Just wondering, how do stars keep unnaturally thin for so long??

I was looking at pics of Victoria beckham when she was younger. she was about 11 stones and she now says that she has a naturally high metabolic rate. lol. just what do these peolpe eat to stay size 0? I did it as a teenager and could not maintain such a low body weight and gave up. i have since matured and prefer health, but what do they eat and how do their bodies not force them to binge