A trial of a very low calorie diet prior to cholecystectomy operation in obese patients

INTERVENTION: Intervention group: two week pre‐operative very low calorie diet Control group: continue normal diet CONDITION: Obese patients undergoing elective cholecystectomy surgery ; Nutritional, Metabolic, Endocrine ; Obesity PRIMARY OUTCOME: Duration of surgery SECONDARY OUTCOME: 1. Pre‐operative weight loss; 2. Post operative complication rate; 3. Post operative length of stay; 4. Post operative day case rate; 5. Perceived difficulty of the operation INCLUSION CRITERIA: 1. Adult patients with capacity to consent 2. Body mass index (BMI) over 30kg/m2 3. Symptomatic gallstone disease placed on a waiting list for elective laparoscopic cholecystectomy operation