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The Rising Cost of Low-Energy-Density Foods

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Abstract

Background

Consuming lower-energy-density foods is one recommended strategy for management of body weight. This cross-sectional study used retail food prices to test the hypothesis that low-energy-density foods are not only more costly per kilocalorie, but have increased disproportionately in price as compared to high-energy-density foods.

Design

For a list of 372 foods and beverages belonging to a food frequency questionnaire database, retail prices were obtained from major supermarket chains in the Seattle, WA, metropolitan area in 2004 and 2006. Energy density of all items was calculated and prices were expressed as $/100 g edible portion and as $/1,000 kcal. Foods were stratified by quintiles of energy density and the differences in energy cost and in percent price change were tested using analyses of variance.

Results

High-energy-density foods provided the most dietary energy at least cost. Energy cost of foods in the bottom quintile of energy density, beverages excluded, was $18.16/1,000 kcal as compared to only $1.76/1,000 kcal for foods in the top quintile. The 2-year price change for the least energy-dense foods was +19.5%, whereas the price change for the most energy-dense foods was −1.8%.

Conclusion

The finding that energy-dense foods are not only the least expensive, but also most resistant to inflation, may help explain why the highest rates of obesity continue to be observed among groups of limited economic means. The sharp price increase for the low-energy-density foods suggests that economic factors may pose a barrier to the adoption of more healthful diets and so limit the impact of dietary guidance.

Section snippets

Methods

The present study used a market-basket approach to assess the prices of foods. A market basket is simply a list of defined products in purchasable form. The same approach is used by the US Bureau of Labor Statistics in monitoring prices and inflation in goods and services as part of the Consumer Price Index. Previous research studies have used the market-basket method to assess the price and availability of food in different geographical areas (17).

Results

Food-price collection methods were highly reliable in the 2 years of the present study. Figure 1 illustrates the relationship between food prices collected ($/100 g) in 2004 and in 2006 for the same 372 foods. There was a strong correlation between 2004 and 2006 prices (r2=0.95), and the average price increase calculated for all foods and beverages was 7.9%.

Discussion

Improving the nutrients-to-energy ratio in the American diet is the stated goal of the 2005 Dietary Guidelines for Americans and the 2005 US Department of Agriculture’s MyPyramid (22, 23). Many studies have provided ample evidence to justify the adoption of lower-energy-density but high-quality diets (6, 7), whether for the purpose of weight management (8) or the prevention of chronic disease (24, 25). Few of those studies have addressed the issue of food prices and diet costs (16).

Being able

Limitations of the Present Study

The present analyses were based on prices collected from only three major supermarket chains in a single, major US metropolitan area, and thus cannot account for geographic variation in prices or in inflationary trends (33). In addition, each food and beverage was priced using methods that did not take into account sale prices, loyalty-card discounts, coupons, or other shopping strategies that can help consumers control food expenditures (34). Moreover, the particular group of foods or “market

Conclusions

The sharp price increase observed for vegetables and fruit relative to fats and sweets suggests that the ability to adopt more-healthful diets may be limited by economic constraints. Although low-energy-density foods are undoubtedly associated with better health outcomes, they are also more costly (9, 36) and tend to be purchased by the more-affluent consumer (37). The energy density of the American diet is reported to have risen (38), suggesting that the consumer is seeking out lower-cost

P. Monsivais is a research fellow in the Nutritional Sciences Program, School of Public Health and Community Medicine and the Department of Dental Public Health Sciences, School of Dentistry, University of Washington, Seattle.

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    P. Monsivais is a research fellow in the Nutritional Sciences Program, School of Public Health and Community Medicine and the Department of Dental Public Health Sciences, School of Dentistry, University of Washington, Seattle.

    A. Drewnowski is professor and director, Nutritional Sciences Program, School of Public Health and Community Medicine, University of Washington, Seattle.

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