The interrelated areas of family life, ethnic diversity, eating patterns, physical activity, and media use—discussed below—are all aspects of societal change that must be considered. Singly and in concert, the trends in these areas will strongly influence prospects for preventive and corrective measures.
The changing context of American families includes several distinct trends such as the shifting role of women in society, delayed marriage, childbearing outside of marriage, higher divorce rates, single parenthood, and work patterns of parents (NRC, 2003). Among the many important transformations that have occurred are expanded job opportunities for women, which have led to more women entering the workforce. Economic necessities have also prompted this trend. Moreover, married mothers are increasingly more likely than they were in the past to remain in the labor force throughout their childbearing years.
Women's participation in the labor force increased from 36 percent in 1960 to 58 percent in 2000 (Luckett Clark and Weismantle, 2003). Since 1975, the labor force participation rate of mothers with children under age 18 has grown from 47 to 72 percent, with the largest increase among mothers with children under 3 years of age (U.S. Department of Labor, 2004). Over the same period, men's labor force participation rates declined slightly from 78 percent to 74 percent (Population Reference Bureau, 2004b). In 2002, only 7 percent of all U.S. households consisted of married couples with children in which only the husband worked.
These trends, together with lower fertility rates, a decrease in average household size, and the shift in household demographics from primarily married couples with children to single person households and households without children, have caused the number of meal preparers in U.S. households who cook for three or more people to decline (Population Reference Bureau, 2003; Sloan, 2003).
It has been suggested that smaller households experience fewer economies of scale in home preparation of meals than do larger families. Preparing food at home involves a set amount of time for every meal that changes minimally with the number of persons served. Eating meals out involves the same marginal costs per person. Moreover, changes in salary and the lower prices of prepared foods may have reduced the value of time previously used to prepare at-home meals. Thus, incentives have been shifted away from home production toward eating more meals away from home (Sturm, 2004). Time-use trends for meal preparation at home reveal a gradual decline from 1965 to 1985 (44 minutes per day versus 39 minutes per day) and a steeper decline from 1985 to 1999 (39 minutes per day versus 32 minutes per day) (Robinson and Godbey, 1999; Sturm, 2004).
The racial and ethnic composition of children in the United States is becoming more diverse. In 2000, 64 percent of U.S. children were white non-Hispanic, 15 percent were black non-Hispanic, 4 percent were Asian/ Pacific Islander, and 1 percent were American Indian/Alaska Native. The proportion of children of Hispanic origin has increased more rapidly than the other racial and ethnic groups from 9 percent of the child population in
1980 to 16 percent in 2000 (Federal Interagency Forum on Child and Family Statistics, 2003).
Differences among ethnic groups (e.g., African American, American Indian, Hispanic, and Asian/Pacific Islanders) include variations in household composition and size—particularly larger household size in Hispanic and Asian populations (Frey, 2003)—and in other aspects of family life such as media use and exposure, consumer behavior, eating, and physical activity patterns (Tharp, 2001; Nesbitt et al., 2004).
Ethnic minorities are projected to comprise 40.2 percent of the U.S. population by 2020 (U.S. Census Bureau, 2001), and the food preferences of ethnic families are expected to have a significant impact on consumers' food preferences and eating patterns (Sloan, 2003). The higher-than-aver-age prevalence of obesity in several ethnic minority populations may indicate differences in susceptibility to unfavorable lifestyle trends and the consequent need for specially designed preventive and corrective strategies (Kumanyika, 2002; Nesbitt et al., 2004).
As economic demands and the rapid pace of daily life increasingly constrain people's time, food trends have been marked by convenience, shelf stability, portability, and greater accessibility of foods throughout the entire day (Food Marketing Institute, 1996, 2003; French et al., 2001; Sloan, 2003). Food has become more available wherever people spend time. Because of technological advances, it is often possible to acquire a variety of highly palatable foods, in larger portion sizes, and at relatively low cost. Research has revealed a progressive increase, from 1977 to 1998, in the portion sizes of many types of foods and beverages available to Americans (Nielsen and Popkin, 2003; Smiciklas-Wright et al., 2003); and the concurrent rise in obesity prevalence has been noted (Nestle, 2003; Rolls, 2003).
Foods eaten outside the home are becoming more important in determining the nutritional quality of Americans' diets, especially for children (Lin et al., 1999b; French et al., 2001). Consumption of away-from-home foods comprised 20 percent of children's total calorie intake in 1977-1978 and rose to 32 percent in 1994-1996 (Lin et al., 1999b). In 1970, household income spent on away-from-home foods accounted for 25 percent of total food spending; by 1999, it had reached nearly one-half (47 percent) of total food expenditures (Clauson, 1999; Kennedy et al., 1999).
The trend toward eating more meals in restaurants and fast food establishments may be influenced not only by simple convenience but also in response to needs such as stress management, relief of fatigue, lack of time, and entertainment. According to a 1998 survey conducted by the National Restaurant Association, two-thirds of Americans indicated that patronizing a restaurant with family or friends allowed them to socialize and was a better use of their leisure time than cooking at home and cleaning up afterward (Panitz, 1999).
For food consumed at home, never has so much been so readily available to so many—that is, to virtually everyone in the household—at low cost and in ready-to-eat or ready-to-heat form (French et al., 2001; Sloan, 2003). Increased time demands on parents, especially working mothers, have shifted priorities from parental meal preparation toward greater convenience (French et al., 2001), and the effects of time pressures are seen in working mothers' reduced participation in meal planning, shopping, and food preparation (Crepinsek and Burstein, 2004). Industry has endeavored to meet this demand through such innovations as improved packaging and longer shelf stability, along with complementary technologies, such as microwaves, that have shortened meal preparation times.
Another aspect of this trend toward convenience is an increased prevalence, across all age groups of children and youth, of frequent snacking and of deriving a large proportion of one's total daily calories from energy-dense snacks (Jahns et al., 2001). At the same time, there has been a documented decline in breakfast consumption among both boys and girls, generally among adolescents (Siega-Riz et al., 1998) and in urban elementary school-age children as compared to their rural and suburban counterparts (Gross et al., 2004); further, children of working mothers are more likely to skip meals (Crepinsek and Burstein, 2004).
There are also indications that children and adolescents are not meeting the minimum recommended servings of five fruits and vegetables daily recommended by the Food Guide Pyramid (Cavadini et al., 2000; American Dietetic Association, 2004). This trend is partially explained by the limited variety of fruits and vegetables consumed by Americans. In 2000, five vegetables—iceberg lettuce, frozen potatoes, fresh potatoes, potato chips, and canned tomatoes—accounted for 48 percent of total vegetable servings and six fruits (out of more than 60 fruit products)—orange juice, bananas, apple juice, apples, fresh grapes, and watermelon—accounted for 50 percent of all fruit servings (Putnam et al., 2002).
These trends have contributed to an increased availability and consumption of energy-dense foods and beverages. As summarized in Table 1-1 and Figures 1-1 through 1-3, trends in the dietary intake of the general U.S. population parallel trends in the dietary intake of children and youth. A more in-depth discussion of caloric intake, energy balance, energy density, Dietary Guidelines for Americans, and the Food Guide Pyramid is included in Chapters 3, 5, and 7.
Physical activity is often classified into different types including recreational or leisure time, utilitarian, household, and occupational. The direct surveillance of physical activity trends in U.S. adults began only in the 1980s and was limited to characterizing leisure-time physical activity. In 2001, CDC began collecting data on the overall frequency and duration of time spent in household, transportation, and leisure-time activity of both moderate and vigorous intensity in a usual week through the state-based Behavioral Risk Factor Surveillance System (BRFSS) (CDC, 2003c).
National surveys conducted over the past several decades suggest an increase in population-wide physical activity levels among American men, women, and older adolescents; however, a large proportion of these populations still do not meet the federal guidelines for recommended levels of total daily physical activity.3 The data for children's and youth's leisure time and physical activity levels reveal a different picture than the adult physical activity trend data that are summarized in Table 1-2.
Trend data collected by the Americans' Use of Time Study, through time-use diaries, indicated that adults' free time increased by 14 percent between 1965 and 1985 from 35 hours to an average total of nearly 40 hours per week (Robinson and Godbey, 1999). Data from other population-based surveys, including the National Health Interview Survey, National Health and Nutrition Examination Survey (NHANES), BRFSS, and the Family Interaction, Social Capital and Trends in Time Use Data (19981999), together with trend data on sports and recreational participation, suggest minor to significant increases in reported leisure-time physical activity among adults (Pratt et al., 1999; French et al., 2001; Sturm, 2004).
Data from the 1990-1998 BRFSS4 revealed only a slight increase in self-reported physical activity levels among adults (from 24.3 percent in 1990 to 25.4 percent in 1998), and a decrease in respondents reporting no physical activity at all (from 30.7 percent in 1990 to 28.7 percent in 1998) (CDC, 2001).
Women, older adults, and ethnic minority populations have been identified as having the greatest prevalence of leisure-time physical inactivity (CDC, 2004b). In general, the prevalence of self-reported, no leisure-time physical activity was highest in 1989, and declined to its lowest level in 15 years among all groups in 35 states and the District of Columbia based on
3The Surgeon General's report on physical activity and health suggests that significant health benefits can be obtained by Americans who include a moderate amount of physical activity (e.g., 30 minutes of brisk walking) on most if not all days of the week (DHHS, 1996).
4The BRFSS is a population-based, randomly selected, self-reported telephone survey conducted among the noninstitutionalized U.S. adult population aged 18 years and older throughout the 50 states (CDC, 2003c).
TABLE 1-1 Trends in Food Availability and Dietary Intake of the U.S. Population and of U.S. Children and Youtha
Dietary Intake Trend
U.S. Children and Youth
Portion sizes of foods
Total energy intake derived from away-from-home sources
Total energy intake
Portion sizes of most foods consumed by adults both at home and away from home (except pizza) increased between 1977 and 1996 (Nielsen and Popkin, 2003).
Total energy intake increased from 18% to 34% for adults between 1977-1978 and 1995 (Lin et al., 1999a).
Between 1971 and 2000, average energy intake increased from 2,450 to 2,618 calories for men and 1,542 to 1,877 kcal for women (CDC, 2004a).
Between 1989 andl991 and 1994-1996, total energy increased 8.6% and 9.5%, according to food supply and CSFII data, respectively (Chanmugam et al., 2003).
Between 1983 and 2000, calories per capita increased by 20% (USDA, 2003) (Figure 1-1).
Between 1971 and 2000, the percentage of calories from total fat decreased for men (from 36.9%to 32.8%) and women (from 36.1% to 32.8%) (CDC, 2004a). However, the intake of grams of total fat increased among women and decreased among men (CDC, 2004a) (Figure 1-2).
Portion sizes for children aged 2 years and older increased for most foods consumed both at home and away from home between 1977 and 1996 (Nielsen and Popkin, 2003).
Total energy intake increased from 20% to 32% for children between 1977-1978 and 1994-1996 (Lin et al., 1999b).
No significant increased trends in energy intake were observed in children aged 6-11 years between 1977-1978 and 1994-1996, 1998 (Enns et al., 2002).
Total calories consumed by adolescent boys aged 12 to 19 years increased by 243 between 1977-1978 and 1994-1996 from 2,523 to 2,766 calories (Enns et al., 2003). Total calories consumed by adolescent girls aged 12 to 19 years increased by 123 between 1977-1978 and 1994-1996 from 1,787 to 1,910 calories (Enns et al., 2003).
Between 1965 and 1996, the proportion of energy from total fat consumed by children decreased from 39% to 32%, and saturated fat from 15% to 12% (Cavadini et al., 2000).
Children aged 6 to 11 years in 1994-1996, 1998 consumed 25% of calories from discretionary fat (USDA, 2000; Enns et al., 2002).
Added dietary sweeteners Between 1977 and 2000, an 83 calorie/day increase in caloric sweeteners was observed in the U.S. for all individuals 2 years and older, representing a 22% increase in the proportion of energy derived from caloric sweeteners (Popkin and Nielsen, 2003).
Between 1982 and 1997, per capita consumption of sweeteners increased 28% (34 pounds) (Putnam and Gerrior, 1999).
Dairy and milk consumption Between 1970 and 1997, the consumption of milk per capita decreased from 31 gallons to 24 gallons, while cheese consumption increased 146% from 11 pounds/person in 1970 to 28 pounds/person in 1997 (French et al., 2001).
Americans consumed 2.5 times as much cheese and drank 23% less milk per capita in 1997 than in 1970 (Putnam and Gerrior, 1999).
For adolescents aged 12 to 19 years, girls consumed 25% and boys consumed 26% of their calories from added fat (USDA, 2000; Enns et al., 2003).
Children aged 6 to 11 years in 1994 to 1996 and 1998 consumed 21-23 teaspoons of added sugars in a 1,800-2,000 calorie diet which exceeded the Food Guide Pyramid recommendation of 6-12 teaspoons for a 1,600-2,200 calorie diet (USDA, 1996; Enns et al., 2002).
Milk consumption decreased by 37% in adolescent boys and 30% in adolescent girls between 1977-1978 and 1994 (Cavadini et al., 2000).
In 1977-1978, children aged 6 to 11 years consumed four times as much milk as any other beverage, and adolescents aged 12 to 19 years drank 1.5 times as much milk as any other beverage. In 1994-1996 and 1998, children aged 6 to 11 consumed 1.5 times as much milk as soft drinks, and by 1994-1996 adolescents consumed twice as much soft drinks as milk (French et al., 2001).
TABLE 1-1 Continued
Dietary Intake Trend
Fruit and vegetable consumption
In 1997, Americans consumed 24% more fruit and vegetables per capita than they did in 1970 (French et al., 2001).
Meat, poultry, and fish consumption
Total meat consumption per capita increased by 19 lbs from 1970 to 2000. In 2000, individual Americans consumed 16 pounds less red meat than in 1970, 32 lbs more poultry, and 3 lbs more fish and shellfish (Putnam et al., 2002).
U.S. Children and Youth
Adolescent intake of whole milk decreased while cheese increased. In 1994-1996, for adolescents aged 12 to 19 years, only 12% of girls and 30% of boys consumed the number of dairy servings recommended by the Food Guide Pyramid (USDA, 2000; Enns et al., 2002, 2003).
In 1977-1978 children aged 6 to 11 years consumed more total vegetables than children in 1994-1996, 1998 (Enns et al., 2002). In 1994-1996, 1998, only 24% of girls and 23% of boys consumed the number of Food Guide Pyramid recommended fruit servings (USDA, 2000; Enns et al., 2002).
In 1994-1996 adolescents aged 12 to 19 years, only 18% of girls and 14% of boys consumed the number of Food Guide Pyramid recommended fruit servings (USDA, 2000; Enns et al., 2003).
In 1994-1996 and 1998 the percentages of children aged 6 to 11 years and adolescents aged 12 to 19 years consuming meat, poultry, fish, and eggs were lower than in 1977-1978 (USDA, 2000; Enns et al., 2002, 2003).
Annual soft drink consumption increased from 34.7 to 44.4 gallons per capita between 1987-1991 and 1997 (French et al., 2001).
Portion sizes of soft drinks increased by 49 calories (from 13.1 to 19.9 fl oz) between 1977 and 1996 (Nielsen and Popkin, 2003).
Soft drink consumption nearly tripled among adolescent boys from 7 to 22 ounces per day between 1977-1978 and 1994 (Guthrie and Morton, 2000; French et al., 2003).
By 14 years of age, 32% of adolescent girls and 52% of adolescent boys consume three or more 8-ounce servings of soda daily (Gleason and Suitor, 2001).
Children as young as 7 months old are consuming soda (Fox et al., 2004).
NOTE: CSFII = Continuing Survey of Food Intakes by Individuals.
aFood availability (per capita intake) is based on food supply data; dietary intake trends are based on measured or self-reported food consumption data.
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FIGURE 1-1 U.S. macronutrient food supply trends for carbohydrates, protein,
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FIGURE 1-1 U.S. macronutrient food supply trends for carbohydrates, protein, and total fat, 1970-2000.
SOURCES: Putnam et al., 2002; USDA, 2003.
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