Chances are there is a lot more food there than on a comparable plate two decades ago, says a report in the Jan. 22 issue of the Journal of the American Medical Association.
"Between 1977 and 1996, food portion sizes increased both inside and outside the home for all categories except pizza," the report says.
That conclusion comes from two major studies: the National Food Consumption Survey, which gave information on 1977 portion sizes, and the Continuing Survey of Food Intake, which gave data for 1989 and 1996.
The surveys contained information about specific food items -- salty snacks, desserts, soft drinks and french fries -- and eating location -- home, restaurant or fast food outlet.
Fast food establishments such as McDonald's and Burger King might have led the way with their "supersize" portions, but the increase was evident everywhere, says Samara Joy Nielsen, a graduate student in nutritional epidemiology at the University of North Carolina, who did the study with Dr. Barry M. Popkin, a professor of nutrition there.
"Fast food establishment servings are larger, and they have increased at home as well," she says. "It is hard to say which came first, but the point is that it is happening in both locations."
The results of the study are presented both in terms of ounces of food and as the amount of energy contained in food, in calories. For example, the energy in salty snacks increased by 93 calories and the size increased from 1 ounce to 1.6 ounces.
Similarly, a hamburger serving increased from 5.7 to 7 ounces, or 97 calories; a serving of french fries increased from 3.1 to 3.6 ounces, or 68 calories; and a serving of Mexican food increased from 6.3 to 8 ounces, or 133 calories.
"Since an added 10 kilocalories a day of unexpended energy is equivalent to an extra pound of weight per year, it is easy to see the potential impact of large increases in portion sizes," the report says. (What scientists call kilocalories, most of us call calories.)
While there has been a lot of emphasis on heart-healthy eating -- avoiding fatty foods and so on -- much less has been said about the sheer quantity of food consumed, Nielsen says.
"We need to be telling people that it's not just what you are eating but also the quantity of food you are eating," she says.
"I call it portion distortion," says Wahida Karmally, an associate research scientist at Columbia University and a spokeswoman for the American Dietetic Association.
"Eating habits have created a toxic environment for the American population," Karmally says. "Obesity rates have gone up to epidemic proportions and that has a tremendous impact on health. The effect on hypertension, diabetes and heart disease is quite evident."
People need to be aware of the effect of larger portions on their weight, and to make sure their children know it too, she says. "Parents have a responsibility to show children how to eat," Karmally says. "It shouldn't be the old strategy of 'Clean up your plate.'"
You can learn more about obesity, its problems and how to avoid it, from the National Institute of Diabetes and Digestive and Kidney Diseases. Get tips on eating right from the American Dietetic Association.