Popular Diets Study
Condition: Obesity; Insulin Resistance
MeSH terms: Insulin Resistance
Study type: Interventional

Summary: 
      The aim of this study is to evaluate the effects of three dominant dietary patterns -
      conventional low-fat, low-glycemic index (GI) and very-low-carbohydrate - on energy
      metabolism and heart disease risk factors following weight loss in obese young adults in a
      feeding study
    

Detailed description: 
      For most of the last half century, reduction in fat intake has been the primary nutritional
      approach for the prevention and treatment of obesity and cardiovascular disease (CVD). Over
      the last few years, very low carbohydrate (Atkins-type) diets have achieved great popularity,
      with publication of several studies suggesting greater weight loss and improvements in CVD
      risk factors over 3 to 6 months. Recently, a third dietary approach focused on glycemic index
      (GI) has generated interest. However, few studies have compared the effects of these diets on
      body weight regulation and risk for CVD. The primary hypotheses of this study are that any
      diet that lowers the postprandial rise in blood glucose (very-low-carbohydrate or low-GI)
      will have beneficial effects on the physiological adaptations to weight loss and on some CVD
      risk factors. However, other CVD risk factors will be adversely affected by a
      very-low-carbohydrate vs. a low-GI diet. Preliminary data provide strong support for these
      hypotheses, by showing that resting energy expenditure declines less and CVD risk factors
      improve more with weight loss on a low-glycemic load diet compared to a conventional low-fat
      diet. This application proposes a cross-over feeding design to study the effects of three
      diets following 12.5% weight loss in obese young adult subjects (n = 24, age 18 to 40 years).
      The diets are: 1) conventional low-fat, with 60% carb, 20% fat, 20% protein; 2) low-GI with
      40% carb, 40% fat, 20% protein; and 3) very-low-carbohydrate with 10% carb, 60% fat, 30%
      protein. The primary outcome is resting energy expenditure (indirect calorimetry). Secondary
      outcomes include total energy expenditure (doubly labeled water), thermic effect of food
      (indirect calorimetry), physical activity (accelerometry), insulin resistance and B-cell
      function (frequently-sampled OGTT), blood lipids, blood pressure and measures of systemic
      inflammation and coagulopathy. This study should have major public health implications to the
      millions of Americans currently following diets to decrease body weight and risk for heart
      disease.
    

Intervention name(s): Low glycemic index diet; Low fat diet; Very low carbohydrate diet
Intervention type(s): Other; Other; Other
Intervention description(s): Feeding protocol, all foods prepared in a metabolic kitchen; Feeding protocol, all foods prepared in a metabolic kitchen; Feeding protocol, all foods prepared in a metabolic kitchen
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: obesity; nutrition