The WearSens, a close-fitting metal necklace, is able to determine what a person is putting in their mouth by measuring the vibrations that occur as the food is swallowed and digested.

According to Popular Science, as a substance moves down the throat, it creates tremors that can be felt on the skin around the neck. The necklace's piezoelectric sensors are sensitive to mechanical disturbances and are able to record these vibrations.

There are distinct vibrations for different types of food. For example, there is a difference between the vibrations your body creates when eating something soft like mashed potato, and when eating crunchy food like a packet of crisps.

By monitoring these vibrations the device is able to determine how much food, as well as the types of food, a person is consuming. This information is then transmitted to the user's smartphone app.

The vibrations created can vary from person to person, so each individual device needs to be calibrated for its wearer.

"To personalise the device, we ask a new wearer to eat a 3-inch (7.6-centimetre) Subway sandwich and then sip down a 12-ounce (350-millilitre) drink," UCLA electrical engineer and co-developer Majid Sarrafzadeh told Popular Science.

According to a study published in IEEE Sensors Journal the device is able to distinguish between solid and liquid food 90 per cent of the time. The same study found the device could distinguish between hard and soft foods roughly 75 per cent of the time.

The device's website describes it as a "innovative wearable nutrition monitoring system", saying that it will offer "unprecedented visibility into individual nutritional wellness".

However, unpublished research has determined the WearSens could determine if an individual is smoking cigarettes or consuming pills, extending its benefit beyond nutritional management.