Researcher Documents Growth of US Portions - and US Waistlines

American Institute for Cancer Research
Thursday, 17 July 2003

Studies Now Confirm That Portions Have Gotten Bigger; Allow Scientists to Measure the Effect of Oversize Portions on Overeating

A recent flurry of scientific research on US portion sizes has transformed two previously unconfirmed beliefs into hard scientific facts: US portion sizes have never been bigger, and bigger portions encourage overeating - by as much as 56 percent.

Speaking at a press conference at the American Institute for Cancer Research (AICR) International Research Conference, Dr. Barbara Rolls of the Pennsylvania State University explained how emerging science is allowing scientists to definitively answer lingering questions about the role of portion size in the obesity epidemic.

She outlined the tools that researchers now use to track the growth of portion size in the United States and to pinpoint the precise degree by which these portions induce overeating. Her remarks were adapted from the text of her review called "The Supersizing of America: Portion Size and the Obesity Epidemic," which appeared in a recent issue of Nutrition Today.

"As recently as three years ago, health experts concerned about the growth of US portions and its effect on health were forced to cite anecdotal examples and issue warnings based on educated guesses, because the science simply hadn't been done," she said.

AICR was one such health organization, which began to raise awareness about portion sizes in 1999 in dramatic but unscientific ways. In 2000, AICR contacted colleagues in Poland, France and Mexico and asked them to measure the size and weight of foods indigenous to those cultures: the bagel, the croissant and the quesadilla. AICR experts then compared those measurements to versions of these foods found in US markets, and found that the American versions had ballooned in size, weight and calorie content.

Today, however, AICR and other health experts can point to the concrete conclusions of studies now being published in scientific journals like the Journal of the American Medical Association, the American Journal of Clinical Nutrition, the Journal of the American Dietetic Association, and many others.

Dr. Rolls, who was the first researcher to acquire an NIH grant to study the role of portion size on calorie intake, outlined some of the findings that have come to light only within the past few months and years.

New Research Demonstrates Growth of Portions

A study published last year in the Journal of the American Dietetic Association showed that the portion sizes of commercially available foods and beverages have increased. In 1955, a single order of French fries weighed in at 2.4 ounces. Today, an average single serving is 7.1 ounces - a nearly 200 percent increase.

According to data published this year in the Journal of the American Medical Association, individual portions of snacks, soft drinks, hamburgers, French fries and Mexican food have increased significantly over the past 20 years. These increases have occurred both in and out of the home.

A study published this year in the Journal of the American Dietetic Association suggests that much of the previously observed growth has happened recently. According to the study, the portions of certain foods - pasta, soft drinks, cereal, beer, coffee and others - have increased dramatically in just 5 years time.

New Research Demonstrates that Bigger Portions Increase Consumption

Dr. Rolls' recent work as holder of the Guthrie Chair in Nutrition at Penn State has focused on determining the extent to which portion sizes affect calorie intake, and she and her colleagues have been using controlled trials to gauge how different portions of different foods influence how much people eat.

In a study published in the American Journal of Clinical Nutrition, Dr. Rolls and her colleagues tested how subjects responded to 4 different portions of macaroni and cheese served on different days. Study participants consumed 30 percent more calories on days when they were served the largest portion. Fewer than half of the respondents noticed that there were differences in the portions they were served.

In another study, published in the journal Appetite, subjects were offered differently sized submarine sandwiches over 4 different days: 6-inch, 8-inch, 10-inch, and 12-inch. When served the 12-inch sandwich compared to the 6-inch, women consumed 31 percent more calories and men consumed 56 percent more.

One study highlighted the fact that when people unthinkingly consume bigger portions they are not likely to compensate for the extra calories later in the day. In the study, published in the journal Appetite, subjects were served a mid-afternoon snack consisting of differently sized bags of potato chips. In the study, a larger bag of potato chips (170 grams vs. 85 grams) induced women to consume 18 percent more calories, and men to consume 37 percent more. When dinner was served several hours later, subjects did not adjust their intakes to compensate for the extra calories.

Several other controlled studies have focused on how the portion sizes of various foods (pasta, cooking oil, candy, popcorn) affect consumption in the short term. Now a new study suggests that portion size can induce sustained overeating over longer periods of time. In a controlled study, published in the Federation of American Societies for Experimental Biology Journal, researchers increased the portion sizes of all foods eaten by a group of subjects over 2 days' time. When portions were 50 percent larger than baseline, calorie intake increased by 16 percent. When portions served were 100 percent larger, calorie intake increased by 26 percent.

Researcher Issues Call to Action

"It's taken a long time to get here, and there's much work still to be done, but we are now beginning to get the kind of hard numbers we can use," Dr. Rolls said. "In laboratories and clinics throughout the country, researchers are working to bring the hidden influence of portion size to light.

"And that research indicates that everyone - men and women, those at a healthy weight and those who need to lose a few pounds - is susceptible to the influence of portion size. Clearly, the continuing rise in the rates of obesity calls for urgent action on the part of scientists, the private sector, and the public."

Dr. Rolls stressed, however, that more than increased portion size alone is contributing to the American obesity epidemic. In particular, Dr. Rolls believes that the consumption of large portions of food that are themselves high in calories and in fat plays a central role.

"Conversely, large portions of foods low in calories and fat such as vegetables, fruits and broth-based soups can aid weight management by providing satisfying portions with fewer calories."

For more information, or to contact American Institute for Cancer Research, see their website at: www.aicr.org

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