Study confirms that food portion sizes increased in U.S. over two decades

CHAPEL HILL — Between 1977 and 1996, portion sizes for key food groups grew markedly in the United States, not only at fast-food restaurants but also in homes and at conventional restaurants, a new study shows.

The observation is one more indication of broad changes in the way Americans eat and another reason for the widespread, unhealthy rise in obesity among U.S. children and adults, University of North Carolina at Chapel Hill researchers say. It is believed to be the first documentation that at any given meal, on average, the typical American eats more than he or she did only a few decades ago.

A report on the findings appears in Wednesday’s issue (Jan. 22) of the Journal of the American Medical Association. Authors are nutrition doctoral student Samara Joy Nielsen and Dr. Barry M. Popkin, professor of nutrition at the UNC schools of public health and medicine and a fellow at the Carolina Population Center.

“Many people have thought that portion sizes might be on the rise, but until now, there have been no empirical data to document actual increases,” Nielsen said. “We think this is important information not only because it documents this trend, but also because obesity presents a growing health threat both in the United States and abroad.”

The research involved analyzing nationally representative data from the 1977-78 Nationwide Food Consumption Survey and three separate Continuing Surveys of Food Intake by Individuals. The sample consisted of 63,380 people ages 2 and older.

Nielsen and Popkin calculated the average amounts of specific foods eaten in both calories and ounces at home, in restaurants and in fast-food restaurants for each survey year.

“Portion sizes varied by food source, with the largest being consumed at fast-food establishments and the smallest at restaurants,” she said. “Between 1977 and 1996, portion sizes increased for salty snacks, desserts, soft drinks, fruit drinks, French fries, hamburgers, cheeseburgers and Mexican food.”

Such increases were large, Nielsen said.

“The quantity of salty snacks increased by 93 calories or 0.6 ounces, soft drinks by 49 calories or 6.8 ounces, hamburgers by 97 calories or 1.3 ounces, French fries by 68 calories or 0.5 ounces and Mexican food by 133 calories, or 1.7 ounces,” she said.

Both scholars and policymakers have discussed “supersizing” as a critical problem in the marketing of food by the fast-food sector, Popkin said.

“While our research did not exactly study ‘supersizing,’ it shows its impact is seen in the very large portion size increases in the past decade,” he said.

When combined with less physical activity than in decades past, greater energy consumption significantly raises the risk of heart disease, stroke, hypertension, diabetes and other health threats, Popkin said. Related recent UNC findings were that all age groups ate more restaurant food — including fast food — than a generation ago.

“Dietary patterns are rapidly shifting in the United States, and these changes are important

contributors to the growing epidemic of obesity and diabetes facing Americans,” he said. “Clearly the problem is that Americans are eating too much food. The problem is the combination of a rapid increase in eating at fast-food establishments, an increase in selected foods such as cheeseburgers and soft drinks and the portion sizes we report in this new study.”

UNC researchers also earlier found large increases in snack eating, Nielsen said. In 1977, for example, snacks produced 11.3 percent of the average American’s energy intake, while by 1996 that figure had climbed to 17.7 percent, which is more than a 50 percent increase.

“While older Americans continue to snack less than other age groups, they experienced the largest increase in snacking, a jump from 7.7 percent of energy from snacks to 14 percent, which is almost double,” she said. “Among people under age 39, pizza and salty snack consumption rose as much as 143 percent.”

The U.S. Department of Agriculture supported the surveys, which involved interviewing Americans about what and where they and their children had eaten over the previous few days and where the food they ate came, from such as stores and vending machines.