Emerging Adulthood and College‐aged Youth: An Overlooked Age for Weight‐related Behavior Change

Abstract

Obesity is a major public health concern, and effective population-wide intervention strategies aimed at reducing obesity are needed. Although a growing body of literature has explored modifiable determinants of excess weight gain in adults and, to a lesser extent, in children, other important ages have been understudied. Though once considered to be an age of optimal health and well-being, the transition from adolescence to young adulthood is gaining recognition as an important time for health promotion and disease prevention. Not only is the presence of obesity and unhealthy lifestyle characteristics at this life stage associated with increased chronic disease risk, but this also may be a critical time during which young people establish independence and adopt lasting health behavior patterns. The objectives of this article are to: (i) describe emerging adulthood as a developmentally unique life stage, (ii) highlight epidemiologic evidence documenting adverse changes in diet, physical activity, and weight during this stage, (iii) discuss the influence of food and beverage marketing targeting emerging adults, and (iv) illustrate the need for health promotion and intervention efforts that could target young adults through settings such as postsecondary institutions. Over the past 50 years, major population-level demographic shifts including increases in postsecondary education and delays in marriage and childbearing have occurred. These shifts have opened the door for a period of “emerging adulthood,” typically defined as 18–25 years of age (1). This period is marked by important transitions such as leaving home and increasing autonomy in decision-making; however at the same time, adult responsibilities such as financial independence and residential and employment stability are still in flux. This period of emerging adulthood may be an important, yet overlooked, age for establishing long-term health behavior patterns. Several factors differentiate emerging adulthood from other life stages and have specific relevance to the formation of health behavior patterns, including identity development and shifting interpersonal influences. One defining characteristic of this life stage is the development of a self identity. Emerging adulthood is a time for the exploration of new ideologies and behaviors which allow individuals to express their individuality. Given previous research showing that identity (e.g., incorporating healthy lifestyle characteristics in the concept of one's self) is an important indicator of lasting health behavior change, emerging adulthood may be a particularly important time for establishing and intervening on long-term health behavior patterns (2,3). In addition, other psychosocial attributes associated with beneficial health behaviors (e.g., self-efficacy) develop or become established during this period of emerging adulthood (4), providing support for the unique importance of this life stage in long-term behavioral patterning. Emerging adulthood may also be a time for changing support systems and shifting interpersonal influences. Although the influence of parents and family is well established in the literature on childhood and, to a lesser extent, adolescent diet and physical activity patterns, little research has examined these issues among young adults. Young adults spend more leisure time alone compared to other age group (except retirees ≥55 years) (5) and are often assumed to be more disconnected from their family. However, some research suggests that closer relationships with parents (6,7) and siblings (8) may evolve as youth transition into college and adulthood (9,10). As youth become more independent, family and social network influences begin to shift and may serve different roles, as compared to that which they served in childhood and adolescence. Much additional research is needed to understand the evolving social influences in the emerging adult years and the extent to which this may influence health behavior patterns. Given the overall paucity of research in this area, more work is needed to understand better how the unique characteristics of emerging adulthood may contribute to establishing long-term behavioral patterns and the possible vulnerability of this life stage to various influences. The transition from adolescence to adulthood and the determinants of eating and physical activity is understudied. However, national trend data suggest that this is a risky period for the development of obesity, as well as unhealthy diet and physical activity practices. Weight gain. Research from national surveys and longitudinal cohorts has identified the transition between adolescence and adulthood as a period of increased risk for excess weight gain. Nationally representative cross-sectional survey data from the Behavioral Risk Factor Surveillance System indicated that from 1991 to 1998, the greatest magnitude of increase in obesity prevalence was among 18–29-year olds (increasing from 7.1 to 12.1%) (11). The prevalence of obesity among young adults more than doubled in the past 30 years. The most recent National Health and Nutrition Examination Survey (NHANES) data indicate that the prevalence has continued to increase since 1999 (ref. 12). Currently, 28.5% of 20–39-year olds are obese and 57.1% are overweight or obese (12). Nationally representative longitudinal cohort data from the National Longitudinal Study of Adolescent Health (Add Health) (13), assessing 9,795 adolescents (baseline age: 13–20 years in 1996), found that the 5-year incidence of obesity was nearly 13% (follow-up age: 19–26 years in 2001), whereas only 1.6% shifted from being obese to nonobese. In comparison to NHANES (1971–1974), the Add Health cohort showed substantial secular changes in the BMI distribution over time, particularly among individuals aged 19–26 years (13). In addition, findings from the CARDIA (Coronary Artery Risk Development in Young Adults) (14,15) longitudinal cohort illustrate both 5- and 10-year increases in weight among individuals 18–30 years of age at baseline (1985). Five-year weight gain was greater for men aged 18–24 years compared to men aged 25–30 years (14). Furthermore, the largest 10-year weight gains were seen among those in their early- to mid-twenties, as compared to those in their thirties (15). Physical activity. Although longitudinal data are limited, there is evidence of dramatic changes in lifestyle characteristics during this period. Cohort data from Add Health indicate that although most adolescents fail to meet national guidelines for physical activity (33.6%), even fewer meet these guidelines as young adults (12.7%) (16). In addition, findings from Project EAT (Eating Among Teens), a 5-year longitudinal cohort study of Minnesota adolescents, confirm such adverse changes in activity patterns during the transition from high school to young adulthood (17). Findings showed longitudinal changes in moderate to vigorous physical activity, particularly among girls (decreasing from 5.1 to 3.5 h/week aged from 16 to 20 years), and leisure time computer use, particularly among boys (increasing from 10.4 to 14.2 h/week aged from 16 to 20 years). Overall, many changes in physical activity patterns began during the transition from junior to senior high school and continued during the transition from high school to post-high school. One notable exception is moderate to vigorous physical activity among boys, which only began to decline during the transition after high school. Furthermore, a recent analysis of the National Health Interview survey data (18) indicated that age-related declines in physical activity are particularly pronounced between 15 and 18 years of age and continue through age 21. Physical activity has been shown to decline even further with specific life events typically following emerging adulthood (such as moving into a live-in relationship, getting married, and becoming a parent), but generally do not appear to continue to decline with age after mid-adulthood (30–64 years) (18). Thus health-promotion efforts to increase activity during emerging adulthood may be particularly important. Dietary intake. Research also suggests that declines in overall-diet quality may accompany these unfavorable shifts in activity patterns during the transition to adulthood (19,20). For example, fast food consumption has been associated with weight gain over time, and findings from national survey data indicate that fast food restaurant use is highest in young adulthood: 52% of 20–39 years reported eating fast food on one or both days of the Continuing Survey of Food Intakes by Individuals (1994–1996, 1998) (21). These data also indicate that soft drink intake is highest among 19–39-year olds compared to other age groups (22). In addition, NHANES data illustrate that a majority of young adults (aged 20–29 years) consume <1 serving/day of fruit (males 63%, females 59%) and vegetables (including potatoes, males 19%, females 20%) (23). Unfortunately, however, the collapsing of ages 19–39 years does not allow for an examination of the emerging adult period. Longitudinal findings from Project EAT also indicate adverse changes in dietary intake. For example, total fruit and vegetable intake decreased significantly (by >½ serving/day) during the 5-year transition period after high school (24). Add Health data indicate that fast food consumption markedly increased and consumption of breakfast decreased across a 5-year transition between adolescence and adulthood (25). The Bogalusa Heart Study (19), a longitudinal study of a biracial cohort following children >15 years into young adulthood, also showed a substantial decline in diet quality as individuals progressed through this transition. Findings indicate that individuals consumed less fruits/fruit juice and milk (19) and more sweetened beverages, salty snacks, and beef as young adults (19–28 years) than as children. Several studies have reported that despite changes in diet quality, there is substantial tracking in dietary intake between adolescence and young adulthood, as well as into later adulthood (20,26,27). Weight status also shows a high degree of tracking over time (28). Thus setting a “trajectory” for beneficial health behavior patterns and dietary intake during this time may be an important step toward initiating lasting healthy behaviors. Furthermore, a growing number of individuals are now becoming obese during adolescence and are exposed to a wide array of precursors to poor-diet quality and inactivity before the emerging adult years. For example, secular trends suggest declining rates of family meals and home food preparation (29), potentially leaving young adults without the skills to prepare foods and plan healthful meals on their own. Thus, challenges lie in reversing the effects of adverse adolescent exposures during the emerging adult years and promoting healthful long-term behavior patterns in all segments of the population. Dietary intake is influenced by a variety of factors, including individual, interpersonal, institutional, and macro-system influences. Although many of these influences are thought to be shared by a wide range of age groups, food and beverage marketing may be a particularly potent macro-level influence for emerging adults. The food, beverage and restaurant industries are estimated to have spent >$11 billion on advertising in 2004 alone (30). Young adults aged 18–24 years are a highly desirable market, particularly among fast food and soft drink companies. Marketing campaigns geared toward young adults, particularly males, have brought increased sales to fast food restaurant chains in the past decade (31,32,33,34). These campaigns have been specifically designed to increase product recognition, sales and brand loyalty among this group and have been widely promoted in young adult media markets. A number of these successful campaigns have targeted issues such as fast food late night dining and value pricing (32,35). For example, in launching its late night “Fourthmeal” campaign (with “Fourthmeal” marketed as “the meal between dinner and breakfast”), Taco Bell cites industry research in its press release indicating that nearly 50% of males aged 18–29 years are eating out after 7 pm (32). Industry research also suggests that young males spend well above market averages in these visits, averaging over $7.00 (ref. 36). To our knowledge, similar peer-reviewed evidence in the scientific literature is not available to confirm these trends. A number of these successful industry-driven campaigns have received recognition from the marketing and advertising community, for example, receiving EFFIE Awards (prestigious annual advertising awards) for their work in effectively targeting young adults. Honored campaigns include: • Hardee's. In 2001, industry research found that among its target markets Hardee's was “the most avoided restaurant in the fast food category” (31). Launching a major initiative targeting frequent fast food consumers, the company conducted “a segmentation analysis … to create a landscape from which we selected a more meaningful target for Hardee's. We called this target ‘Young Hungry Guys.’ This group is defined as young burger eaters (men 16–34) who want a more adult-like place to eat the burgers they love. This group seeks out big burgers as their food of choice, has the most growth potential for Hardee's and represent the heaviest usage in the fast food category” (31). With this, the Thickburger was introduced (providing ∼850–1,400 calories/burger). As a result, the company grew from the lowest to the highest ranked leading quick-service restaurant among young male fast food consumers (31). • Burger King. In February 2004 after significantly declining sales, Burger King refocused its efforts on its heaviest users, identified as males aged 16–34 years (34). To do so, they introduced the large-sized Angus Steak Burger. Describing its creative strategy, the marketing team states that “since the beginning of time, men have been eating large amounts of meat cooked over fires. For thousands of years, society has been wired to associate this kind of indulgence with power, pleasure and status. The problem is our culture is on an anti-indulgence craze the likes of which we have never seen before. Our strategy was to give our target permission to indulge in a great tasting burger and not apologize for it. And nothing gives them permission better than the affordable, deeply satisfying fire-grilled Angus Steak Burger…” (34). After increasing its market share among young men, this single-menu item subsequently accounted for 10% of sales dollars for Burger King. • Jack in the Box. 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