary records every 14 days throughout the study, and to report any deviations from the planned interventions.; Participants will be asked to consume 2,000 - 2,500 kcals, thereof 10 energy percent (E%) carbohydrate (up to 1 E% added sugar), 73 E% fat (30 E% saturated fatty acids and 7-10 E% polyunsaturated fatty acids) and 17 E% protein. They will use an original online/smartphone application that provides choices of meals/food combinations/recipes corresponding to their prescribed macronutrient profile and dietary pattern. Participants are asked to complete 3-day dietary records every 14 days throughout the study, and to report any deviations from the planned interventions.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Body composition; Internal body fat; Dietary pattern; Dietary carbohydrate