For the first time experts have been able to eliminate external factors and specifically pinpoint television as having a direct link with female body ideals.

It is known that the perception of a woman's perfect body shape is influenced by images of celebrities and models seen in the media.

However, in the past, there has been little attempt to control variables in order to isolate the effects of media exposure from other cultural and ecological factors.

Scientists examined preferences for body size in relation to television consumption of men and women in Nicaragua, Central America. Findings are published in the British Journal of Psychology.

Research involved assessing groups with different levels of access to Western media. This included people from an urban area, a village with television access, and a village with little television access.

It was found that the highest Body Mass Index (BMI) preferences were found in the village with least media access, while those living in urban areas preferred thinner female bodies.

This study has implications for women's mental health and eating disorders in the UK as it provides further evidence of how the thin ideal promoted by the media creates body image dissatisfaction.

Dr Martin Tovee, a Reader in Visual Cognition at Newcastle University's Institute of Neuroscience, UK, co-led the research.

He said: "Our study shows that television is having a significant impact on what people think is the ideal woman's body.

"Nicaragua provides a unique opportunity to study media effects as we were able to minimise variance in potential confounding factors and focus on the influence of visual media.

"The differences in television access allowed us to explore how media exposure affects the size and shape women aspire to be.

"Findings revealed that the more television exposure people receive, the thinner a female body women and men prefer - the amount of media access directly predicts body ideals.

"Overall, these results strongly implicate television access in establishing risk factors for body image dissatisfaction."

The study was conducted on the remote Mosquito Coast of Nicaragua, in two villages of the Pearl Lagoon Basin.

The villages were selected because their inhabitants have differing access to electricity and to the media, while at the same time sharing similar environmental and cultural constraints.

More than 150 participants were recruited and identical data was gathered from men and women in each of the three locations.

All were tested individually and asked to identify how much television they watched. Those who had access to TV reported watching programmes such as soap operas, imported US films and music videos.

Images of women's bodies were shown and participants were required to rate them for attractiveness on a scale of one to five.

Data was recorded to indicate whether participants were trying to lose weight or not. Levels of dieting across the locations mirrored overall BMI preferences and levels of television consumption.

Body dissatisfaction is widespread amongst girls and young women in Western countries. Around 50% report being unhappy with their bodies, leading to low self-esteem, depression and eating disorders.

Dr Lynda Boothroyd, Senior Lecturer in Psychology at Durham University, UK, and co-leader of the study, said: "Internalisation of a thin ideal is a well-established risk factor for body dissatisfaction and eating disorders in the West.

"Our data strongly suggests that access to televisual media is itself a risk factor for holding thin body ideals, at least for female body shape, in a population who are only just gaining access to television.

"For now, most people in the rural sample still hold body ideals within the healthy range. However, the fact body shape ideals may mediate a link between television access and weight loss attempts in this population suggests we could potentially see the same kind of patterns play out here in the long-term as in the West."

Further studies will elaborate on the research to establish whether body ideals negatively affect psychological well-being, such as body esteem and eating attitudes.