Changes in Insulin Sensitivity After Weight Loss
Condition: Obesity; Type 2 Diabetes Mellitus; Insulin Resistance
MeSH terms: Diabetes Mellitus, Type 2; Insulin Resistance; Hypersensitivity; Weight Loss
Study type: Observational

Summary: 
      This study is designed to compare the changes in insulin sensitivity as well as
      gastrointestinal hormone levels in diabetic and non-diabetic obese individuals who are
      undergoing weight loss procedures. The main hypothesis of this study is that weight loss
      induced by gastric bypass will induce a greater improvement in insulin sensitivity compared
      with gastric banding or low calorie diet. Subjects will be studied before and after weight
      loss. Studies consist of intravenous glucose tolerance test, body composition analysis, meal
      test, and energy expenditure.
    

Detailed description: 
      Patients who are scheduled for gastric bypass (GBP), sleeve gastrectomy (SG), or simple
      caloric restriction with gastric banding (BND) or a very low calorie diet (VLCD) will be
      examined at baseline weight, and when 6-10% total body weight has been lost. We will measure
      insulin sensitivity with an intravenous glucose tolerance test, and fasting levels of
      hormones that regulate food intake and insulin sensitivity, such as ghrelin, peptide YY
      (PYY), glucagon-like peptide 1 (GLP1) and leptin. Fat mass and skeletal muscle mass will be
      measured by dual photon absorptiometry (DXA). We will also measure the hormonal and thermic
      response to food with a liquid test meal and energy expenditure by indirect calorimetry. This
      measures how many calories are burned at rest and the in response to food. Subjects with
      diabetes will continue to be studied with the same protocol on an annual basis out to 5 years
      in order to determine the rate of remission of diabetes and the durability of this effect as
      subjects tend to regain some body weight over time.

      Subjects with diabetes will also be followed every three months for the first year after the
      initial weight loss for HbA1c and fasting glucose levels. The results of this study may lead
      to new understanding about changes in insulin sensitivity, body composition and hormonal
      profile, as well as changes in energy expenditure with weight loss after bariatric surgery or
      with simple caloric restriction. With this greater understanding, new treatments for obesity
      and diabetes, that do not require surgery, may be developed.
    

Intervention name(s): Gastric bypass; Gastric banding; Sleeve gastrectomy; Very low calorie diet
Intervention type(s): Procedure; Procedure; Procedure; Behavioral
Intervention description(s): NOTE: the surgery is not paid for by the study; NOTE: the surgery is not paid for by the study; NOTE: the surgery is not paid for by the study; Weight loss with calorie restricted liquid diet. Subject will be asked to stay in our in-patient research unit for 2-3 weeks and consume only those foods supplied by our bionutrition unit. Expected weight loss should be between 7-10% of body weight. Subjects will receive the diet at no cost and will be compensated for their time.
Other intervention name(s): GBP; BND; SG; VLCD
Observational model: Case-Control
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Subjects will be recruited by physician referral and from outpatient obesity, bariatric
        surgical clinics and endocrinology clinics at Columbia University Medical Center as well as
        from the Medical Center Community and metropolitan area via IRB-approved flyers and
        internet postings. Subjects will also be recruited from the following website:
        www.craigslist.com using the same posting format of the IRB-approved flyers.
      
Biospecimen description: 
      The researchers may want to retain your blood and/or tissue sample(s) so that additional
      research studies can be done now or in the future.
    
Keywords: Insulin resistance; Insulin sensitivity; bariatric surgery; diabetes; calorie restriction; body composition