Fiona MacRae

Last updated at 16:55 08 August 2007

Some fall for beautiful eyes while others are smitten with a smile.

But when it comes to deciding on true love, you might be better off looking at your intended's waistline.

Scientists have shown that we tend to marry partners with a similar level of body fat to our own.

Flab, or the lack of it, is just as important as background, class or age in determining who we choose to spend our lives with.

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It is thought the phenomenon - known as assortative mating - could be a key factor in Britain's growing obesity problem.

Adult obesity rates have nearly quadrupled over the last 25 years, making this the second-fattest nation in the developed world, trailing behind only the U.S.

Children of overweight couples are likely to inherit genes that make them prone to putting on weight too, and so be more likely to have a weight problem themselves-according to the researchers-from Aberdeen Universityand the Rowett Research Institute.

"If someone who is overweight or obese gets together or marries someone who is overweight or obese, their children could have a genetic disposition to obesity," said one of the researchers, Dr Diane Jackson.

The study, published in the American Journal of Clinical Nutrition, found body scans of 42 couplesshowed they shared similar levels of body fat.

The finding held true even when factors which can influence weight, such as age and class, were taken into account.

The study also showed that rather than couples simply growing fat together, they actually started off that way.

"In the 1940s and 1950s, people mostly got married in their early twenties before they were overweight or obese," said researcher Professor John Speakman.

"So it would have been difficult for them to assortatively mate for body fatness because it would have been impossible to distinguish somebody who was thin from somebody who was thin but going to become fat.

"Nowadays, we choose partners and have children much later, but if we are going to become obese, on average we do so much younger.

"This makes it possible for potential partners to select each other on the basis of body fatness.

What is currently unclear is how these associations come about.

Perhaps the social activities of the overweight and obese people coincide, making them more likely to meet partners who are also overweight or obese.

Recent research has shown that the company we keep has a huge effect on our weight.

Those with fat friends are almost three times more likely to become obese themselves.

Why women don't trust a handsome hunk

If fairy tales are to be believed, a girl can't do better than a tall, dark, handsome stranger. Reality, however, begs to differ.

Research shows that women dismiss macho types as being cold, domineering and with a roving eye. And bad fathers to boot.

In contrast, more feminine-looking men are regarded as warm, caring and committed - and ideal daddy material.

The researchers, from St Andrews and Durham universities, asked more than 400 men and women to rate a selection of male faces, which had been digitally altered to look more masculine or feminine, on whether they appeared to be ambitious, domineering, faithful, warm or a good parent.

The analysis showed that both sexes regarded the classic hunks as the big losers.

Dr Lynda Bothroyd, who led the research, said: "This shows agreement between women about what they see, personality wise, when asked to judge a book by its cover."