The Effects of Cocoa Flavanols on Insulin Resistance in an 'At-risk' Population
Condition: Insulin Resistance
MeSH terms: Insulin Resistance
Study type: Interventional

Summary: 
      The aim of the current study is to investigate the ability of antioxidants found in cocoa
      ('flavanols') to increase the body's sensitivity to the hormone insulin. 32 overweight or
      mildly obese women, who are otherwise healthy, will be recruited. Subjects will attend the
      laboratory on 3 occasions after fasting from midnight. The 1st visit is a medical screening,
      with laboratory visits 2 and 3 separated by 4 weeks, during which time subjects will consume
      a cocoa drink (containing either high or low amounts of flavanols) twice a day. Subjects will
      record their food intake for 3-days before visit 2 and in week 3 of consuming the cocoa. They
      will also eat a diet of standard macronutrient composition for 3 days before visits 2 and 3.
      During the 5 hour laboratory visits, subjects will have a scan to assess their body
      composition using a low-dose x-ray machine (Dual Energy X-ray Absorptiometry; DEXA), and have
      their insulin sensitivity measured using a 3 hour hyperinsulinemic, euglycaemic Clamp.
    

Detailed description: 
      Background; Overweight and mild obesity are associated with insulin resistance and mild
      elevations in lipid risk factors which are not usually sufficiently abnormal to merit
      treatment. Such people are encouraged to lose weight to reduce their risk of progressing to
      type 2 diabetes and coronary heart disease, but there is clearly a potential role for dietary
      modifications to maximize any potential benefit of this weight loss. Cocoa flavanols (CF) are
      known to have vascular effects which might enhance substrate delivery to metabolically active
      tissues, and thus improve insulin sensitivity.

      Aims; This randomized, double blind, placebo controlled, parallel design study aims to
      investigate the longer term effects of CF intake on insulin sensitivity. It is hypothesized
      that studying otherwise healthy overweight and mildly obese subjects, with evidence of
      fasting insulin resistance, would show whether there was potential benefit of CF in an 'at
      risk' population.

      Experimental protocol and methods; 32 overweight or obese women (Body Mass Index 27-35), who
      are otherwise healthy, will be recruited onto the study. They will attend the 'David
      Greenfield Human Physiology' laboratories on 3 convenient mornings, following an overnight
      fast. The 1st visit is a medical screening and will involve signing a consent form,
      completing a medical screening and food frequency questionnaire, having height, weight,
      hip/waist circumference measurements taken and a 10ml sample of blood taken for routine
      analysis. Subjects will then be asked to complete a 3-day diet diary for macronutrient
      assessment and to consume a diet providing 50% of energy as carbohydrate for 3 days prior to
      the 2nd laboratory visit. This 2nd visit will involve having a DEXA body composition scan and
      a 3-hour hyperinsulinaemic, euglycaemic glucose clamp. Starting on the following morning,
      subjects will then consume a cocoa drink (containing either 450mg or 25mg of CF) twice a day
      for 28 days. A 3-day diet diary for macronutrient assessment will be recorded during week 3
      of taking the cocoa and a standardized diet will be consumed for 3 days prior to the final
      laboratory visit, as before. This 3rd visit will be identical to visit 2 and occur
      immediately after 28days of taking the cocoa.

      Measurable end points Insulin sensitivity 'M' value (mg glucose disposal from the blood/kg
      body weight.min), Respiratory exchange ratio, Resting metabolic rate, Homeostatic model
      assessment for insulin resistance (HOMA-IR) Body composition (DEXA) Macronutrient composition
      of the diet before and during the intervention period
    

Intervention name(s): High Flavanol Cocoa; Low Flavanol Cocoa
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): cocoa consumed as a 24g dairy based cocoa drink mix, twice a day (mid-morning & early evening on an empty stomach), for 4 weeks.; cocoa consumed as a 24g dairy based cocoa drink mix, twice a day (mid-morning & early evening on an empty stomach), for 4 weeks.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: Insulin resistance; obesity; cocoa; women