As Americans are increasingly staying home for dinner, they're also using their microwave ovens more, according to leading market research company NPD Group, which recently released this year's edition of Eating Patterns in America.

In its annual compilation of research on the US food and beverage market, the report found that microwave oven usage increased in 2009 after being relatively flat for the past 20 years, suggesting that Americans are not only eating in and going out less, but that they're also cooking less.

"We're using our microwaves to warm and heat more, but not to prepare more dishes from scratch," said Harry Balzer, chief industry analyst at The NPD Group and author of the report.

The market research revealed that Americans were using their stove tops less in favor of the microwave oven to get their meals ready. About 20 percent of meals eaten at home in the last 20 years were prepared using the microwave oven, a figure which has increased by 10 percent in the last year, according to the report.

The proportion of main meals prepared on a stove top declined to 33 percent in 2009 compared to 52 percent in 1985.

Recent market research has also shown that sales of pre-prepared meals in supermarkets has risen considerably in the last year, with pre-prepared frozen foods and ethnic foods as key categories with increasing market share.