VBLOC Therapy by EnteroMedics

ASMBS Issues Position Statement on VBLOC for Obesity

VBLOC Therapy by EnteroMedics The American Society For Metabolic And Bariatric Surgery (ASMBS) recently issued a Position Statement on Vagal Blocking Therapy for Obesity.

VBLOC, or Vagal Blocking Therapy, is a new therapy for weight loss that uses an implantable, pacemaker-like device to intermittently disrupt the vagus nerve signaling between the brain and the stomach, affecting perceptions of hunger and fullness.

The VBLOC device, the Maestro Rechargeable System, was developed by EnteroMedics of St. Paul, Minnesota. It was approved by the U.S. Food and Drug Administration (FDA) in January 2015.

Position Statement

The position statement recommends the new therapy, saying “the ASMBS currently supports VBLOC for the treatment of obesity… based on current clinical knowledge and published peer-reviewed scientific evidence available at this time.”

The ASMBS states:

  • The quantity of data available at this time (six published studies and approximately 600 implanted devices) and the length of follow-up (12 to 18 months) indicate adequate safety and efficacy in the short term
  • More prospective studies with longer follow-up are required to establish the clinically significant efficacy and patient tolerance of this device

The six published studies listed in the position statement include three open label and two randomized double-blind sham-controlled clinical trials (EMPOWER trial and ReCharge trial) with up to 18-months follow-up, and a small prospective study with 12-month follow-up.

What is the Vagus Nerve?

The vagus nerve is one of 12 cranial nerves. Cranial nerves emerge from the brainstem and relay information between the brain and parts of the body. The vagus nerve is the longest of the cranial nerves, extending from the brainstem to the abdomen by way of multiple organs including the heart, lungs, upper digestive tract, and other organs of the chest and abdomen.

The vagus nerve regulates many activities in the body, from keeping the heart rate constant to controlling food digestion, as well as providing two-way communication between the brain and body.

  • 20% of vagus nerve fibers send instructions from the brain to the stomach; these signals control gastric acid secretion, digestive enzyme secretion, gastric capacity, and blood glucose.
  • 80% of vagus nerve fibers send instructions from the stomach to the brain; these signals control satiety (hunger), satiation (fullness), and energy metabolism.

The gastrointestinal and metabolic mechanisms regulated by the vagus nerve includes: the expansion of the stomach as food enters, stomach contractions that break down food into smaller pieces, the release of gastric acid to process food, emptying of the stomach contents into the small intestine, secretion of digestive pancreatic enzymes that enable calorie absorption, and sensations of hunger, satisfaction, and fullness.

About VBLOC Therapy

VBLOC Therapy affects perceptions of hunger and fullness. It works by intermittently blocking vagal nerve signals (messages involving food intake and digestion that travel back and forth between the brain and stomach) using high-frequency, low-energy, electrical impulses.

The device, called the Maestro System, is a pacemaker-like device that consists of a rechargeable electrical pulse generator, wire leads and electrodes that get surgically placed into the abdomen.

The implantation procedure is performed laparoscopically and takes about 60 to 90 minutes. It is usually done on an outpatient basis. The normal digestive system anatomy is not altered and the therapy allows for a normal diet and lifestyle.

Once implanted, the device is non-invasively programmed by the doctor to meet the personal needs of the patient. The therapy programming information is delivered across the skin into the device using radiofrequency technology and a transmit coil. The transmit coil is also used to recharge the device with an external mobile charger.

The device can be adjusted, deactivated, reactivated, or completely removed if desired.

The Maestro System is FDA-approved to treat patients aged 18 and older who have not been able to lose weight with a weight loss program, and who have a body mass index of 40 to 45, or 35 to 39.9 with at least one other obesity-related condition, such as type 2 diabetes, high blood pressure, or high cholesterol levels.

In the clinical study for FDA approval:

  • Serious adverse events included nausea, pain at the neuroregulator site, vomiting, and surgical complications. Other adverse events included pain, heartburn, problems swallowing, belching, mild nausea and chest pain.
  • After 12 months, the treatment group lost 8.5% more of its excess weight than the sham group; about half (52.5%) of the patients in the treatment group lost at least 20% of their excess weight; and 38.3% of patients in the treatment group lost at least 25% of their excess weight.

The FDA approval found that while the clinical study did not meet its original endpoint of at least 10% greater weight loss in the treatment group than the sham group at 12-months, the 18-month data was supportive of sustained weight loss and that the benefits of the device outweighed the risk for use in patients who met the criteria for use.

About the ASMBS

The American Society for Metabolic & Bariatric Surgery (ASMBS) is the largest non-profit medical organization in the world dedicated to metabolic and bariatric surgery, and obesity-related diseases and conditions. It was established in 1983, with the vision “to improve the public health and well being of society by lessening the burden of obesity and obesity-related diseases throughout the world.” Members include surgeons, nurses, bariatricians, psychologists, dieticians and other medical specialists focused on the disease of obesity. The ASMBS is also an advocate for healthcare policy to promote patient access to high quality prevention and treatment of obesity.


  • “American Society for Metabolic and Bariatric Surgery Position Statement on Vagal Blocking Therapy for Obesity,” published online December 7, 2015
  • FDA News Release, “FDA approves first-of-kind device to treat obesity” January 14, 2015
  • EnterMedics Website (enteromedics.com)

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