Models' breasts have become gradually smaller, as have their hips, while waists have filled out. The overall result is a more androgynous look, say the researchers.

Over the years, Playboy centerfolds' body mass index has also decreased further below corresponding population levels. Their waist-hip ratio, however, is closer to the norm today than it was 50 years ago.

But boyish as these babes might be, the magazine certainly still has its finger on the pulse of what appeals to the men of today. Earlier this month, Playboy announced that it expects to report significantly improved 2003 results, almost doubling operating income over last year.

The holiday edition of the British Medical Journal is traditionally more flip than its usual fare. Other articles this year include a story titled, "Penalty Shoot-Outs Can Trigger Heart Attacks."