A new body serum that claims to boost women's cleavage by as much as three-quarters of a cup size in just four weeks has become a hit in the UK market. The 'boob job in a tube' works by stimulating the formation and storage of naturally occurring fat cells in the breasts, thus boosting the size, the Daily Mail reported. The Bust Fix serum developed by the UK company, NIP + FAB, is flying off the shelves at a rate of 1,000 tubes a minute at its peak and, in the last fortnight alone, sold 100,000 in Boots stores nationwide and online. The bust serum uses an ingredient called mangosteen, taken from the skin of the fruit, to prompt the production fatty acids in the breast tissue. It also 'plumps up' and enlarges the fat cells, which already exist to more than 100 times their size. The serum, which cost 16.29 pounds, differs from rival collagen-boosting creams that tend to target the skin around the bust - rather than the fat stores under the skin -- to lift and plump up the breasts. In independent trials on 6,000 women, two-thirds of women saw an increase of half a cup size after 12 weeks, while almost a quarter went up by three-quarters of a cup size. Tests by dermatological scientists found the Bust Fix increased the production of fatty acids, a process known as lipogenesis, by 57 per cent in five hours. The cream also uses plant ingredients such as green algae and quince-hydrogel to firm and lift the breasts. NIP + FAB said the serum "provides essential nutrients to the bust" to improve the skin's elasticity and thus help to smooth and lift the breasts. During trials, 85 per cent of women agreed that it "visibly plumped, smoothed and firmed the skin" around the bust and neckline.