Watching stick-thin female frames on television can have an impact on women's health, according to a new scientific paper.
Dr Aric Sigman claims that seeing women on screen who are underweight but perceived as "normal" can be harmful to girls and women.
He said a biological mechanism which makes females become unhappy when they look at images of an abundance of underweight women has been identified.
The relationship between media and body image was previously treated as a psychological or cultural debate but now it must be treated as a medical one, said Dr Sigman.
"This is a medical and profound message. It is harmful to British girls and women," he said.
Dr Sigman, who has collated research from across the globe for a paper in The Biologist, the journal of the Society of Biology, said that studies have found "strong and immediate" brain changes in confident and healthy women when they are exposed to images of thin and fat females.
He said if a researchers told the women they looked like an image of a bigger woman they found a reaction in the medial prefrontal cortex - the part of the brain associated unhappiness and sometimes self loathing.
Another study looked at a different part of the brain - the amygdala - which is associated with strong emotional reactions such as fear, threat and anxiety.
"They found it was significantly activated in healthy women when they were shown an image of themselves which was doctored to look a little bit wider," said Dr Sigman, a fellow of the Society of Biology.
"A similar reaction occurred when women were shown words on screen such as obesity or fat"
