The Smart Magazine About Medical Technology Innovations

#9 – New Care Solutions for Overweight

How a Small Implant Tells the Brain the Stomach Is Full


If diet, increased physical activity and medication do not sufficiently reduce weight in severely obese people, a new electronic device may help. The Maestro Rechargeable System by US-based EnteroMedics targets the nervous system and blocks vagus nerve signals between the brain and the stomach. Thus, it curbs hunger and makes a person feel full more rapidly.

The device for this “vBloc therapy” consists of a pacemaker-like electrical pulse generator with lead wires and electrodes. The pulse generator is implanted between the skin and the ribs and can be recharged wirelessly. The electrodes are surgically placed into the abdomen around the vagus nerve, which receives intermittent electrical signals from the pulse generator.

This nerve regulates a number of key stomach functions, including expansion, contraction and emptying into the intestine, thereby controlling digestion. It also informs the brain about the volume and macronutrient components in the gut, triggering feedback like “I am hungry” or “I am full.” If the nerve is blocked, the expansion and the contraction of the stomach is limited, leading to reduced appetite and an underlying sense of fullness.

The efficiency of the therapy varies

The FDA approved the device for obesity treatment based on data from a clinical study involving 233 patients with a body mass index (BMI) between 35 and 45. Additionally, patients had to suffer from at least one other obesity-related condition; such as hypertension or type 2 diabetes.

Researchers implanted a functioning Maestro Rechargeable System into 157 patients and an inactive implant into the control patients, and measured the loss of excess weight one year after surgery. Patients with an activated device lost 8.5 percent more weight than those with the dummy device.

Although the manufacturer hoped for 10 percent, about half the patients lost at least 20 percent of their excess weight, and 28 percent lost at least 25 percent. “Some patients lost 70 pounds. This is really a lot,” said Dr. Caroline Apovian, Director at the Nutrition and Weight Management Center at Boston Medical Center. “There exists more than one type of obesity and we have to find ways of figuring out which type of obesity is the best to treat with this device. But the results at 18 months are promising because patients with a sham operation regained weight and the patients being treated with the activated device did not.”

Acceptable risk-benefit

According to the manufacturer, more than 600 patients have received the implant so far. The vBloc Therapy can be deactivated, removed or reactivated.

Clinical studies demonstrated that it is not free of side effects. Researchers observed difficulties with swallowing, pain at the site of the device and in the stomach, heartburn, nausea, belching, and other problems. However, the underlying obesity also entails a number of risks, such as type 2 diabetes, stroke, heart disease, high blood pressure and sleep apnea.

Certain patients would accept vBloc’s risks in hopes of losing more weight, according to an FDA sponsored survey. “Eighteen million people in the U.S. have the indication for obesity surgery, but only 180,000 can have it. This means that 99 percent of this population needs help and doesn’t get it,” says Dr. John Morton from Stanford University Medical Center, current president of the American Society for Metabolic and Bariatric Surgeons (ASMBS). The costs of the vBloc therapy are comparable to those for other bariatric surgical procedures, more than ten thousand dollars. Therefore, only wealthier patients are able to afford it. But there are also other reasons such as patient preference and availability of surgery which limit current use.

From his perspective, the vBloc therapy is especially beneficial to people who would not typically seek other surgical treatments for obesity. “It is a very safe procedure and in comparison to the placebo, it leads to significantly more weight loss,” Dr. Morton says. On behalf of the ASMBS, which is currently reviewing all data from the FDA, he adds, “When we have complete data and the process is finished, we will come out with a recommendation.”

Competitors also target the vagus nerve

The market potential of the device seems huge given that more than one third of adults in the US are obese, as well as 10 to 30 percent in the European Union. However, EnteroMedics currently intends to commercialize the new device in the US only.

Competitors are using similar principles. The Ability Gastric Stimulator by the US company IntraPace, already approved in Europe, detects food and drink in the stomach via an implanted sensor and triggers a feeling of fullness.

An Israeli company created MelCap, a guided, disposable, ingestible capsule. An external magnetic field guides the capsule to a specific location in the stomach to target the vagus nerve.

The project i2move, led by researchers from the Imperial College of London, is focusing on an implantable device that also processes chemical signals.

And finally, the intestine also can be a target of electrical stimulation. The SatiSphere, a C-shaped device created by US-based Endosphere, is implanted into the duodenum to delay the passage of ingested food. It regulates appetite via a change in the release of hormones.
In the case of vBloc therapy, Dr. Apovian suggests combining it with anti-obesity medication and hopes that the BMI threshold for treatment can be lowered in the future

About the Author

Sabine Goldhahn is a freelance science journalist and medical researcher based in Switzerland.

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