A real life-partner is often very different from an image a person builds of an ideal mate.
The study by researchers at the University of Sheffield and the University of Montpellier in France, found that our actual partners are of a different height, weight and body mass index than those we would ideally choose.
The study found that most men and women express different mating preferences for body morphology than the actual morphology of their partners and the discrepancies between real mates and fantasies were often larger for women than for men.
The study also found that most men would rather have female partners much slimmer than they really have.
Most women are not satisfied, either, but contrary to men, while some would like slimmer mates, others prefer bigger ones.
Human mating preferences are increasingly being studied to understand what shapes our complex reproductive behaviour.
Whilst previous studies have separately investigated ideal mate choice and actual pairing, this new research was specifically conducted to compare them.
The researchers gathered data from one hundred heterosexual couples living in Montpellier, south of France.
To measure preferences for body morphology, they used software, which allowed the participant to easily modify the body shape of their ideal silhouette on a computer screen.
The researchers then compared ideal silhouettes obtained with the actual characteristics of the partners.
For the three morphological traits studied - height, weight and body mass - men's mating preferences were less different from their actual partner's characteristics than females' ones.
As the authors remark, the lower dissatisfaction observed for men in this study may be restricted to some physical traits, and results could be different for other traits such as personality, political opinion or sense of humor that are also important in partner choice.
"Whether males or females win the battle of mate choice, it is likely for any trait, what we prefer and what we get, differs quite significantly. This is because our ideals are usually rare or unavailable and also because both sexes express preferences while biological optimum can differ between them," said Dr Alexandre Courtiol, from the University of Sheffield, who carried out the work with colleagues from the Institut des Sciences de l'Evolution de Montpellier.
The study has been published in the Journal PLoS ONE.