A curvaceous behind is in high demand as celebrities tout their booty – but what exactly is involved. Dr A Bolin finds out from plastic surgeon Naveen Cavale.   It may not have made it into the top ten list of most performed procedures in the UK but the popularity of a ‘butt lift’ is rising. The likes of Nicki Minaj, Kim Kardashian,  Beyonce and J. Lo, have put curves back in fashion. Some celebrities openly discuss what nips and tucks they have undergone while others mysteriously become more voluptuous vowing they have not had any work done. Either way,…