Weight Gain During Pregnancy: Reexamining the Guidelines (2009)

As the prevalence of obesity rises among childbearing-aged women and women entering pregnancy, important shifts in diet and physical activity have also occurred. In a recent study, Nielsen and colleagues (2002) used nationally representative data from the 1977-1978 Nationwide Food Consumption Survey and the 1989-1991 and 1994-1996 Continuing Surveys of Food Intake by Individuals to investigate the trends in total energy intake and energy intake by meal pattern type (Figure B-1). Data were stratified by age but not sex. These investigators found that among U.S. adults aged 19-39 years, there was an 18 percent increase in total energy intake over the 20-year period (1856 to 2198 kcal/d). When separated into energy from meal pattern type, the major contributor to this overall increase in energy intake was a sharp 58 percent increase in energy from snacks (244-387 kcal/d). Additionally, the percent of total energy from key food groups, such as salty snacks, sweetened beverages, candy, pizza, French fries, cheeseburgers, and Mexican-style food, increased between survey years 1977-1978 and 1994-1996.

These authors further investigated trends in beverage intake using the aforementioned data sources plus the 1999-2001 nationally-representative NHANES. For all age groups, including adults aged 19 to 39 years, sweet-

FIGURE B-1 Trends in energy intake and meal pattern type, U.S. adults aged 19-39 years.

SOURCE: Nielsen et al., 2002.

ened beverage intake increased and milk consumption decreased between survey years 1977-1978 and 1999-2001 (Figure B-2) (Nielsen and Popkin, 2004). Specifically, energy from soft drinks nearly tripled (2.8 to 7.0 percent [approximately 50 to 144 kcal per person per day]), energy from fruit drinks doubled (1.1 to 2.2 percent [from 20 to 45 kcal per person per day]), and energy from milk decreased (8.0 to 5.0 percent [from 143 to 99 kcal per person per day]).

Taken together, these findings illustrate an increase in consumption of foods of low nutrient density in the general population. This has special implications for pregnancy and lactation, which require modest increases in energy intake but proportionally greater increases in vitamin and mineral intake.

The U.S. Dietary Guidelines represent federal nutrition policy. The recommendations of the Dietary Guidelines are interpreted for use by healthy Americans over 2 years of age in MyPyramid (available online: http://www.MyPyramid.gov [accessed October 16, 2008]). The current MyPyramid recommends that females aged 14-18 years and 31-50 years consume 8 combined servings of fruits and vegetables, while 9 combined servings is recommended for females aged 19-30 years. MyPyramid also makes more specific recommendations about types of vegetables, including dark green and orange vegetables, and legumes to ensure consumption of the variety of nutrients available from these foods. When the Guenther et al. (2006) exam-

FIGURE B-2 Trends in U.S. beverage consumption 1977-2001: percent of total energy intake.

SOURCE: Nielsen and Popkin, 2004.

ined sub-groups of vegetables, mean intakes for childbearing-aged women were below the recommended amounts for all subgroups except for starchy vegetables (Figure B-3). These data clearly illustrate that childbearing-aged women failed to meet recommendations for fruits and vegetables.

Another method of quantifying the overall quality of American’s diets is through the use of the Healthy Eating Index-2005 (HEI-2005), a tool designed to measure compliance of diets with the key, diet-related recommendations of the 2005 Dietary Guidelines for Americans (HHS/USDA, 2005). The HEI-2005 has 12 components, as seen in Table B-5 (Guenther et al., 2006). For most components, higher intakes result in higher scores. Note, however, that for three components, saturated fat, sodium, and calories from solid fats, alcoholic beverages, and added sugars (SoFAAS), lower intake levels result in higher scores because lower intakes are more desirable. Monitoring changes in the HEI-2005 scores can provide a method for nutrition surveillance in the population.

In a recent analysis, trends in the HEI-2005 scores and its components were published for all Americans two years of age and older (subgroups of the population were not studied). From 1994-1996 to 2001-2002, there was little change in either overall HEI-2005 score or its components. The average HEI-2005 score was 58.2 out of 100 possible points in both time periods. American’s diets consistently met recommendations for the groups “Total Grains” and “Meat and Beans,” but were far below the maximum

FIGURE B-3 Mean daily intakes of vegetables by subtype among U.S. females 19-30 years of age.

SOURCE: Guenther et al., 2006.

score for the groups, “Dark Green and Orange Vegetables” and “Legumes” as well as whole grains. Intakes from SoFAAS were well below the recommendations, as reflected in low scores on these components. From 1994-1996 to 2001-2002 the HEI-2005 score declined for the groups “Whole Fruit,” “Total Vegetables,” and “Whole Grains” while the score for the groups “Milk,” “Oils,” and “Sodium” improved.

Some of these dietary pattern changes may be a result of the trend toward obtaining a greater proportion of food outside the home. Self-reported dietary data from national surveys was used to show that the percentage of total energy intake obtained from foods consumed at home decreased from 77 in 1977-1978 to 65 percent from 1994-1996 (Figure B-4) (Nielsen et al., 2002). The amount of energy obtained from foods consumed from restaurants, including fast food establishments, doubled from 9 to 21 percent during this same period.

The aforementioned analysis relied on dietary intake data obtained from surveys. There is no “gold standard” method of assessing dietary intakes in individuals, and all self-reported dietary intake data have inherent biases. Therefore food supply data, collected directly from food producers and distributors, are often used to examine trends in American dietary patterns. The estimates are adjusted for spoilage, cooking losses, plate waste, and other food losses accumulated throughout the marketing system and

FIGURE B-4 Trends in energy intake (percent energy) by location, Americans aged 2+ years.

SOURCE: Nielsen et al., 2002.

the home. Analysis of trends in food supply data provide the same conclusions regarding trends in increasing energy intake and overall diet quality of Americans as self-reported survey data.

The most recent loss-adjusted annual per capita food supply data analyses by the USDA’s Economic Research Service suggests a 12 percent increase in total energy intake (~300 kcal per person per day) from 1985 to 2000 (USDA, 2002; available online: http://www.ers.usda.gov/publications/FoodReview/DEC2002/frvol25i3a.pdf [accessed April 16, 2009]) (Figure B-5). Of the 300-kcal increase, grains (mainly refined grains) accounted for 46 percent; added fats, 24 percent; added sugars, 23 percent; fruits and vegetables, 8 percent of the increase. At the same time, energy intake from the meat and dairy groups together declined by 1 percent. When the per capita food supply data in 2000 was compared with the 1992 Food Guide Pyramid recommendations as a marker of overall diet quality, intakes exceeded recommendations for grains, meats, added fats, and added sugars, and fell below recommendations for dairy, fruits, and non-starchy vegetables (USDA, 2002; available online: http://www.ers.usda.gov/publications/FoodReview/DEC2002/frvol25i3a.pdf [accessed April 16, 2009]).

FIGURE B-5 Energy from the U.S. per capita food supply (adjusted for losses).

¹Rounded to the nearest hundred.

²Not calculated for years beyond 1970.

SOURCE: USDA, 2002; available online at http://www.ers.usda.gov/publications/FoodReview/DEC2002/frvol25i3a.pdf [accessed April 16, 2009].

Guenther P. M., K. W. Dodd, J. Reedy and S. M. Krebs-Smith. 2006. Most Americans eat much less than recommended amounts of fruits and vegetables. Journal of the American Dietetic Association 106(9): 1371-1379.

HHS/USDA (U.S. Department of Health and Human Services/United States Department of Agriculture). 2005. Dietary Guidelines for Americans, 2005. 6th Edition. Washington, DC: Government Printing Office.

IOM (Institute of Medicine). 2006. Dietary Reference Intakes: The Essential Guide to Nutrient Requirement. Washington, DC: The National Academies Press.

Nielsen S. J. and B. M. Popkin. 2004. Changes in beverage intake between 1977 and 2001. American Journal of Preventive Medicine 27(3): 205-210.

Nielsen S. J., A. M. Siega-Riz and B. M. Popkin. 2002. Trends in energy intake in U.S. between 1977 and 1996: similar shifts seen across age groups. Obesity Research 10(5): 370-378.

Websites:

http://www.MyPyramid.gov

http://www.cnpp.usda.gov/Publications/NutritionInsights/Insight37.pdf

http://www.ers.usda.gov/publications/FoodReview/DEC2002/frvol25i3a.pdf