How a vibrating capsule could help curb obesity

Obesity is a common and serious disease in the United States, affecting two in five people. When someone is obese (a body mass index of 30 or higher), their weight is unhealthy, which increases the risk of type 2 diabetes, heart disease, stroke, and certain types of cancer. 

Current weight-loss options include diet and exercise, which in some cases are unsuccessful, FDA-approved appetite suppressant drugs with known side effects, and invasive procedures such as bariatric surgery, which requires long-term lifestyle changes. 

A team of scientists at the Massachusetts Institute of Technology (MIT), Brigham and Women’s Hospital, and Harvard University have developed a noninvasive alternative—an oral capsule containing a tiny vibrating motor that is designed to stimulate the stomach to produce the same sense of fullness people experience after eating a large meal.  

In a preclinical animal study published in Science Advances, the researchers found that when pigs were given the vibrating electronic capsule before meals, they had significantly reduced food consumption and slower weight gain compared to when they didn’t receive the treatment. 

“The metabolic responses triggered by the ingestible capsule have the potential to benefit people struggling with obesity. By simulating fullness, this capsule could facilitate weight loss and better glycemic control,” said Dave Rampulla, Ph.D., director, NIBIB’s Division of Discovery Science and Technology. 

An artificial feeling of fullness     

Previous research has shown that applying external vibrations to a muscle tendon can create an illusory sense of movement. The researchers wanted to test whether applying vibrations in the stomach could trigger an artificial feeling of fullness.    

“We wanted to explore whether we could use the body’s own sensory feedback mechanisms to create a sense of fullness in the stomach. Our proof-of-concept study examined whether vibrations would induce and stimulate stretch receptors in the stomach, enabling the stomach to distend and send signals to the brain that create an illusory sense of fullness,” said lead author Shriya Srinivasan, Ph.D., an assistant professor of bioengineering at Harvard University.

To test the concept, the research team designed a capsule containing a small battery-operated device with a vibrating motor and a gelatinous membrane that will dissolve in human stomachs when it mixes with gastric juices. The vibrations activate stretch receptors in the stomach in the same way as when we eat. This sends a signal to the brain to initiate the hormones that help us digest our food, feel full, and stop eating. 

Evaluation in a large animal model

The researchers evaluated their vibrating capsule in a swine model because their gastric anatomy is similar to that of humans and biomedical gastrointestinal devices have been evaluated in swine before.  

To assess how the capsules affected appetite and the amount of food consumed, the researchers designed an experiment with four pigs. The scientists compared how much each pig ate for two weeks with the vibrating capsule and how much each pig ate for two weeks without the vibrating capsule. During treatment, the vibrating capsule was activated before each meal for 30 minutes. The results showed that, on average, the four pigs ate 40% less food when treated with the capsule. The intake for a given meal was the proportion of the food consumed in the first 30 minutes. 

The researchers evaluated whether the vibrating capsules affected weight gain. They found that the treated pigs gained weight more slowly than the untreated pigs. Their body weight was measured at least twice a week during the study, although the researchers didn’t quantify the results. 

The researchers also evaluated the effects of the vibrating capsules in fasting swine on the hormones involved in digestion, feeling full, and appetite. Six swine were treated with the capsules and six different swine received a “sham” (placebo) pill. Blood samples revealed that the treated animals experienced a marked reduction in the hunger hormone ghrelin compared to the untreated animals. This decrease represents a reduced appetite, which facilitates weight loss. 

The safety of the vibrating capsules was also assessed in the treated swine and no adverse effects were reported. Other experiments showed that the capsules took four to five days to pass through the animals’ digestive tracts.

The main study limitations were related to using a young swine model for laboratory research. The researchers said that it was challenging to quantify their weight loss and plan to study the vibrating pill next in other animals with similar stomach geometry to humans’. 

“Following further safety validations, clinical translation could facilitate a paradigm shift in potential therapeutic options for obesity and other diseases affected by late stomach fullness, which leads to excessive overeating and subsequent metabolic, cardiac, and endocrine conditions,” said senior study author Giovanni Traverso, M.D., Ph.D., an associate professor of mechanical engineering at MIT and a gastroenterologist at Brigham Women’s Hospital.

This research was supported in part by a grant from NIBIB (R01EB000244). 

This science highlight describes a basic research finding. Basic research increases our understanding of human behavior and biology, which is foundational to advancing new and better ways to prevent, diagnose, and treat disease. Science is an unpredictable and incremental process—each research advance builds on past discoveries, often in unexpected ways. Most clinical advances would not be possible without the knowledge of fundamental basic research.

Study Reference: Shriya S. Srinivasan et al. A vibrating ingestible bioelectronic stimulator modulates gastric stretch receptors for illusory satiety. Science Advances: 2023. 9, eadj30039. DOI: 10.1126/sciadv.adj3003