Obesity in adolescents and young adults is a major public health problem with numerous consequences in adolescence and adulthood. During the past three decades the prevalence of obesity among adolescents has increased markedly, with recent estimates as high as 17% for adolescents and 28% for young adults (1
). There is evidence that being obese in childhood and adolescence at least doubles the risk of obesity in adulthood, (3
) and some studies have shown that the most obese adolescents have a seventeen-fold greater chance of becoming obese adults when compared to their non-obese peers (4
). Moreover, obese adolescents are 30% more likely to die prematurely compared to their normal-weighted peers, although this is largely explained by their increased risk for adult obesity (5
The burden of obesity is currently greater within certain racial and ethnic groups in the United States. Among females, this disparity is most pronounced in African-Americans and some Hispanic subpopulations (2
). In the most recent National Health and Nutrition Examination Survey (NHANES), Ogden et al. found non-Hispanic Black girls were twice as likely, and Mexican American girls were 1.5 times as likely, as non-Hispanic White girls to be obese (1
). In another NHANES study, 50% of Black women ages 20–39 were obese, compared to 36% of Mexican American women and 24% of White women (2
). There is evidence that this disparity starts early (9
). Kimm, et al found an increase in the difference in median Body Mass Index (BMI) between White and Black girls from 0.4 to 2.3 kg/m2
during the ages of 9 and 19. (10
) This race difference is particularly worrisome since Black girls who are obese in childhood and adolescence are more likely than obese White girls to remain obese as adults (9
Health behaviors, such as dietary intake, physical activity, and inactivity, have been a major area of focus in trying to understand the origins of obesity. Television viewing has been one of the health behaviors most consistently associated with obesity (12
). In their seminal paper linking television and obesity in children and adolescents, Dietz and Gortmaker note that this relationship may be mediated by a direct displacement of physical activity, as well as an increase in caloric consumption induced by food advertisements and snacking time (14
). Although television viewing is often associated with lower levels of physical activity among girls (12
), it appears to have an independent relationship with weight status even after controlling for levels of physical activity (17
). Furthermore, several studies show a stronger correlation between obesity and inactivity, including television viewing, than obesity and physical activity (18
). While the association between television viewing and weight status has been found in both genders, the relationship appears stronger and more consistent in females (17
There is evidence that adolescents and young adults from racial and ethnic minority groups watch more television (7
) and are less physically active(7
) than their white peers. Despite these consistent findings, several studies of pre-adolescent to young adult females have found that television viewing and weight are not statistically related in Black girls. (16
) In fact, the lack of a relationship between television viewing and BMI among Black girls may be one reason why some studies of television and obesity using racially heterogeneous populations have had null findings (16
). The reasons why television and weight are not as consistently related in females from racial and ethnic minority groups as they are in White females is not well understood.
Prior studies of how race and ethnicity affect the relationship between television and obesity have often been small, localized to a few cities, and/or focused only on adolescents. The National Longitudinal Study of Adolescent Health (Add Health) offers a unique opportunity to add to the current literature on ethnic and racial differences in television viewing and obesity because it contains data from over 7,000 young women from a variety of race/ethnic groups surveyed both in adolescence and in young adulthood. The study includes a wealth of information on personal and socioeconomic backgrounds and health behaviors. Although Add Health has information about additional forms of inactivity, such as listening to the radio and/or playing computer games, we opted to focus exclusively on TV because of its potential to impact weight status through multiple pathways such as involving the participant in a sedentary behavior or inducing increased snacking through exposure to advertisments for calorie dense foods. We also felt that TV watching was less likely than other forms of media to be done concurrently with other activities (i.e. running while listening to a portable music player, playing an active video game such as Dance Dance Revolution).
We used Add Health to address the following hypotheses: 1) Increased television viewing is associated with higher average BMI in young adult women; and 2) The association between TV viewing and BMI will be different in White young adult females when compared to both Black and Hispanic young adult females.