The Wonderfit yo-yo jeans that will fit you on fat days This won't be you anymore! Picture: Supplied Source: Leader The Wonderfit jeans in all their glory. Picture: Asda BUYING clothes when you are trying to lose a few kilos is always a tricky business. Should you buy for the size you are, or the size you want to be? Now, the folks behind the UK clothing line George at Asda claim to have come up with a solution. They are introducing jeans designed to shrink as you slim - or expand as you, well, expand. The supermarket chain's Wonderfit jeans are made from ultra-stretchy elastane, a similar fabric to that used in control underwear. In theory, this means they can span three dress sizes - so a 'small' should fit a woman who is size eight, ten or 12, while 'medium' can be worn by a size 14, 16 and 18 and 'large' should fit dress sizes 20, 22 and 24. The jeans, launched yesterday in stores and online, cost £18 ($26) and are available in blue and black. And given that the average woman owns ten pairs of jeans, four of which are never worn because they no longer fit, it seems the designers could be on to a winner. Fiona Lambert, brand designer at George, said: 'We've all had days where we struggle to button up our favourite pair of jeans, or days when our favourite jeans are a little looser following weight loss. With Wonderfit jeans, gaining or losing a few pounds will make no difference... they're a solution for many women across the nation whose weight tends to fluctuate regularly.' The retailer will be hoping their latest offering will be as a big a hit as their 'Great Bum' jeans, which sold 100 pairs a minute after they were launched in 2011. Six months ago, they added 'Great Bum and Tum' jeans to the range - claiming they could flatten stomachs, flatter bottoms and smooth away love handles thanks to a high, curved waistband and inner support panel that ensured any wobbly bits were held within the trousers. Unfortunately, Asda ship to Europe but not Australia - might be time to enlist the help of your UK-based friends!