affect consumption behavior. Other studies have shown that the media can promote sedentary behaviors, such as television watching, that may adversely affect energy balance (Gortmaker et al., 1996, 1999; Robinson, 1999; IOM, 2005; Epstein et al., 2008). Poor eating habits and sedentary behaviors shaped during childhood and adolescence may be carried into young adulthood and continued into pregnancy, with the potential to affect GWG indirectly. Moreover, by influencing energy balance over the long run these habits and behaviors may also have an impact on prepregnancy body mass index (BMI) as well as other biological determinants of GWG.

Not all media influences are negative. Media can be used to convey consumer information and public health messages, such as those regarding youth smoking, and seat belt and child car seat use. However, social marketing programs that use the media to promote physical activity or healthy diet in adults, whether as part of a mass media-focused effort or a broader multi-component campaign, tend to produce mixed results. The most successful social marketing programs have had higher funding, have been better sustained, and were shaped by formative research (IOM, 2006).

Culture and Acculturation

Although it is plausible that cultural norms and beliefs may influence dietary behavior and physical activities, thereby affecting energy balance and GWG, the committee was unable to identify studies that examined specifically the effects of culture and acculturation factors on GWG. For example, it is widely believed by women of all ages, ethnic groups, and income and education levels that the consumption of certain foods marks a child before birth, which may then lead to certain food preferences and avoidances (IOM, 1992; King, 2000). As another example, most women know that low GWG will produce a small infant, which will be delivered more easily than a larger one. In some cultures this knowledge may encourage women to “eat down” in late pregnancy in order to avoid a difficult birth (King, 2000).

Acculturation, the process in which members of one cultural group adopt the beliefs and behaviors of another, is often associated with adoption of unhealthy behaviors, including food choices. Using nativity or duration of residence in the United States as a proxy for acculturation, several studies have found greater rates of overweight and obesity among children and nonpregnant adults who are more acculturated, compared to their less acculturated counterparts (Lizarzaburu and Palinkas, 2002; Hubert et al., 2005; Hernandez-Valero et al., 2007; Fuentes-Afflick and Hessol, 2008). For example, in a population-based study of 462 mothers in California, Schaffer et al. (1998) found that in the 3 months before pregnancy, foreign-born Latinas had the lowest contribution of fat to total energy intake and the highest dietary intake of carbohydrate, cholesterol, fiber, grain products,



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