Effect of Gastric Bypass Surgery on Energy Metabolism

Study Overview
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Brief Summary
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The purpose of this study is to investigate the short term and long term effects of Roux-en-Y gastric bypass (RYGB) surgery on energy expenditure, gastrointestinal and appetite regulating hormone levels, and appetite sensation. We hypothesize that following RYGB surgery, metabolism will be elevated in comparison to patients who have not yet had RYGB but who are losing weight simultaneously using a low calorie diet. We further hypothesize that this higher metabolism will be associated with alterations in fasting and postmeal levels of gastrointestinal and appetite regulating hormones. Long term (1.5 years after RYGB), we hypothesize that differences in metabolism, body composition, and hormone levels will distinguish between patients who have maintained their weight loss after RYGB vs those who have regained weight.

Official Title
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ERGEM: Effect of Roux-en-Y Gastric Bypass Surgery on Energy Metabolism.

Conditions
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Obesity

Intervention / Treatment
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* Procedure: Roux-en-Y gastric bypass surgery
* Dietary Supplement: low calorie diet (1,000 kcal/day)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 18-65 BMI ≥40, or ≥35 with concomitant obstructive sleep apnea, or hypertension scheduled for RYGB surgery at Hvidovre Hospital, Copenhagen, Denmark Must have lost between 1-4% body weight after 3 months of dietary counselling Exclusion Criteria: Deemed ineligible for RYGB surgery by patient's own physician(s) Diabetes Mellitus Non Caucasian Weight >160kg (due to DEXA scanner limitations), or morphologically unable to accommodate in DEXA scanner (>40cm in maximum supine anterior-posterior dimension, or >60cm in maximum supine body width) Hemoglobin <7.0 mmol/L Psychiatric illness under the care of a psychiatrist Eating disorder such as bulimia Patients on special diets (eg vegetarian, Atkins) Any history of thyroid dysfunction, or use of thyroid medication (with the exception of transient thyroiditis) Hypothalamic or genetic etiology of obesity A current diagnosis of cancer Any surgery other than RYGB planned in the ensuing 3 months Substance abuse or smoking Use of prescription medications or over-the-counter drugs affecting metabolism Excessive intake of alcohol (>7 drinks/week) Excessive intake of caffeine (>300 mg/day) Presence of any contraindication to use of a low calorie powder diet, including: Past history of ventricular arrhythmias (even if treated) Renal dysfunction (creatinine clearance <60 mL/min) Liver enzymes (ALT or AST) >3x upper limit of normal Milk protein allergy, or lactose intolerance Porphyria or phenylketonuria History of gout Breastfeeding Concomitant use of monoamine oxidase inhibitors or non potassium sparing diuretics Inability or unwillingness to comply with a low calorie diet protocol Patients who find the powder diet products to be unpalatable Do not enjoy yogurt, carrots, or milk (as these are essential elements of the low calorie diet)

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Earlier gastric bypass surgery (7 weeks)<br>These patients will undergo gastric bypass surgery 7 weeks after starting a low calorie diet, and will continue the low calorie diet for 3 weeks following surgery. | Procedure: Roux-en-Y gastric bypass surgery<br>* Briefly, RYGB is characterized first by creation of a small stomach pouch. The small intestine is then divided approximately 75 cm distal to the ligament of Treitz, creating a proximal intestinal limb that transports the secretions from the stomach remnant, liver, and pancreas, and a 'Roux' limb, that is attached to the new stomach pouch to drain consumed food. The distal end of the proximal limb is then reattached approximately 100 cm distal to the new stomach drainage site, creating a common channel where digestive enzymes mix with ingested food.<br>Dietary Supplement: low calorie diet (1,000 kcal/day)<br>* Patients will consume a daily diet composed of: 4 powder diet portions (Cambridge Diets, UK) plain yogurt (100-125g) skim milk (1L) a limited variety of vegetables The diet will be consumed by both groups for a 10 week period.<br>* Other names: Cambridge Weight Plan, Northants, UK.;|
| Active Comparator: Later gastric bypass surgery (10 weeks)<br>These patients will undergo gastric bypass surgery 10 weeks after starting a low calorie diet. | Procedure: Roux-en-Y gastric bypass surgery<br>* Briefly, RYGB is characterized first by creation of a small stomach pouch. The small intestine is then divided approximately 75 cm distal to the ligament of Treitz, creating a proximal intestinal limb that transports the secretions from the stomach remnant, liver, and pancreas, and a 'Roux' limb, that is attached to the new stomach pouch to drain consumed food. The distal end of the proximal limb is then reattached approximately 100 cm distal to the new stomach drainage site, creating a common channel where digestive enzymes mix with ingested food.<br>Dietary Supplement: low calorie diet (1,000 kcal/day)<br>* Patients will consume a daily diet composed of: 4 powder diet portions (Cambridge Diets, UK) plain yogurt (100-125g) skim milk (1L) a limited variety of vegetables The diet will be consumed by both groups for a 10 week period.<br>* Other names: Cambridge Weight Plan, Northants, UK.;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in 24 hour energy expenditure |  | 7 weeks, 10 weeks (short term); 1.5 years (long term) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| change in fasting bile acids and lipid profile |  | 7 weeks, 10 weeks (short term); 1.5 years (long term) | 
| changes in fasting levels of leptin, adiponectin, and visfatin |  | 7 weeks, 10 weeks (short term); 1.5 years (long term) | 
| change in body composition |  | 7 weeks, 10 weeks (short term); 1.5 years (long term) | 
| Change in appetite sensation |  | 7 weeks, 10 weeks (short term); 1.5 years (long term) | 
| change in fasting and postprandial levels of GLP-1, PYY, oxyntomodulin, glucose, insulin, C peptide, GIP, ghrelin, cholecystokinin |  | 7 weeks, 10 weeks (short term); 1.5 years (long term) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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obesity, bariatric surgery, energy expenditure, incretins, appetite regulation, body composition, GLP-1