Morgan Windram Geddes, a researcher at Dundee University, said young girls' view that "if they are thin they must be healthy" is putting them at risk of permanent health problems in later life.
She also believes Scots girls are shunning exercise as they believe sport is not feminine.
Ms Windram Geddes, a keen long-distance runner, believes a distorted message of health, based on the way you look, means girls are don't properly regulate their exercise or diet.
She studied girls aged 11-14 and found how beliefs about health are putting more and more girls off sport, while leading others to engage in unhealthy practices in their eating and exercise habits.
She said: "Encouraging people to exercise more and eat healthily is obviously a good thing, but our research shows that when the message is distorted it causes problems for young girls.
"Girls in the study are at an age when they are particularly body-conscious and mixed messages about diet and health can significantly compound the problem.
"We have a problem where there is one distorted message out there, and that is if you are thin then you are healthy, but this is not the case and young girls are making bad choices based on this message.
"On one hand you have girls who will over-eat, then over exercise to offset all the extra calories they have consumed.
"On the other side of this we have girls who are thin and think they don't need to exercise as they must be healthy already. People are only encouraged to exercise to lose weight, not for enjoyment or for more rounded health benefits.
"But the challenge we face is how to tackle preconceptions about fat and exercise and get across the message that a lot of the 'healthy' choices young girls are making are in fact damaging their health."