For the study, being published this month in The Journal of the American Dietetic Association, researchers taped 28 days of prime-time television as well as Saturday-morning programming on the four major broadcast networks. They identified 800 foods promoted in 3,000 ads and used a nutritional software program to analyze the content of the items, comparing the foods’ nutritional values with the government’s food guide pyramid and recommended daily intake values for various nutrients.

The study assumed that individuals were limiting themselves to 2,000 calories a day of the advertised foods, said the lead author, Michael Mink, an assistant professor of health sciences at Armstrong Atlantic State University in Savannah, Ga.

A 2,000-calorie diet made up solely of foods from commercials would provide too much cholesterol, saturated fat and salt, which are associated with chronic disease, Dr. Mink said, but not nearly enough nutrients like iron, calcium or vitamins A, D and E.

“Just one advertised food item by itself will provide, on average, three times your daily recommended servings of sugar and two and half times your daily recommended servings of fat,” he said. “That means one food item could give you three days’ worth of sugar.”