Overly Ample Food Portions Beguile College Students' Eyes

NEW BRUNSWICK, N.J., Sept. 1 -- Portions of buffet-style food that college students pile on their trays have generally grown significantly in 20 years.

Because overly ample portion sizes are so common, many younger Americans may have lost their perspective on what an appropriate and healthy serving is for many foods, reported Carol Byrd-Bredbenner, Ph.D., R.D., of Rutgers University here and colleagues in the September issue of the Journal of the American Dietetic Association.

This "portion distortion" may be one reason that Americans are getting fatter, they asserted. The investigators defined portion distortion as perceiving large portion sizes as appropriate amounts to eat at a single eating occasion.

Their study of food-selection habits here that duplicated one done 20 years previously. College students took significantly larger portions of many foods than their counterparts did in 1984, the researchers found. In addition, the student's self-served portions rarely matched the single serving size indicated by nutritional labeling.

The study involved 177 college students (75% women). In 2003, participants were asked to serve themselves typical portions of eight foods at breakfast, including cereal , toast, and orange juice, or six foods at lunch or dinner, including tuna salad, tossed salad, and soda. The portions selected were weighed and compared with results of the 1984 study.

The participants, who did not know the purpose of the study, served themselves alone, and scales for weighing the food that remained on the buffet were hidden from view, in order to reduce the likelihood that outside influences would affect the portion sizes selected. For the same reason, a wide variety of sizes of bowls, plates, and cups were available to choose from.

The portion sizes selected for cornflakes, milk for the cereal, orange juice, and fruit salad were significantly larger in 2003 than in 1984, the study found.

For example, 2003 study participants selected an average of nearly 44 grams of cornflakes, compared with an average of 37 grams 20 years ago. Similarly, an average of 272 grams of orange juice was selected in 2003, versus 190 grams in 1984. Finally, 164 grams of fruit salad was the norm in 2003 compared with 123 grams two decades ago. (P<.05 for all.)

Only 45% of the portions selected at breakfast came within 25% of the single-serving size indicated by product nutrition labeling. For lunch and dinner, that figure was even lower-32%.

"Portion sizes of individually packaged and ready-to-eat prepared foods have increased as well as the portion sizes served at fast-food, chain, and privately owned restaurants," the authors said. "Consumers may now perceive these larger portion sizes as an appropriate amount to eat at a single eating occasion, and thus experience portion distortion."

"Body weights have increased in parallel with increasing portion sizes, suggesting that portion distortion may be a primary contributor to obesity in the United States," the authors said.

Health and nutrition professionals should be aware that the huge servings typical of the marketplace may have considerable influence on the portion sizes individuals view as typical and appropriate, even when cooking and eating at home, the authors said.

"Food and nutrition professionals also must remain cognizant that clients' typical portion sizes likely differ from reference portions, and provide clients with instruction on how to measure portion sizes accurately," they added.

There's not much chance that the trend toward large portion sizes will reverse anytime soon, the authors said. "If anything, recent additions to popular eating establishments' menus suggest that the trend toward larger portions will continue to grow," they said.

The authors urged lawmakers to require the food industry to revise nutrition labeled and packaging to be less misleading. The amount in a single-unit container should be equivalent to one serving, they said.

On a more positive note, the portions of some foods students selected in 2003 were smaller than those of 20 years ago, most notably sugar on cereal (6 grams versus eight grams) and salad dressing (16 grams versus 20 grams; P<.05 for both foods).

"The message that even healthful foods (i.e. tossed salad) may contain excessive energy when high-fat items (i.e. salad dressing) are added may have become well understood during the past two decades," the authors concluded.