Saturday, January 06, 2007

Magazines, Teens, and Dieting, Part II

In a previous post, I mentioned that I would revisit the news that reading diet articles leads to unhealthy food behaviors in teens when I had a chance to read the entire study.

Citation: van der Berg P, Neumark-Sztainer D, Hannan PJ, Haines J. Is dieting advice from magazines helpful or harmful? Five-year associations with weight-control behaviors and psychological outcomes in adolescents. Pediatrics. 2007 Jan;119(1):30-7. [Abstract]

A Summary
Who Was Included
Middle/junior high and high school students in Minnesota public schools who were in grades 4-7 at the time of the survey (1998/99 school year). Follow-up with participants (the students) occurred during the 2003/04 school year (5 years after the original surveys and measurements).
Note: When I refer to "reading" below, I'm referring specifically to reading of diet/weight loss-related magazine articles.

What Was Done
In 1999, middle and high school students completed in-class surveys (see below) and had their weight and height measured, from which a BMI was calculated. 5 years later, the students were contacted by mail to complete a revised version of the original survey, but were not weighed and measured a second time.

What the Survey Asked About
  • "How often do you read magazine articles in which dieting or weight loss are discussed?" - Students could choose never, hardly ever, sometimes, or often.
  • "During the past 6 months, how important has your weight or shape been in how you feel about yourself?" - This was intended to assess the importance of weight to the students, who could select choices in a range from "Weight and shape were not very important" to "Weight and shape were the most important things that affected how I felt about myself."
  • To assess weight related behaviors, students were asked (as yes or no questions), "Have you done any of the following things to lose weight or keep from gaining weight during the past year? Responses that were considered healthy were: exercised; ate more fruits and vegetables; ate less high-fat foods; ate less sweets. Responses that were considered unhealthy were: fasted; ate very little food; used a food substitute (powder or a special drink); skipped meals; smoked more cigarettes. The following responses were considered estremely unhealthy weight control behaviors: took diet pills; made myself vomit; used laxatives; used diuretics.
  • To assess binge eating, students were asked two questions: "In the past year, have you ever eaten so much food in a short period of time that you would be embarrassed if others saw you (binge-eating)?" and "During the times when you ate this way, did you feel that you couldn't stop eating or control what or how much you were eating?"
  • Students also completed scales measuring body satisfaction, depressive symptoms, and self-esteem, and provided information such as race, age, and gender.

    Findings
  • 2516 students completed both the initial and the follow-up surveys, 1130 males and 1386 females responding.
  • "Overall, female adolescents were significantly more likely to be frequent readers of dieting/weight loss magazine articles (44%) than were male adolescents (14%; P < .001), and older female adolescents were more likely to be frequent readers than were younger female adolescents."
  • Among females: There was no significant difference in weight related to reading status. White and Asian females were most likely to report frequent reading of diet/weight loss magazine articles.
  • Among males: Whites and Native Americans reported the least frequent reading. Males with heigher weights were more likely to report reading.
  • No significant association was found between reading frequency and psychosocial measures (such as depression and self-esteem).
  • The meat of the results:
    "For female adolescents, the odds of engaging in healthy, unhealthy, and extremely unhealthy weight-control behaviors at time 2 increased with increasing frequency of time 1 magazine reading, after adjustment for age, race/ethnicity, cohort, SES, time 1 BMI, time 1 weight importance, and time 1 levels of dependent variables (Table 2). For healthy weight-control behaviors, female adolescents who reported "hardly ever" or "sometimes" reading magazines had 1.6 and 2.4 times the odds of engaging the behaviors compared with the reference group of nonreaders, but no significant increase in odds was found for female adolescents who reported "often" reading magazines. Girls who reported magazine reading had between 1.6 and 2.0 times the odds of engaging in unhealthy weight-control behaviors, compared with nonreaders of magazine articles about dieting or weight loss, in adjusted analyses (Table 2). Likewise, for extremely unhealthy weight-control behaviors, frequency of magazine reading had a strong positive association with the odds of engaging in unhealthy behaviors at time 2, with ORs ranging from 2.3 for female adolescents who reported "hardly ever" reading magazine articles to 3.2 for those who "often" read magazine articles. A marginally significant, ordered association was found between binging and magazine reading for female adolescents. For male adolescents, the analyses revealed no consistent patterns and no significant associations between magazine reading and any of the weight-control behaviors or binge eating."
    What That Last Finding Says, In Plain English
    Female teens who reported reading more frequently on the first survey were more likely to engage in healthy, unhealthy, and extremely unhealthy behaviors 5 years later. So, some girls who read more articles engaged in more healthy behaviors than nonreaders or less frequent readers, while other girls who read more engaged in more unhealthy behaviors.

    Commentary
    A few things come to mind when reading this study. First, the survey questions do not seem to reflect the full range of possible weight-related or eating behaviors. For example, exercising is considered a healthy behavior by the authors, but they do not assess the amount of exercise, possibly ignoring behaviors that are not truly reflective of health, such as compulsive exercising, sometimes referred to as "exercise bulimia." It is also not clear that the students were provided with examples or information that would have helped them make choices about items such as eating foods that are lower in fat - it is not clear whether the students were able to accurately assess their behavior in order to answer these questions. The questions don't seem to address the severity of behaviors, either. Students were asked whether they had ever in the previous year skipped a meal, smoked more cigarettes, used a laxative, etc. in order to lose or avoid gaining weight. There is likely a vast gulf between the student who remembers skipping a meal or two in the past year and one with regular unhealthy behaviors. Respondants also had some wiggle room in the extreme behaviors category - asking solely about diet pills and forced vomiting permits students who may be using illegal drugs, eating solely foods with no fat, or completely refusing to eat from having to acknowledge an extreme behavior and being counted as such by the researchers. Finally, there does not seem to be a definition provided of the reading frequency - "often" may be every day to one person, and once a month to another. As a result of these study design issues, the researchers may have overcounted disordered behavior in some instances, and undercounted it in others.

    Additionally, the authors did not ask about the specific magazines the adolescents were reading, or what subjects were covered in the articles they remembered as diet/weight loss-related. For the purposes of this study, the number of diet/weight-related articles remembered by teens as coming from Cosmopolitan or Seventeen or Ms. Magazine or a specialized sporting activity magazine would be counted exactly the same. Similarly, the magazines the teen girls and boys were reading may have been very different in tone and approach to the body.

    The authors are also not able, based on their study design, to prove that reading magazine articles has any direct cause of disordered eating behaviors, or even healthy ones. They simply find that the two may be associated in some cases. It is entirely possible that the girls with healthy behaviors were self-selecting articles that supported a healthy viewpoint, or reading articles because they had an interest in fitness. It is also possible that those with extreme or unhealthy behaviors were already concerned about body image, or were generally concerned about appearances, and that is why they were reading those articles in the first place. What we cannot tell from the study is whether magazine-reading influenced the girls, or whether some already existing characteristic of the girls (perhaps predisposing them to certain eating behaviors) influenced them to read the magazine articles.

    The Bottom Line
    Mass media may possibly influence adolescent eating and weight behaviors, but this study doesn't, and can't, prove it. Headlines such as "Reading Diet Articles Could Be Unhealthy" (as the NYTimes titled their piece) are somewhat misleading, because the study also found healthy behaviors associated with magazine reading.

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    MeSH Tags: Adolescent; Adolescent Behavior; Body Image; Mass Media; Periodicals
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