It is a prospective randomized trial on 218 subjects, 109 for each arms. The purpose of this trial is to compare very low calorie diet and metabolic surgery induced weight loss and its maintenance.

Obesity is a leading public health issued associated with poor quality of life, morbidity and an increased mortality rate. Although metabolic surgery results in a greater weight loss when compared to non-surgical approaches, a low calorie diet associated with intensive maintenance session may be a valid alternative for weight loss. Since lifestyle interventions are safer and potentially more cost effective than metabolic surgery, this trial will test whether an intensive lifestyle intervention is as effective as metabolic surgery to induce weight loss and its maintenance.

A total of 218 participants will be randomly assigned to metabolic surgery (109) or intensive lifestyle intervention (109).

Clinical outcomes will be assessed at 25% reduction in Body Mass Index (BMI), at 12 months and 24 months.

Inclusion Criteria:

• Aged between 19 and 69 years
• Body Mass Index ≥35 kg/m2 and at least one or more obesity-related co-morbidities such as type II diabetes (T2DM), hypertension, sleep apnea and other respiratory disorders, non-alcoholic fatty liver disease, osteoarthritis, lipid abnormalities, gastrointestinal disorders, or heart disease
• Body Mass Index ≥40 kg/m2

Exclusion Criteria:

• Pregnancy
• Active cancer
• End stage renal failure
• End stage liver failure
• Being unable to understand and sign informed consent