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.
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.
Study Type
OBSERVATIONAL
Enrollment
119
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
Columbia University Medical Center
New York, New York, United States
Change in Insulin Sensitivity
Measured by frequently sampled intravenous glucose tolerance test (FSIVGTT)
Time frame: 2-8 weeks
Change in Body Composition
Measured by dual energy x-ray absorptiometry (DXA)
Time frame: 2-8 weeks
Change in Resting Energy Expenditure
Measured by indirect calorimetry using a Hood Calorimeter
Time frame: Up to 4 hrs post-meal
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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.