such as sodium. Portion size can be affected by packaging sizes in processed food, portion sizes served in restaurant/foodservice operations, and the behavior of individual consumers.

As shown in Figure 2-5, the portion sizes of sample foods generally increased between 1977 and 1996 (Nielsen and Popkin, 2003). In general, this same pattern of increasing portion size over time was seen for the same foods when consumed at home or at a restaurant or when obtained from fast food vendors—suggesting that increasing portion size is a phenomenon common to all food channels.

Moreover, increasing portion sizes are not limited to the sample foods in Figure 2-5. Smiciklas-Wright et al. (2003) found that increasing portion sizes are widespread across a number of food categories. Using the Continuing Survey of Food Intakes by Individuals (CSFII) from 1989–1991 and 1994–1996, they found that nearly one-third of the servings from 107 food categories exhibited this pattern. Clearly, larger portion sizes will deliver greater amounts of sodium if sodium densities are not reduced.

With limited data on portion sizes across food channels, another way of estimating relative changes in sources of nutrients is to look at changing patterns in sources of energy intake. As shown in Figure 2-6, overall energy intake increased between 1977 and 1996 (Nielsen and Popkin, 2003). This overall increase was associated with a decreasing intake from at-home foods and an increasing intake from foods consumed away from home. These data suggest that even though sodium densities were similar for foods defined as eaten “at home” and “away from home” (see Figure 2-4,

FIGURE 2-5 Differences in portion sizes 1977–1978 to 1994–1996 for key food items consumed by persons 2 or more years of age.

SOURCE: Nielsen and Popkin, 2003. Journal of the American Medical Association 289(4), pp. 450–453. Copyright © 2003 American Medical Association. All rights reserved.