The prototype contains removable sensors that monitor heart and skin activity to provide an indication of mood levels.

The aim was to find out if wearable technology could help prevent stress-related over-eating.

Mood data was provided to the wearer via a smartphone app in order to highlight when "emotional eating" was likely to occur.

A team from Microsoft's visualisation and interaction research group embedded an electrocardiogram and electro-dermal activities sensors as well as a gyroscope and accelerometer in the bra.

In their paper, the researchers say using a bra "was ideal because it allowed us to collect EKG [electrocardiogram] near the heart".

Efforts to create a similar piece of underwear for men worked less well, largely because the sensors were located too far away from the heart.

The women testing the technology reported their emotions for about six hours a day over a period of four days.

"It was very tedious for participants to wear our prototyped sensing system, as the boards had to be recharged every three to four hours," Microsoft senior research designer Asta Roseway said.

Electric shock

Wearable technology is increasingly being used to monitor a range of health conditions.

Last month saw the release of a Twitter-connected bra, that tweeted every time it was unhooked to encourage women to self-examine their breasts.

And last year a patent was awarded to a US firm that was working on a wearable device that analysed breast heat in order to detect cancer.

Meanwhile in response to a series of rapes in India, three engineering students developed a bra loaded with sensors and an electronic circuit that is activated when someone attempts to grope a woman wearing it.