International Business Department           Liu Bojia           October 28, 2023

  One of the biggest difficulties for people trying to lose weight is keeping their mouths shut, and the first step to stopping eating is to feel full. Excluding the small percentage of people who will continue to eat even after they are full, many people will stop eating when they receive the signal that their stomach is full of food.

  The stretching of the stomach plays a key role in this process. Since the muscles under the gastric mucosa are highly extensile smooth muscles, the stomach continues to be enlarged and provide a stretching force as food enters. This force is sensed by cells with mechanoreceptors, and these signals are transmitted via the vagus nerve to the brain, which then stimulates the release of insulin, the appetite-regulating peptide PYY, and the hormone GLP-1, which work together to help the body digest food, reduce appetite, and increase satiety.

  Recently, a collaborative team of researchers from MIT, Harvard Medical School, and the University of Cambridge have been simulating the delivery of this stretching power message to make the brain mistakenly think it's full. The secret to this new method is a vibrating capsule. The capsule is safer and simpler to execute than implanting a gastric balloon in the stomach to produce a feeling of fullness. A related paper has been published in the journal Science - Progress.

  Back in the 1970s, an article in Science showed that vibration creates the illusion of stretching in skeletal muscle fibres. This also made the researchers wonder if vibrations could be used to trick the mechanoreceptors in the stomach into thinking that stretching had occurred, thus driving the feeling of fullness.

  For their study, they designed a miniature capsule that measures 31 millimetres long, which is about the same size as existing large capsule pills. But instead of a drug, this new capsule contains a vibrating element. Normally, this element would be prevented from activating by a spring-loaded spike attached to the gel.

  When the capsule enters the stomach, the gastric juices will dissolve the gel, at which point the vibrating element will start working properly, and the entire vibration time will last about 38 minutes, which is comparable to the amount of time it can remain in the stomach.

  For the application test, the authors selected 12 experimental pigs as test subjects. They would deliver vibrating capsules to the stomachs of the pigs in the experimental group, while a placebo capsule was used in the control group. The authors first detected a similar pattern of discharge from the nerves in the pig's stomach when the vibrating element was in effect, as when it was inflated by direct inflation, suggesting that the vibration was sufficient to elicit a stretch-related neural response in the stomach. At the same time, this vibrating capsule could cause changes in hormone levels in the pig during fasting that produced a meal, suggesting that it could affect brain function.

  And over a longer observation period, they recorded that pigs with vibrating capsules delivered in their stomachs ate less, consuming 40 per cent less food overall than the control group. While the capsules were in the pigs, the pigs did not show unusual side effects; the stomachs were neither inflamed nor did they produce vomiting or diarrhoea. There was also no need to worry about the capsule remaining in the body for long periods of time, as it was excreted in the faeces after about four days in the pig's body.

  The authors point out that the size of the capsule has reached the upper limit of the capsule size that can be taken, and that it might be a bit difficult to take it twice with a meal. But in addition, this approach is safer than existing therapies, such as the more popular GLP-1 therapy is not suitable for everyone, and there will be some side effects. The mechanical force-sensing method of generating a false sense of satiety will provide more options for the weight-loss community in the future.