CHICAGO — While Americans might be eating many of the same foods they ate three decades ago, the “how” and “who” of preparing this food has changed, according to market researcher The NPD Group.

“The fast and hectic pace of the lives we lead has had the single greatest impact on this country’s eating behaviors,” said Mark East, president of The NPD Group’s North American food and beverage unit. “It’s clear by the changes we’ve observed over the past 30 years that the Google generation wants things now.”

Thirty years ago, 72% of main dishes at dinner were homemade, and today this number is down to 59%. Many consumers now are preferring ready-to-eat and frozen foods or assembling a meal instead of preparing it. The sandwich is still one of the top foods consumed as it was 30 years ago, but today that sandwich is more likely to be ready-to-eat, frozen or prepared by a restaurant or food service outlet as opposed to being prepared by someone in the household as it was back then.

The NPD Group’s National Eating Trends also found that the average number of food items used per meal decreased from 4.44 in the 1980s to 3.5 in 2010. Year-round grilling, microwave ovens and slow cookers have helped make cooking more convenient with the per cent of meals cooked by the microwave doubling since the 1980s and the number of households using a slow cooker at least once in a two-week period jumping 67% from the 1980s to 2010. In addition, more than one-third of households use the grill to make at least one meal in a two-week period. The use of slow cookers is expected to increase by 16% during the next decade, and grilling is expected to grow by 11%.

“Americans have an ever increasing need for convenience when it comes to eating,” Mr. East said. “We fully expect this trend to continue as ready-to-eat meals prepared outside the home and eating in-home, fresh, and frozen foods are all forecasted to grow notably in the next decade.”