Possessing a 'figure 8' body has long been a trademark of feminine beauty, and now new research has revealed the reason why men tend to prefer women with a waspish waist.

The study also linked the middle proportion of a woman's body to the likelihood of satisfaction and erectile dysfunction in her partner.

Researchers found that the slimmer a woman's waist, the more satisfied her partner and the less likely he is to suffer impotence in the bedroom, according to the study published in the journal Archives of Sexual Behavior.

Past studies have found that men generally perceive slimmer women as more sexually attractive. Researchers explained that in terms of evolution, humans are programmed to associate overweight people with an increased risk of health problems, therefore a woman with a slimmer waist is perceived to be healthier and to have a greater chance at reproductive success.

To study the link between women's waist and her perceived sexual attractiveness to her partner as well as their overall sexual satisfaction, researchers measured a man's sexual function using an established questionnaire called the International Index of Erectile Function.

Researchers also recorded how often the 699 study participants - Czech men between the ages of 35 and 65 years old - had sexual intercourse.

The study revealed that men who suffered the least performance issues were younger, had younger partners and partners with slimmer waists. Researchers added that these men were also more satisfied with their sex life.

What's more researchers said it was "noteworthy" to point out a slender waists were linked to better erectile function, greater frequency of penile-vaginal intercourse and greater sexual attraction independent of both partners' age.

Lead researcher Stuart Brody, professor of psychology at the University of West Scotland said that there were two possible explanations for the "waist effect".

The first reason was that woman's abdominal body fat decreased their own sexual desire on a hormonal level, which would hamper libido.

The second reason could be that men simply found slimmer women more attractive and thus had fewer problems in the bedroom.

"The most compelling explanation was that slimmer women are, on average, more sexually attractive to men (resulting in more frequent sex, stronger erections, and greater satisfaction)," Brody wrote in the study.

"This is not surprising, given evolutionary selection pressures, because accumulation of excess body fat, especially abdominally, is associated with elevated risk of metabolic, cardiovascular, and neoplastic disorders (Singh, 2002)," he explained. "The elevated risk of such disorders could result in poorer fitness and hence less desirability as a mating partner."

Researchers noted that the recent findings do not only apply to women, after they found that that the larger a man's waist size, the lower his sexual satisfaction.

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