The Impact of Low-fat and Full-fat Dairy Consumption on Glucose Homeostasis (DAIRY Study)
Condition: Insulin Resistance; Metabolic Syndrome; Obesity; Diabetes; NAFLD; Inflammation
MeSH terms: Metabolic Syndrome; Insulin Resistance; Inflammation
Study type: Interventional

Summary: 
      This randomized controlled feeding trial aims to determine whether the consumption of
      different amounts and types of dairy products affects blood sugar regulation and
      cardiometabolic health in men and women with the metabolic syndrome.
    

Detailed description: 
      This is a randomized controlled feeding trial designed to investigate whether the consumption
      of a diet rich in low-fat dairy vs. full-fat dairy vs. a limited dairy diet differentially
      affects glucose homeostasis. The researchers will also begin an investigation into the
      mechanisms by which dairy may affect glucose tolerance and its determinants. The
      investigators will study 60 men and women with the metabolic syndrome who will consume diets
      differing in their type and content of dairy foods, in a parallel-design randomized
      controlled trial consisting of a 4-week wash-in diet period and a 12-week dietary
      intervention period.

      Subjects will be randomized using block randomization stratified by gender and insulin
      resistance (low insulin resistance vs. high insulin resistance or manifest diabetes) to one
      of three diet groups, which they will follow for 12 weeks: the limited dairy diet, the
      low-fat dairy diet, or the full-fat dairy diet. During the dietary intervention, participants
      will be provided with specific amounts and types of dairy products by the Human Nutrition Lab
      (HNL) at Fred Hutchinson Cancer Research Center (FHCRC). In the limited dairy diet arm,
      participants will be asked not to consume any dairy, other than three servings of nonfat milk
      per week, which will be provided. In the two dairy diet arms, participants will be asked to
      consume 3.3 servings per day of either nonfat/low-fat or full-fat milk, yogurt, and cheese.
      Participants will be asked to consume all of the dairy products they receive, not to consume
      any other dairy products for 12 weeks, and to continue consuming their habitual diet ad
      libitum (i.e., to eat only when hungry, and to stop eating when comfortably satiated).

      Prior to randomization, subjects will complete a wash-in diet period of 4 weeks during which
      they will be asked to consume the limited dairy diet (i.e., consume 3 servings of nonfat milk
      per week, and not consume any other dairy products). In the third week of the wash-in diet
      period, subjects will also complete their first of two 5-day controlled feeding periods
      (i.e., consume study dairy products alongside a provided standard American diet) to measure
      ad libitum energy intake. During the last week of the wash-in diet period, participants will
      be admitted to clinic for a baseline visit (clinic visit #1). After clinic visit #1, subjects
      will be randomized to one of the three study arms, as outlined above. They will follow their
      randomly assigned study diet for the next 12 weeks. In the second week of the main
      intervention period, subjects will complete their second 5-day controlled feeding period to
      again measure ad libitum energy intake, this time on the specific intervention diet they had
      been randomized to. In the last week of the 12-week diet phase, subjects will be admitted for
      the follow-up clinic visit (clinic visit #2). At both clinic visits, the researchers will
      collect fasting blood; measure body weight and height, waist and hip circumference, and blood
      pressure; conduct a 3-hour FS-OGTT to assess glucose tolerance, insulin sensitivity, and
      pancreatic beta-cell function; conduct a whole-body DEXA scan to assess body fat mass, lean
      mass, and body fat distribution; and an abdominal MRI scan to assess liver triglyceride
      content and the ratio of intra-abdominal to subcutaneous adipose tissue. Subjects will also
      complete five Food Frequency Questionnaires (FFQ's) and five unannounced 24-hour dietary
      recalls during the study to assess dietary intakes.

      The primary analysis will be a per protocol analysis that will include at least 60
      participants (at least 20 in each intervention arm) who comply with all study procedures per
      protocol. The investigators anticipate enrolling up to 72 participants to achieve this goal.
      In a secondary analysis, the researchers will analyze the impact of the dietary intervention
      on all enrolled participants, including those who dropped out, were excluded, or
      non-compliant with the study protocol, in an intent-to-treat (ITT) analysis that will be
      reported and interpreted together with the per protocol analysis.
    

Intervention name(s): Limited dairy diet; Low-fat dairy diet; Full-fat dairy diet
Intervention type(s): Other; Other; Other
Intervention description(s): Consumption of no dairy foods other than 3 servings per week of nonfat milk for 12 weeks; Consumption of 3.3 servings per day of low-fat milk, yogurt, and cheese for 12 weeks; Consumption of 3.3 servings per day of full-fat milk, yogurt, and cheese for 12 weeks
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Diabetes; Metabolic syndrome; Obesity; NAFLD