Among those who eat fast food, 44 percent do so at lunch and 42 percent at dinner. Men are more likely to grab fast food at lunch; women are more likely to snack on it.

The most enthusiastic consumers are 20 to 39 years old: 45 percent of them eat fast food on any given day. That figure declines sharply with age, to 38 percent among people 40 to 59, and to 24 percent among those over age 60.

Liz Weinandy, a staff dietitian at the Ohio State University Medical Center who was not involved in writing the report, said that the high rate among 20- to 39-year-olds was particularly troubling.