Botticelli's Venus is quite slender by the standards of Italian Renaissance nudes. Floating towards us on her shell, she seems perfectly proportioned. And she is. But what happens if you play around with a reproduction of this beloved painting on your computer and reduce her waistline to meet the demands of a modern catwalk or magazine? Italian artist Anna Utopia Giordano did – and the results, online at annautopiagiorani.it, are shocking and grotesque. They make you realise how remote in attitudes to the body the great nudes of art are from contemporary ideals of beauty, and how bizarre and limiting our own perspective is.

The original Botticelli Birth of Venus … those hips, that stomach! Photograph: Uffizi Gallery in Florence/Corbis

Some people would say that a painting like Titian's Venus of Urbino is a pornographic indulgence intended to gratify Renaissance princes in a coarse and carnal way. There is truth in that – when Titian was working on a later, even more sensual nude, the patron was assured it would "make the Venus of Urbino look like a nun". But if fleshly paintings are high-class erotica, this digital experiment shows they offer a far more inclusive, natural vision of the sexy than what is promoted in adverts and celebrity voyeurism today. As is obvious from the "skinny" version, the original Venus of Urbino has plenty of flesh on her. Titian's friend, Aretino, said Venetian men (such as Titian) love "tits and arses and sumptuous flesh".

As a matter of fact, there are Renaissance nudes that are just as skinny as any fashion designer could demand. The German painter Lucas Cranach the Elder portrayed strikingly thin and narrow-waisted nudes. His Venus believed you could never be too bony or wear too many hats. But he was a close friend of Martin Luther, and believed the body to be a vessel of sin. Those sensual Italians had a more abundant and generous idea of beauty.