Klein, who wrote a book called "Moose: A Memoir of Fat Camp," said she was very popular at the weight loss camps she attended because she was thinner than many other children.
"All of the boys were flocking over," said Klein, adding that she also had her pick of girls to be friends with. "I suddenly felt beautiful and amazing and what a different world that was."
Kaslow also said factors that might contribute to social status -- including support at home, abuse and neglect, and ability to communicate -- are themselves strong indicators of later health outcomes because they influence behavior.
"If you're popular and other kids like you, you feel better about yourself and there's probably more support, so if stresses do happen in life, there are more people to help you deal with it," Kaslow said. "If nobody likes you, you are more likely to hang out or turn to eating bad foods and not take care of yourself."
Almquist said that the results remained consistent even after controlling for socioeconomic status, since that is known to correlate with ill health later in life. She reasoned this was true because, as a young person, social class is filtered through the parents, while social status among peers is a daily battle for many young people, and therefore, has greater impact.
But Dr. William Pollack, psychologist and director of the Center for Men and Young Men at McLean Hospital, pointed out that social class contributes to a person's origin, look and dress, all of which may influence how close peers want to be to a person.
Pollack did say these limitations may have been less important in Sweden in the 1960s than in the U.S. today.
Still, the study may push parents and educators to note how the social environment in a school may affect children and adolescents just as much as the academic environment, Pollack said. He urged adults to help reduce bullying and monitor who may be absent due to illness, complain to teachers, or get in accidents.
"We must be careful about how far one extrapolates [this data]... but there is decent evidence... that how kids rank themselves in middle school can have an effect on emotional well-being and physical well-being that is mediated by behavior years later," Pollack said.
"If we see a child left out, we can't say we don't have to do anything about that because that's how kids are. It makes us think twice."