Food lust

Although it is not clear exactly how hunger exerts an influence on attraction, past research suggests social, cultural and psychological factors are involved.

In some societies where food is a limited resource, such as the South Pacific, higher body weights are revered. In others where food is abundant, such as the West, lower female body weights are preferred.

Evolutionary psychologists believe this is a survival preference. What you are looking for in a mate is the best chance of healthy offspring and in an environment where food is scarce, a heavier woman is deemed a safer bet for this.

What can be regarded as a normal and acceptable body size is also influenced by what we see, including advertising, and can change. For example, migrants from rural to urban societies show an increasing idealisation of thinner figures.

Dr Viren Swami from University College London and Dr Martin Tovée from Newcastle University believe there are biological factors at work too.

Physical drives

Dr Tovée explained: "Your cognitive state, your drives and your interests are dependent on your underlying physiology, your blood sugar levels and your hormone levels and these depend upon hunger."

In the West, lower female body weights are preferred

They recruited male university students as they entered or exited a campus dining hall during dinner time.

They asked the men to rate how hungry they were on a scale of one to seven. Using these responses, the researchers selected 30 hungry and 31 satiated men to take part in the study.

The men were then asked to rate the attractiveness of 50 women of varying weights, all within a healthy range, who had been photographed wearing tight grey leotards and leggings.

The hungry men rated more of the heavier women as attractive than the men who were full up.

Dr Tovée said: "This shows how physiology does impact on our perceptions and thought processes."

He said the work also tied in with the resources model - in times of food scarcity, a heavier woman becomes the ideal.

Eating disorders

"Obviously we only saw a small shift in preference but it is a significant shift. If you were to extrapolate it onwards to people missing many meals and getting hungrier and hungrier over a longer period of time you might start to see a bigger shift."

They now plan to look at how hunger impacts on female attraction to males.

Dr Tovée said the findings might be completely different for women, particularly given the distorted body image perception of women with anorexia.

"Research suggests women's ability to judge not only their own but also other people's body shape is linked to their own body mass. As their body mass declines they tend to overestimate body mass. So the more weight they lose, the bigger they think they are."

The work could also help further our understanding of obesity, he said.

"A lot of what we are doing is looking at how flexible these representations of body size and shape are and the effect of environment. If you are growing up in an environment where you are seeing heavier body types, is this what you set your norm?

"We know that diet is related to social class and obesity tends to be class related too. So we are looking at how diet then impacts on your ideals and perceptions of what is a good or bad body shape."