The new underpants, from the Tokyo-based Goldwin company, claim that the average 10 stone man who walks 90 minutes a day while wearing them can lose 210 kilocalories weekly – the equivalent of half a litre of beer.

Key to the technology implemented in the underwear – which cost £23.52 (Y2,940) and are currently only on sale in Japan – is a resin which is printed on fabric to prevent it from stretching.

The extra muscle strength required to balance the tension in the resin during normal walking activities results in effortless loss weight, according to a spokesman for Goldwin.