The purpose of the study is to determine the effect of three weight loss surgeries compared to a low calorie diet with regard to energy expenditure, body composition, insulin sensitivity, and the response of gastrointestinal peptides to a standard meal. Baseline assessments will be conducted in all four groups and changes will be compared six and fifty-two weeks post-operatively.

The purpose of the study is to determine the effect of three weight loss procedures compared to a low calorie diet. Three different obesity surgery methods; Roux-en-Y gastric bypass (RYGB), gastric banding (GBa), sleeve gastrectomy (SGx), and one low calorie diet program on metabolism, with regard to body fat, physical activity levels, hormone changes after eating a meal, and changes in taste preferences.

Participants having obesity surgery will receive laparoscopic (minimally invasive surgery performed by making several small incisions in the abdomen and inserting a camera called a laparoscope) an adjustable gastric band, a sleeve gastrectomy or roux en Y gastric bypass. In addition to the regular surgical procedures, the surgeons will remove laparoscopically about 10g (1 tablespoon) of fat from within the abdomen. This fat tissue will be processed and stored for future study (at completion of the study) of your metabolism pre-treatment. Participants will complete post-operative follow-up appointments with their surgeon as required.

Participants on the LCD program will experience weight loss by following a low calorie diet program (LCD). For this diet you will select all your own food choices and our dietitians will assist you to reach your daily calorie target. You will be asked to follow this balanced food diet for the remainder of the 12 month study.

Inclusion Criteria:

• Men and women between ages of 18-65 years
• Body mass index >40 kg/m2 (BMI is calculated from your height and weight)
• BMI >35 kg/m2 with obesity associated diseases that should improve with weight loss (diabetes, hypertension, and sleep apnea)
• Medically qualified for obesity surgery by Drs LeBlanc or Hausmann

Exclusion Criteria:

• Women who are pregnant or unwilling to avoid pregnancy for 2 years post-operatively.
• Diabetes diagnosed more than 5 years ago
• Have had diabetes for more than 5 years
• Have had surgery on your stomach or intestinal tract except to remove your appendix or gall bladder.
• Have an active disease in your stomach or intestinal tract including inflammatory bowel disease.
• Have thyroid disease that is not treated
• Have any of the following psychiatric conditions that have not been treated to the point of complete remission: binge eating disorder, bulimia, current physical abuse, current sexual abuse, current substance abuse or dependence, mania or psychosis.
• Have any of the following psychiatric conditions that have not been treated to the point of partial remission prior to your enrollment in this study: anxiety, depression, dysfunctional marriage/family, personality disorder or post-traumatic stress disorder.
• Have a failure of one of your major organ systems. For example, liver failure, kidney failure, severe blood vessel blockage, or are not mentally able to understand the study and give your consent.
• Have a heart pacemaker or defibrillator, or any type of non-removable, metal containing objects in your body, as well as those with tattoos containing metallic dyes.
• Can not drink milk or products containing milk.
• Taking medications that alter your weight or metabolic rate. For example, antipsychotic drugs, beta adrenergic drugs (beta blockers), as well as anorectic drugs.

Medically qualified for obesity surgery by Drs LeBlanc or Hausmann