"Millennials will diet more as they age, but the core dieters in this country are Boomers," said Harry Balzer, author of "Eating Patterns in America" and chief industry analyst for NPD. "But fewer of us are dieting. Americans are looking for other ways to define health."

This is not just a short-term trend, according to NPD's National Eating Trends Service, which examines top-of-mind dieting and nutrition along with actual eating and drinking habits. Just 19% of adults report being on a diet in the last year, down from the 1991 peak of nearly 30% who reported being on a diet during a typical two-week period.

While U.S. consumers are dieting less overall, as individual adults age, they are more likely to be on a diet. Additionally, despite the lower dieting rate, 57% of adults report that they would like to lose 20 pounds.

"Dieting is not the only way to address your health these days," Balzer said. "Avoiding foods with harmful substances and adding foods with beneficial ingredients remain an appealing way to deal with our health rather than just dieting.".

Some 72% of adults eat reduced-fat foods, nearly 45% regularly eat foods with whole grains, and 24% include organic foods and beverages in their diet.

"Dieting is difficult and requires a change in habits. Eating healthy or adding good foods in your diet is much easier," Balzer concluded.