Non-randomized open label study to investigate factors mediating changes in insulin sensitivity, glucose tolerance and other metabolic outcomes after bariatric surgery.

Bariatric and weight loss surgery is an effective treatment for severe obesity. Bariatric surgery also decreases insulin resistance and improves diabetes. Our study enrolled individuals approved for bariatric surgery to collect data on modifiable predictors and laboratory outcomes. These data would allow us to systematically assess clinical outcomes over one year post bariatric surgery and elucidate how insulin resistance is decreased and diabetes is improved.

The type of surgery was selected by the subjects between Roux-en-Y gastric bypass or a laparoscopic adjustable gastric banding. Participation in the study involved having a small sample of tissue obtained from the abdomen and subjects were also given the option to have a biopsy performed in the thigh area during their elective surgical procedure (optional adipose and muscle tissue biopsies).

Subjects were examined prior to surgery and at 2, 3, 6 months after intervention. Anthropometric and body composition measurements were performed using the Bioelectrical Impendence Analysis (BIA) before surgery and 6 months post operatively. Morning blood was collected after overnight fasting during each visit. Some of the non-diabetic subjects completed a mixed nutrient stimulation study during the baseline and 6-month visit. Blood samples were collected immediately prior to drinking the liquid drink, and every 30 minutes after the meal ingestion for 2 hours.

Inclusion Criteria:

1. males and females
2. 18-65 years old
3. approved for bariatric surgery as per BIDMC Bariatric Clinic guidelines
4. English-speaking
5. willing and able to take part in a multi year study involving telephone interviews and enrolled prior to bariatric surgery

Exclusion Criteria:

1. Any condition that would exclude a patient from bariatric surgery as listed below:

   1. patients with untreated major depression or psychosis
   2. binge eating disorders
   3. current drug and alcohol abuse
   4. severe cardiac disease with prohibitive anesthetic risks
   5. severe coagulopathy
   6. inability to comply with nutritional requirements including life-long vitamin replacement.
   7. pregnancy

2. Any additional condition not in accordance with standard of care as per Bariatric Clinic at BIDMC.

3. Any condition which in the opinion of the investigators rendered the candidate unsuitable for participation in this study.

Exclusion Criteria for Optional Biopsy:

1. history of any illness, other than obesity, that may affect insulin sensitivity (diabetes anemia, infectious diseases, renal or hepatic failure, uncontrolled hypertension, cancer or lymphoma)
2. subjects who required special diet prior to surgery
3. chronic inflammatory conditions such as inflammatory bowel disease and rheumatoid arthritis
4. states of cortisol or growth hormone excess
5. any medications that are known to influence glucose metabolism such as glucocorticoids
6. a known history of anaphylaxis or anaphylactoid-like reactions or who have a known hypersensitivity to anesthetic agents such as Lidocaine or Novocaine
7. a known history of bleeding dyscrasia or poor wound healing
8. any medical condition precluding supine position