Surgical management of Morbid Obesity is increasingly frequent. A low-calorie diet is recommended with the main goal of reducing intrahepatic fat infiltration, fat tissue and making easier the surgery. Information the use pharmacological interventions during the preoperative period in this population are rare.

This is a randomized, control trial to investigate the effect and safety of Phentermine in patients with obesity who need a bariatric surgery (BMI >35 kg/m2 with comorbidities or BMI > 40 kg/m2).

Screening will be made to select eligible participants before intervention. Participants were randomly assigned to one of two groups (low-calorie diet + phentermine 15 mg or low-calorie diet + placebo) for therapies during 6 weeks. Anthropometric measurements (weight, body composition, body mass index and waist-hip index), serum metabolic profile (glucose, total cholesterol, HDL-c, LDL-c, triglycerides, and HOMA-IR) markers of inflammation (IL-1, IL-6 and PCR) and hepatic ultrasound will be measured 2 times for each participant. Surgical complications (anastomosis filtration, intestinal obstruction or stenosis, need to perform open surgery and mortality) will be evaluated. Adverse events associated with phentermine (blood pressure, cardiac frequency, headache, gastrointestinal symptoms, euphoria, anxiety and insomnia) will be collected.

Inclusion Criteria:

• Women and men
• >18 years and <55 years old.
• Diagnosis of obesity grade II with comorbidities
• Diagnosis of obesity grade III with or without comorbidities
• Approved to bariatric surgery by an interdisciplinary committee
• Having signed the Informed consent form

Exclusion Criteria:

• Use of addictive substances

  • Inability or lack of understanding to achieve lifestyle and behaviour changes
  • Mental disease
  • Severe Pulmonary disease
  • Giant Hiatal hernia, gastric or duodenal ulcer
  • Unstable coronary artery disease
  • Portal hypertension or esophageal varices
  • Surgical or anesthetic high risk

double-blinded