Although a high waist-hip ratio most commonly goes with being overweight, it can also be found in women of normal weight who have high testosterone levels - a condition that is also associated with being hairy, infertile and having a 'male' body shape.
The view that men are attracted to a variety of female physical attributes and that there is therefore no single ideal woman does not find favour with Professor Singh.
This is another reason why women who are seriously underweight often stop menstruating - they would not have the resources to support a pregnancy or a baby.
But according to a new theory, the secret of sex appeal lies in the waist - or, to be precise, the waist- hip ratio calculated by dividing the waist measurement by the hip size.
The smaller the waist in relation to the hip, the more desirable a woman is seen to be.
Absolutely any female who seems young, healthy and fertile will set us off - and there seems plenty of evidence for that, too.
Then there are the amateur votes for anything from hands to earlobes.
American males, it has been calculated, spend some $3 billion a year to gaze at women with hourglass figures, those whose small waists blossom into sinuously curvy hips.