The portion sizes of commonly consumed foods appear to have increased in size during the past 20 years (1). Larger food portions provide more energy (kcal) than smaller portions and could be contributing to the increased prevalence of overweight and obesity since the 1970s (2-4). The 2001 Surgeon General's Call to Action on obesity prevention stressed the need to address portion size as a factor in weight control, raise consumer awareness of reasonable portion sizes, and encourage food companies to provide reasonably sized portions (5). Because larger portions have become typical, consumers have increasing difficulty recognizing amounts of food that are appropriate for their weight and activity levels (6,7). Although the Call to Action advised consumers to "choose sensible portions," it did not define the sizes of such portions (8).
Nutritionists use two sets of standard serving sizes when counseling clients about healthful eating and weight-loss strategies: one developed by the US Department of Agriculture (USDA) for dietary guidance and the other by the Food and Drug Administration (FDA) for food labeling. Both define serving sizes of specific weight and volume and, therefore, energy and nutrient content. The USDA's Food Guide Pyramid, for example, lists the sizes of standard grain servings as follows: 1 slice bread, 1/2 cup cooked pasta, 1/2 bagel, or 1 oz ready-to-eat cereal (9). In defining standard servings, the USDA considered nutrient content, ease of use, tradition, and typical intake based on median amounts reported in the 1977-1978 Nationwide Food Consumption Survey (NFCS) (10-12). When the 2000 edition of the Dietary Guidelines advises choosing "sensible portions "it refers to Pyramid serving definitions (13). The FDA defines somewhat different serving sizes for Nutrition Facts labels. These were intended to represent amounts of foods commonly consumed based on data from dietary intake surveys: the National Food Consumption Surveys of 1977-1978 and 1987-1988 and the 1985-1986 Continuing Survey of Food Intake of Individuals (CSFII) (14,15). Because the surveys were conducted 15 to 25 years ago, standard servings may be smaller than marketplace portions (16). If so, nutritionists need to be able to compare serving size standards with the sizes of foods purchased ("marketplace portions") and, presumably, consumed; nearly half of all food expenditures are for items prepared and served outside the home (17). However, because so little is known about the sizes of marketplace portions, we measured them directly and compared them with USDA and FDA standards. We also investigated trends in portion sizes to determine whether they correlate to rising rates of obesity.
We examined the sizes of ready-to-eat foods from take-out places, fast-food outlets, and family-type restaurants; these account for much of the recent increase in out-of-home food consumption, rank highest in sales, and exhibit the highest sales growth (18-20). We sampled foods from categories reported in national surveys as major contributors of energy in US diets and marketed as single portions: white bread products, cakes, alcoholic beverages, hamburgers, steak, soda, french fries, pasta, and pizza (21,22). We obtained size information from package labels or from manufacturers. When such information was unavailable, and to confirm the accuracy of label weights and manufacturers' information, we weighed at least two samples of each food item from the same location using a calibrated Sysco Digital Portion Scale (Model SDS-l0; Sysco Foodservice, Houston, TX) and recorded average weights. A pilot project demonstrated that this method would be effective (23). We sampled foods from at least four of each type of venue (eg, four fast-food chains), totaling 32 establishments. Details about the weighing method and its validation are described …