Doctors are considering a new use for Botox: The drug may help obese people lose weight, according to early research.
The treatment may work by blocking a key nerve in the stomach that controls feelings of hunger and satiety, the researchers said.
In a small new study, researchers in Norway injected Botox into the stomachs of 20 obese people, who had body mass indexes (BMIs) ranging from 35 to 44. The researchers used a medical instrument called an endoscope to see inside the stomach and inject Botox into the lower portion of the organ. Patients received injections at the start of the study, and then once every six months.
After one year (during which the patients received two injections), 70 percent of the patients had lost weight; on average, they lost 17 percent of their excess body weight. After 18 months, when the patients had received three injections, 75 percent of the patients had lost weight; they lost 28 percent of their excess body weight, on average. (Excess body weight is the amount of weight in excess of a "normal" body weight, or a BMI of 25).
The researchers stressed that their study was small, and so more research is needed to confirm the results in a larger group of people. But if future studies verify the findings, then the procedure might become "another new way to treat obesity," said study co-author Duan Chen, a professor at the Norwegian University of Science and Technology, who presented the findings in San Diego Monday (May 23) at Digestive Disease Week, a scientific meeting focused on digestive diseases. [7 Conditions That Botox May Help Treat]
Several previous studies also tested whether Botox could help with weight loss, but most of these studies found that Botox didn't help people lose weight. However, those earlier studies followed patients for only a few months after a single Botox injection, whereas the new study followed patients for more than a year with repeated Botox injections, Chen said.
In addition, researchers in earlier studies assumed that Botox, which relaxes muscles, would help people lose weight because it would slow down the rate that the stomach empties itself. But the researchers in the new study tested a different theory: whether Botox could block the vagus nerve, which connects the brain and the stomach and controls feelings of hunger and satiety.
First, the researchers tested their theory in animals, by targeting the vagus nerve with Botox in rats, and found that the rats ate less and lost weight. However, in experiments where the rats had their vagus nerve cut, they didn't lose weight with the Botox injections, suggesting that Botox was acting through the vagus nerve to induce weight loss, the researchers said. This prompted the researchers to target the vagus nerve with Botox in people.
"It really was a new technique, [using Botox] to block the feedback between the stomach and the brain," Chen told Live Science.
The drug is relatively safe, and patients did not experience serious side effects in the new study or in previous studies of Botox for weight loss, Chen said. It is also a quick procedure, taking about 15 minutes, he said.
Still, in rare cases, Botox can cause serious side effects, including muscle weakness, double vision and trouble breathing, according to Allergan, the makers of Botox. The drug may spread from the injection site and affect other areas of the body, but this has only happened when Botox was not used as recommended, the company says.
The new study was funded by the European Commission and The Liaison Committee between the Central Norway Regional Health Authority and the Norwegian University of Science and Technology.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.