Researchers in Britain say they have found that people often choose partners with similar body fat levels as themselves.
A team from Aberdeen University and the Rowett Research Institute in Scotland conducted a study involving 42 couples and discovered that people often choose partners with similar body fatness to their own as well as within their own social class.
The Aberdeen team say people also consider looks, height and race but they have also found those with about the same amount of fat are likely to be attracted to each other.
The scientists suggest that this "assortive mating" could be a factor in the worldwide obesity epidemic.
As a rule people now settle for their life partner later in life often in their mid to late thirties and also start families later.
Problems of overweight and obesity are becoming evident at a much younger age and children who have an overweight mother and father are possibly more susceptible to being overweight themselves.
The researchers measured the body composition of the 42 couples and found the amount of body fat in one person was proportionately very similar to that of their partner.
They measured the body fat using DXA (dual-energy X-ray absorptiometry), which is a much more accurate and reliable method of assessment than BMI.
Professor John Speakman, of Aberdeen University, says it is unclear how these associations come about and he speculates that the social activities of the overweight and obese people coincide, making them more likely to meet partners who are also overweight and obese.